Java Technical

Spring Transaction

2014-09-12T22:09:00.000+05:30

Just Small project done for testing Spring Transaction. For future reference I am writing this Blog.

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>SpringSecurity</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
   <servlet-name>spring-security</servlet-name>
   <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  </servlet>
  <servlet-mapping>
   <servlet-name>spring-security</servlet-name>
   <url-pattern>*.html</url-pattern>
  </servlet-mapping>
  <listener>
  <listener-class>org.springframework.web.context.ContextLoaderListener
  </listener-class>
 </listener>
 
        <!-- Loads Spring Security config file -->
 <context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>
   /WEB-INF/spring-security-servlet.xml
  </param-value>
 </context-param>
 
</web-app>

spring-security-servlet.xml


<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:tx="http://www.springframework.org/schema/tx"
 xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd">
 
 <context:component-scan base-package="com.prajith.*" />
 
 <bean
   class="org.springframework.web.servlet.view.InternalResourceViewResolver">
   <property name="prefix">
  <value>/view/</value>
   </property>
   <property name="suffix">
  <value>.jsp</value>
   </property>
 </bean>
   
    <!-- Initialization for data source -->
   <bean id="dataSource" 
      class="org.springframework.jdbc.datasource.DriverManagerDataSource">
      <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
      <property name="url" value="jdbc:mysql://localhost:3306/maverick"/>
      <property name="username" value="root"/>
      <property name="password" value="*******"/>
   </bean>

   <!-- Initialization for TransactionManager -->
   <bean id="transactionManager" 
      class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
      <property name="dataSource"  ref="dataSource" />    
   </bean>
 
  <!-- enable the configuration of transactional behavior based on annotations -->
    <tx:annotation-driven transaction-manager="transactionManager"/><!-- a PlatformTransactionManager is still required -->
</beans>

For making annotation driven need to add the code.

<tx:annotation-driven transaction-manager="transactionManager"/>

Transaction manager changes with the interacting platform.

Platform                     TransactionManager or PlatFormTransactionManager
JDBC                     org.springframework.jdbc.datasource.DataSourceTransactionManager
JTA                        org.springframework.transaction.jta.JtaTransactionManager
Hibernate                    org.springframework.orm.hibernate3.HibernateTransactionManager

Types of Probagation defined in the Spring Docs

MANDATORY :Support a current transaction, throw an exception if none exists.

NESTED :Execute within a nested transaction if a current transaction exists, behave like PROPAGATION_REQUIRED else.NEVER :Execute non-transactionally, throw an exception if a transaction exists.NOT_SUPPORTED : Execute non-transactionally, suspend the current transaction if one exists.REQUIRED : Support a current transaction, create a new one if none exists.REQUIRES_NEW : Create a new transaction, suspend the current transaction if one exists.SUPPORTS :

Support a current
transaction, execute non-transactionally if none exists.

SpringTransactionTest.java

package com.prajith.web.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

import com.prajith.web.service.EmployeeServiceIntf;

@Controller
public class SpringTransactionTest {

 @Autowired
 EmployeeServiceIntf employeeServiceIntf;
 
 public void setEmployeeServiceIntf(EmployeeServiceIntf employeeServiceIntf) {
  this.employeeServiceIntf = employeeServiceIntf;
 }
 
 @RequestMapping(value="/sqltransactionTest")
 public ModelAndView testTransaction(){
  ModelAndView model= new ModelAndView("admin");
  try{
   employeeServiceIntf.testTransaction(); 
  }catch(Exception e){
   System.out.println(e);
  }
  return model;
 }
}

EmployeeServiceIntf.java

package com.prajith.web.service;

public interface EmployeeServiceIntf {
 public void testTransaction() throws Exception;
}

EmployeeServiceImpl.java


package com.prajith.web.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.prajith.web.dao.EmployeeDAOIntf;
import com.prajith.web.domain.Employee;
import com.prajith.web.domain.Salary;

@Service
public class EmployeeServiceImpl implements EmployeeServiceIntf {

 @Autowired
 private EmployeeDAOIntf employeeDAOIntf;
 
 public void setEmployeeDAOIntf(EmployeeDAOIntf employeeDAOIntf) {
  this.employeeDAOIntf = employeeDAOIntf;
 }

 @Transactional// autoscan makes this method transactional
 public void testTransaction() throws Exception {
  // TODO Auto-generated method stub
  
  Employee emp=new Employee();
  emp.setEmpName("prajith");
  
  Salary sal =new Salary();
  sal.setEmpNo(1);
  sal.setSalary(20000);
  employeeDAOIntf.insertEmp(emp);
  employeeDAOIntf.insertSalary(sal);
  
  Employee emp1=new Employee();
  emp1.setEmpName("pooja");
  
  Salary sal1 =new Salary();
  sal1.setEmpNo(3);//purposefully kept so that DB will throw error.
  sal1.setSalary(204440);
  employeeDAOIntf.insertEmp(emp1);
  employeeDAOIntf.insertSalary(sal1);
 }

}

EmployeeDAOIntf


package com.prajith.web.dao;

import com.prajith.web.domain.Employee;
import com.prajith.web.domain.Salary;

public interface EmployeeDAOIntf {
 public void insertEmp(Employee emp) throws Exception;
 public void insertSalary(Salary emp) throws Exception;
}

EmployeeDAOImpl


package com.prajith.web.dao;

import javax.sql.DataSource;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

import com.prajith.web.domain.Employee;
import com.prajith.web.domain.Salary;

@Repository
public class EmployeeDAOImpl implements EmployeeDAOIntf{

 String sql1 = "insert into Employee (empname) values (?)";
 String sql2 = "insert into Salary (empid, Salary) values (?, ?)";
 @Autowired
 private DataSource dataSource;
 
 public DataSource getDataSource() {
  return dataSource;
 }

 public void setDataSource(DataSource dataSource) {
  this.dataSource = dataSource;
 }

 public void insertEmp(Employee emp) throws Exception {
  // TODO Auto-generated method stub
  System.out.println("Employee Insertion");
  JdbcTemplate jt=new JdbcTemplate(dataSource);
  jt.update(sql1,emp.getEmpName());
  System.out.println("--> Employee data inserted : " );
 }

 public void insertSalary(Salary sal) throws Exception {
  // TODO Auto-generated method stub
  System.out.println("Salary Insertion");
  JdbcTemplate jt=new JdbcTemplate(dataSource);
  jt.update(sql2,sal.getEmpNo(),sal.getSalary());
  System.out.println("salary inserted successfully : ");
 }

}

Converting Java object into JavaScript object

2014-09-07T00:40:00.000+05:30

Recently I had a requirement to change a java object into JavaScript object when the request is submitted and response is received. I dint want to make a ajax call because the data was available when I received the response but i was not able to get that in JavaScript object from the request. I did Google and found some of the possible solution as per the link. The below code from the site was workable but I had a complex object


<script>  
    var myMap = {  
      <c:forEach items="${theMap}" var="item" varStatus="loop">  
        ${item.key}: '${item.value}' ${not loop.last ? ',' : ''}  
      </c:forEach>  
    };  
</script>

and it require many levels of iteration and the creation of the same object with the above logic was difficult and thus it was better to go for ajax than creating the JavaScript object from the request.

Then i realized the object we are trying to create using the above logic is exactly same as the json object then perhaps sending json string and trying to convert that will be much more easier than doing the above logic. It was much more easier than the above logic so am pasting my test project for any one who require such requirements in future.

Simple pojo trying to convert.
Employee.java


package springapp.domain;

public class Employee {

    private String name;
    private String age;
    private Address address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAge() {
        return age;
    }
    public void setAge(String age) {
        this.age = age;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "Employee [name=" + name + ", age=" + age + ", address="
                + address + "]";
    }
    
}

Address.java


package springapp.domain;

public class Address {

    private String street;
    private String city;
    public String getStreet() {
        return street;
    }
    public void setStreet(String street) {
        this.street = street;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }
    @Override
    public String toString() {
        return "Address [street=" + street + ", city=" + city + "]";
    }
    
}

class converting List of employee to json object and setting into request scope

JspVariableTest.java


package springapp.web;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import junit.framework.Test;

import org.codehaus.jackson.map.ObjectMapper;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.Controller;

import springapp.domain.Address;
import springapp.domain.Employee;


public class JspVariableTest implements Controller{

    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        ModelAndView view=new ModelAndView("jspVariabletest");
        List<Employee> empList=new ArrayList<Employee>();
        
        Employee emp=new Employee();
        emp.setAge("27");
        emp.setName("prajith");
        Address add=new Address();
        add.setStreet("Testing");
        add.setCity("Mumbai");
        emp.setAddress(add);
        
        Employee emp2=new Employee();
        emp2.setAge("27");
        emp2.setName("pooja");
        Address add2=new Address();
        add2.setCity("chennai");
        add2.setStreet("2nd street");
        emp2.setAddress(add2);
        
        empList.add(emp);
        empList.add(emp2);
        
        Map<String,Object> map=new HashMap<String,Object>();
        map.put("empList", empList);
        view.addObject("empMap",map);//adding the map object to the request 
        
        ObjectMapper mapper=new ObjectMapper();// jackson lib for converting to json
        String empMapString=mapper.writeValueAsString(map);// json string
        view.addObject("empMapString",empMapString);
        
        return view;
    }
}

Now simple jsp to convert java object to JavaScript. I have kept actual java Object and json Object to show the difference how it assigns to the JavaScript variable.

jspVariabletest.jsp


<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<script>
var empMap="${empMap}";// acutal java object assigning to javascript variable 
var empObj=${empMapString};//actual jsonString assigning to javascript variable

</script>
<c:forEach items="${empMap}" var="entry">
    Key = ${entry.key}, value = ${entry.value}<br>
</c:forEach>
</body>
</html>

Now i have debugged the code in google chrome developer tool and attached the screen shot of the two objects we have created and assigned to JavaScript variable.

The java Map object we are getting in string which i have assigned to empMap variable of javascipt and the json object we are getting as JavaScript object which I have assigned to empObj. Which is ready to use. If we apply the other logic i have got from the other site, it would have took long time to change this simple object to JavaScript object which is not feasible for changing complex object.

HttpServletRequestWrapper class usage or Modify HttpServletRequest Object including header information

2013-11-28T02:52:00.000+05:30

Recently i came across a requirement where for time being I need to send some information in header of HttpServletRequest object. Setting it in browser level was not a option as we cant setup the header information everytime and in every system.

So did browsing little bit and found a solution. Also came to know many people are looking for it so would like to share the code for doing a work around using HttpServletRequestWrapper.

In the below project, going to insert value in the HttpServletRequest object as parameter and later modifying the object in the java code to get the value using method getHeader() of HttpServletRequest object.

Project Name : EditHeaderVariable

First create a dynamic web project with the name you would like to give and put necessary jar files. I have made it as spring mvc project using maven. Giving below the dependency requirements in pom.xml file.

pom.xml

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">  
  <modelVersion>4.0.0</modelVersion>  
  <groupId>EditHeaderVariable</groupId>  
  <artifactId>EditHeaderVariable</artifactId>  
  <version>0.0.1-SNAPSHOT</version>  
  <name>EditHeaderVariable</name>  
  <description>EditHeaderVariable</description>  
  <dependencies>  
       <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-core</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
            <scope>compile</scope>  
       </dependency>  
       <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-web</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
            <scope>compile</scope>  
       </dependency>  
       <dependency>  
            <groupId>org.springframework</groupId>  
            <artifactId>spring-webmvc</artifactId>  
            <version>3.2.4.RELEASE</version>  
            <type>jar</type>  
            <scope>compile</scope>  
       </dependency>  
  </dependencies>  
 </project>

web.xml

Adding spring DispatcherServlet and other filter as required.

 <?xml version="1.0" encoding="UTF-8"?>  
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  
  <display-name>EditHeaderVariable</display-name>  
  <welcome-file-list>  
   <welcome-file>index.jsp</welcome-file>  
  </welcome-file-list>  
  <servlet>  
   <servlet-name>editHeader</servlet-name>  
   <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><!--  
   <init-param>  
    <param-name>contextConfigLocation</param-name>  
    <param-value>/WEB-INF/spring/dispatcher-config.xml</param-value>  
   </init-param>  
   --><load-on-startup>1</load-on-startup>  
  </servlet>  
   <context-param>  
      <param-name>contextConfigLocation</param-name>  
      <param-value>/WEB-INF/editHeader-servlet.xml</param-value>  
  </context-param>  
  <servlet-mapping>  
   <servlet-name>editHeader</servlet-name>  
   <url-pattern>*.html</url-pattern>  
  </servlet-mapping>  
  <listener>  
   <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
  </listener>  
  <filter>  
       <filter-name>modifyRequestObjectFilter</filter-name>  
       <filter-class>com.prajith.filter.ModifyRequestObjectFilter</filter-class>  
  </filter>  
  <filter-mapping>  
       <filter-name>modifyRequestObjectFilter</filter-name>  
       <url-pattern>/*</url-pattern>  
  </filter-mapping>  
 </web-app>

editHeader-servlet.xml

enabling autoscan feature of the spring.

 <beans xmlns="http://www.springframework.org/schema/beans"  
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
      xmlns:context="http://www.springframework.org/schema/context"  
      xsi:schemaLocation="http://www.springframework.org/schema/beans   
      http://www.springframework.org/schema/beans/spring-beans-2.5.xsd  
      http://www.springframework.org/schema/context  
      http://www.springframework.org/schema/context/spring-context-2.5.xsd">  
      <context:component-scan base-package="com.prajith" />  
      <bean id="viewResolver"  
           class="org.springframework.web.servlet.view.InternalResourceViewResolver" >  
       <property name="prefix">  
        <value>jsp/</value>  
       </property>  
       <property name="suffix">  
        <value>.jsp</value>  
       </property>  
     </bean>  
 </beans>

index.jsp

welcome page for the application where we are giving option to enter some value in the form which we want to get in the header of the HttpServletRequest object created on submission.

 <%@ page language="java" contentType="text/html; charset=ISO-8859-1"  
   pageEncoding="ISO-8859-1"%>  
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
 <html>  
 <head>  
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">  
 <title>Insert title here</title>  
 </head>  
 <body>  
      <form method="post" action="testheader.html">  
           write the header value to get : <input id="headerTest" name="headerTest" type="text" />  
           <input type="submit" value="submit"/>  
      </form>  
 </body>  
 </html>

result.jsp

This jsp is just to redirect 2 time without wasting time on again clicking and redirecting. This jsp is also to show that the second HttpServletRequest object does't contain any information passed in earlier HttpServletRequest object but still we are able to get the value of the earlier submitted request in the getHeader() method of the new HttpServletRequest object.

 <%@ page language="java" contentType="text/html; charset=ISO-8859-1"  
   pageEncoding="ISO-8859-1"%>  
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
 <html>  
 <head>  
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">  
 <title>Insert title here</title>  
 </head>  
 <body>  
 <%response.sendRedirect("/EditHeaderVariable/resultCheck.html");%>  
 </body>  
 </html>

result2.jsp

This jsp shows the value which we submitted in the first request from the index.jsp by getting the value from the getHeader() method of the HttpServletRequest object from session so that we need not submit the header information every time we need.

 <%@ page language="java" contentType="text/html; charset=ISO-8859-1"  
   pageEncoding="ISO-8859-1"%>  
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
 <html>  
 <head>  
 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">  
 <title>Insert title here</title>  
 </head>  
 <body>  
 ${message}  
 </body>  
 </html>

HeaderController.java

This controller is for just printing and redirecting to the correct jsp resource.

 package com.prajith.httpservlet;  
 import javax.servlet.http.HttpServletRequest;  
 import javax.servlet.http.HttpServletResponse;  
 import org.springframework.stereotype.Controller;  
 import org.springframework.web.bind.annotation.RequestMapping;  
 import org.springframework.web.servlet.ModelAndView;  
 @Controller  
 public class HeaderController {  
      @RequestMapping("/testheader")  
      public ModelAndView testHeader(HttpServletRequest request, HttpServletResponse response){  
           System.out.println("testheader");  
           System.out.println(request.getHeader("headerTest"));  
           return new ModelAndView("result");  
      }  
      @RequestMapping("/resultCheck")  
      public ModelAndView resultCheck(HttpServletRequest request, HttpServletResponse response){  
           System.out.println("resultCheck");  
           System.out.println(request.getHeader("headerTest"));  
           return new ModelAndView("result2","message",request.getHeader("headerTest"));  
      }  
 }

ModifyRequestObjectFilter.java

This filter has been created so that we can modify the request object before reaching the controller. On reaching the controller, the controller gets modified HttpServletRequest object. In the below code you can see we have overridden the dofilter method of the filter interface and changed the ServletRequest object by casting the new class ModifyRequest which extends to HttpServletRequestWrapper class to ServletRequest object.

 package com.prajith.filter;  
 import java.io.IOException;  
 import javax.servlet.Filter;  
 import javax.servlet.FilterChain;  
 import javax.servlet.FilterConfig;  
 import javax.servlet.ServletException;  
 import javax.servlet.ServletRequest;  
 import javax.servlet.ServletResponse;  
 import javax.servlet.annotation.WebFilter;  
 import javax.servlet.http.HttpServletRequest;  
 /**  
  * Servlet Filter implementation class ModifyRequestObjectFilter  
  */  
 @WebFilter("/ModifyRequestObjectFilter")  
 public class ModifyRequestObjectFilter implements Filter {  
   /**  
    * Default constructor.   
    */  
   public ModifyRequestObjectFilter() {  
     // TODO Auto-generated constructor stub  
   }  
      /**  
       * @see Filter#destroy()  
       */  
      public void destroy() {  
           // TODO Auto-generated method stub  
      }  
      /**  
       * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)  
       */  
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {  
           // TODO Auto-generated method stub  
           // place your code here  
           // pass the request along the filter chain  
           try{  
                request=(ServletRequest)new ModifyRequest((HttpServletRequest)request);  
                chain.doFilter(request, response);  
           }catch(Exception e){  
                System.out.println("error "+e);  
           }  
      }  
      /**  
       * @see Filter#init(FilterConfig)  
       */  
      public void init(FilterConfig fConfig) throws ServletException {  
           // TODO Auto-generated method stub  
      }  
 }

ModifyRequest.java

This class extends to HttpServletRequestWrapper class and overrides getHeader method. In this method we don't want to loose the originality of the method so we have coded as super.getHeader() which calls the parent class method and returns the value accordingly. In case the returned value is null then we are modifying the value to be returned as per our need.

This is not only to modity the getHeader() method but also can be used to modify other method of the HttpServletRequest as per our need.

 package com.prajith.filter;  
 import javax.servlet.http.HttpServletRequest;  
 import javax.servlet.http.HttpServletRequestWrapper;  
 public class ModifyRequest extends HttpServletRequestWrapper {  
      private HttpServletRequest req;  
      private String value=null;  
      public ModifyRequest(HttpServletRequest request) {  
           super(request);  
           req=request;  
           // TODO Auto-generated constructor stub  
      }  
      @Override  
      public String getHeader(String name){  
           value=super.getHeader(name);  
           if(value==null){  
                value=req.getParameter(name);  
                if(req.getParameter(name) !=null)  
                req.getSession().setAttribute(name, req.getParameter(name));  
           }  
           if(req.getParameter(name)==null){  
                value=(String)req.getSession().getAttribute(name);  
           }  
           return value;  
      }  
 }

project structure image :

maven library dependency:

Creating class inside Interface

2013-03-25T13:17:00.001+05:30

Recently i came to know that it is possible to create a class inside a interface. Its just for those people who don't know it is possible.

First we will be creating one interface as below.

TestClassinsideInterface.java

package com.lnt.test;

public interface TestClassinsideInterface {
void dofoo();
Ifoo ifoo=new Ifoo();

final class Ifoo implements TestClassinsideInterface{

    @Override
    public void dofoo() {
        // TODO Auto-generated method stub
        System.out.println("inside dofoo");
    }

}
}

Now creating class with main method to access the class inside interface.

TestInnerInterfaceClass.java

package com.lnt.test;

public class TestInnerInterfaceClass {


    public static void main(String[] args){
       TestClassinsideInterface testInterface=TestClassinsideInterface.ifoo;
       testInterface.dofoo();
    }
}

WebService using RESTeasy

2012-08-23T19:16:00.000+05:30

Webservice using RESTeasy is too simple. For creating the simple application we have to use the maven plugin or you can download the jar file and keep it inside the lib folder of the project.

First create a Dynamic Web Project and give any name you would like and then convert the project to a maven project and add the below dependency to the pom.xml.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

<groupId>RestEasy</groupId>

<artifactId>RestEasy</artifactId>

<version>0.0.1-SNAPSHOT</version>

<name>RestEasy</name>

<description>RestEasy</description>

<groupId>org.jboss.resteasy</groupId>

<artifactId>resteasy-jaxrs</artifactId>

</dependency>

</dependencies>

<build>

<artifactId>maven-compiler-plugin</artifactId>

</configuration>

</plugin>

</plugins>

</build>

</project>

Once you have done that then we need to create a class file with the name RestEasyTest.java. In this class file, @Path you need to specify for which this class need to be called as a mapping. then you need to create a method name showMessage and mention for what kind of call this method should respond. In the below example we are using the @Get. Now we need the parameter passed from the url to use in the method so we are using the {param} which will take the rest of the url after the "/test" and store it inside the string msg. Once this method is called we are returning the object of the Response.

RestEasyTest.java

package com.lnt.rest;

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.PathParam;

import javax.ws.rs.core.Response;

@Path("/test")

public class RestEasyExample {

@GET

@Path("/{param}")

public Response showMessage(@PathParam("param") String msg) {

String result = "Restful example : " + msg;

return Response.status(200).entity(result).build();

}

Configuration of the project to use the resteasy servlets are done at the web.xml

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"

id="WebApp_ID" version="3.0">

<display-name>RestEasy</display-name>

<welcome-file-list>

<welcome-file>index.html</welcome-file>

<welcome-file>index.htm</welcome-file>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.html</welcome-file>

<welcome-file>default.htm</welcome-file>

<welcome-file>default.jsp</welcome-file>

</welcome-file-list>

<context-param>

<param-name>resteasy.scan</param-name>

<param-value>true</param-value>

</context-param>

<context-param>

<param-name>resteasy.servlet.mapping.prefix</param-name>

<param-value>/rest</param-value>

</context-param>

<listener-class>

org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class>

</listener>

<servlet-name>resteasy-servlet</servlet-name>

<servlet-class>

org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>resteasy-servlet</servlet-name>

<url-pattern>/rest/*</url-pattern>

</servlet-mapping>

</web-app>

The listener org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap make sure that the REST services are registed and listened.

we are also providing the esteasy.servlet.mapping.prefix as "/rest" as the resteasy url pattern uses the /rest/*.

Now start the server and hit the link as

"http://localhost:8080/RestEasy/rest/test/hello%20prajith"

Result would be : Restful example : hello prajith

Reflections in Java

2012-07-12T15:34:00.000+05:30

Reflection is a feature in the Java programming language. It allows an executing Java program to examine or "introspect" upon itself, and manipulate internal properties of the program. For example, it's possible for a Java class to obtain the names of all its members and display them.

There are three steps that must be followed to use these classes.

1. Obtain a java.lang.Class object for the class that you want to manipulate.
2. Call method defined in the java.lang.Class to get the information about the class you want to manipulate.
3. Use the reflection API to manipulate the information

Example of Reflection feature.

Reflection :

package com.lnt.scjp;

import java.lang.reflect.*;

public class Reflection {

private int f1(Object p, int x) throws NullPointerException {

if (p == null)

throw new NullPointerException();

return x;

}

public static void main(String args[]) {

try {

Class cls = Class.forName("com.lnt.scjp.Reflection");

Method methlist[] = cls.getDeclaredMethods();

for (int i = 0; i < methlist.length; i++) {

Method m = methlist[i];

System.out.println("name = " + m.getName());

System.out.println("decl class = " + m.getDeclaringClass());

Class pvec[] = m.getParameterTypes();

for (int j = 0; j < pvec.length; j++)

System.out.println("param #" + j + " " + pvec[j]);

Class evec[] = m.getExceptionTypes();

for (int j = 0; j < evec.length; j++)

System.out.println("exc #" + j + " " + evec[j]);

System.out.println("return type = " + m.getReturnType());

System.out.println("-----");

}

} catch (Throwable e) {

System.err.println(e);

}

Output:

name = main

decl class = class com.lnt.scjp.Reflection

param #0 class [Ljava.lang.String;

return type = void

-----

name = f1

decl class = class com.lnt.scjp.Reflection

param #0 class java.lang.Object

param #1 int

exc #0 class java.lang.NullPointerException

return type = int

-----

In the above class we are printing the information of the same class using the Reflection feature of the java. In the above class we have only used the Method class under the java.lang.reflect package. There are other class which the same package provide for modifications. Which can be seen in the below link.

java.lang.reflect

Getting Spring WebApplicationContext object in Spring non managed bean

2012-06-15T20:16:00.002+05:30

In spring non managed bean its difficult to initialize the object using the spring framework. For this either you can use

ApplicationContext context = new ClassPathXmlApplicationContext("springapp-servlet.xml");

but using the above code loads the springapp-servlet.xml once again in the memory. In case of standalone application the above code will be fine but in case its a application running on server, loading the xml again will be costlier.So for getting the Spring WebApplicationContext object you can do as code marked in colored background.

package com.lntinfotech.office.common;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.web.context.WebApplicationContext;

import org.springframework.web.context.support.WebApplicationContextUtils;

import com.lntinfotech.office.dao.DAOImpl;

import com.lntinfotech.office.dao.DAOIntf;

import com.lntinfotech.office.domain.JiraTicket;

public class DWRImpl {

private Logger logger = LoggerFactory.getLogger(getClass());

public List<JiraTicket> jiraTicketDetails(String jiraTicket,

HttpServletRequest req, HttpServletResponse res) {

logger.debug("--> jiraTicketDetails(String name) " + jiraTicket);

List<JiraTicket> list = new ArrayList<JiraTicket>();

try {

WebApplicationContext applicationContext = WebApplicationContextUtils

.getRequiredWebApplicationContext(req.getSession()

.getServletContext());

logger.debug("--> applicationContext " + applicationContext);

DAOIntf daoIntf = (DAOImpl) applicationContext.getBean("daoIntf");

/* the above code gets the DAOImpl object via Spring IOC

* and its initializes all the other objects mapped in the spring WebApplicationContext

* removed unwanted code from the method......

} catch (Exception e) {

logger.error("Error : ", e);

return null;

}

logger.debug("<-- jiraTicketDetails(String name)");

return list;

}

Custom Converter in Struts 2.3 and utilizing using annotations

2012-06-15T19:38:00.002+05:30

In Struts we can write our own custom converter by extending to the StrutsTypeConverter and overriding the methods of the parent class. In the below example i have converted the string value received from the jsp to a Role object using the Struts annotation and the custom converter. I have not kept the Role class over here as you can convert this string to any object as per your requirement. Please don't forget to create a constructor in the POJO class as per the requirement other wise this converter wont work.

I have not overridden the convertToString method of the StrutsTypeConverter. This only because I am not using this conversion. It depends on the developer to override the methods according to the application need.

package com.lntinfotech.office.common;

import java.util.Map;

import org.apache.struts2.util.StrutsTypeConverter;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import com.lntinfotech.office.domain.Role;

import com.opensymphony.xwork2.conversion.TypeConversionException;

public class RoleConverter extends StrutsTypeConverter {

private Logger logger=LoggerFactory.getLogger(getClass());

@Override

public Role convertFromString(Map context, String[] values, Class toClass){

logger.debug("--> convertFromString String :"+values[0]);

Role role;

if (values != null && values.length > 0 && values[0] != null

&& values[0].length() > 0) {

try {

int id=Integer.valueOf(values[0]);

role=new Role(id);

} catch (Exception e) {

throw new TypeConversionException(e);

}

logger.debug("<-- convertFromString String :"+values[0]);

return role;

}

logger.debug("<-- convertFromString null");

return null;

}

@Override

public String convertToString(Map arg0, Object arg1) {

logger.debug("--> convertToString(Map arg0, Object arg1)");

// TODO Auto-generated method stub

return null;

}

In the above class we have created the a converter. So to use this we can use the Struts annotation. In the action class where you need this conversion to happen just annotate as

@TypeConversion and give the complete path of the converter. I have removed other variables and method as its not necessary for this example. At run time when we are getting the dynamic value from the frontend the below code will call the converter and convert the value to the Role object and process the form as per the code.

package com.lntinfotech.office.controller;

public class RegistrationAction extends ActionSupport {

private static final long serialVersionUID = 1L;

private Logger logger = LoggerFactory.getLogger(getClass());

private Role role;

public Role getRole() {

return role;

}

@TypeConversion(converter = "com.lntinfotech.office.common.RoleConverter")

public void setRole(Role role) {

this.role = role;

}

@Action(value = "/createuser", results = {

@Result(location = "registrationSuccess.jsp", name = "success"),

@Result(location = "registration.jsp", name = "input"),

@Result(location = "registration.jsp", name = "error") }, className = "registerUser")

public String createUser() {

logger.debug("--> createUser()");

//method code removed.

return "success";

}

Casting list of array of objects and utilizing the same in jsp

2012-06-15T18:58:00.000+05:30

In the below code the DAO class returns a list of objects. Now we need to iterate it and get the values of all the classes separately.

In the debug mode the list of array of object will look like as below.

Now to iterate this kind of list you need to first iterate as usual list and then cast it to Object array. Once its casted then we can get individual POJO classes. Only we need is to cast as per the sequence of the POJO class. Please find the below code.

List mainMenu = daoIntf.getMenu();

logger.debug("List size "+mainMenu.size());

logger.debug("lsit : "+mainMenu.get(0));

Iterator itr=mainMenu.iterator();

while(itr.hasNext()){

Object[] str=(Object[])itr.next();

logger.debug("str.length :"+str.length);

//menu=(Menu)str[0];

subMenuRole=(SubMenuRole)str[0];

subMenu=(SubMenu)str[1];

logger.debug("Menu Name : " +subMenu.getMenu().getName()+ " SubMenu : "+subMenu.getName()+" Role : "+subMenuRole.getRole().getName());

}

We are setting the list in the session as we have got from the DAO class. In this list there are 2 POJO classes so we need to iterate and show it in the front end.

menu.jsp

In the below jsp, please note the <s:iterator> tag is iterating the list which we have set in the session and we have given the list name during iteration is "usermenu". Once we have iterated the list then you can point to the pojo class by using the list name "usermenu[i]" where i is the sequence of pojo class which we have used to iterate the list in the java coding above.

<%@ taglib prefix="s" uri="/struts-tags"%>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<html>

<head>

</head>

<body>

<s:iterator value="%{#session.mainMenuList}" var="usermenu"

status="user">

<s:if test="#user.first == true">

<c:set var="menuElement" scope="page">

<s:property value="#usermenu[0].name" />

</c:set>

<h3 class="menuheader expandable">${menuElement}</h3>

</s:if>

<c:set var="currentMenuElement" scope="page">

<s:property value="#usermenu[0].name" />

</c:set>

<c:choose>

<c:when test="${currentMenuElement==menuElement}">

<li>

</li>

</c:when>

<c:otherwise>

</ul>

<c:set var="menuElement" scope="page">

<s:property value="#usermenu[0].name" />

</c:set>

<h3 class="menuheader expandable">${menuElement}</h3>

<c:if test="${currentMenuElement==menuElement}">

<li>

</li>

</c:if>

</c:otherwise>

</c:choose>

<s:if test="#user.last == true">

</ul>

</s:if>

</s:iterator>

</div>

</body>

</html>

Hope this code helps some of the developers.

Difference between Comparable and Comparator interface and usage

2012-06-12T14:09:00.001+05:30

Comparable interface provide compareTo method which can be used to do sorting in natural order but the Comparator interface provide the method compare which takes two arguments which can be used to sort based on more than one parameter.

For instance I have created a class UserDetails and comparing via Comparable interface and Comparator interface. Using comparator interface I am comparing the fname, in case the fname is equal then the sorting is done based on lName.

------------------------------------------------------------------------

public class UserDetails implements Comparable {

String fName;

String lName;

public UserDetails(String fName, String lName) {

super();

this.fName = fName;

this.lName = lName;

}

public String getfName() {

return fName;

}

public void setfName(String fName) {

this.fName = fName;

}

public String getlName() {

return lName;

}

public void setlName(String lName) {

this.lName = lName;

}

@Override

public int compareTo(Object o) {

// System.out.println("inside compareTo");

return getfName().compareTo(((UserDetails) o).getfName());

}

public String toString() {

return fName + " : " + lName;

}

------------------------------------------------------------------------

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

public class NameComparator implements Comparator {

// this comparator compares the first name and if its same it compares with

// the last name and gives the output

@Override

public int compare(Object o1, Object o2) {

UserDetails userDetails1 = (UserDetails) o1;

UserDetails userDetails2 = (UserDetails) o2;

if (userDetails1.getfName().equals(userDetails1.getfName())) {

return userDetails1.getlName().compareTo(userDetails1.getlName());

}else {

return userDetails1.getfName().compareTo(userDetails1.getfName());

}

public static void main(String args[]) {

List<UserDetails> userList = new ArrayList<UserDetails>();

userList.add(new UserDetails("Prajith", "k"));

userList.add(new UserDetails("Prajith", "a"));

userList.add(new UserDetails("Prajith", "A"));

userList.add(new UserDetails("Chandan", "urs"));

userList.add(new UserDetails("Gayatri", "c"));

userList.add(new UserDetails("Geeta", "P"));

userList.add(new UserDetails("Ajay", "kumar"));

userList.add(new UserDetails("Beena", "P"));

userList.add(new UserDetails("Akita", "D"));

*Comparing using the comparator interface implementation

* In assending order of the fname and lname,

Collections.sort(userList, new NameComparator());

System.out.println("Name Comparator output : " + userList);

// In desending order of the fname and lname

Collections.sort(userList, Collections.reverseOrder(new NameComparator()));

System.out.println("Name Comparator output in decending order : "

+ userList);

*Comparing using the Comparable interface implementation

* In assending order of the fname

Collections.sort(userList);

System.out.println("Name Comparator output using Comparable interface : " + userList);

// In desending order of the fname

Collections.sort(userList, Collections.reverseOrder());

System.out.println("Name Comparator output using Comparable interface in decending order : "+ userList);

}

------------------------------------------------------------------------

Output of the above program is as below.

------------------------------------------------------------------------

Name Comparator output : [Prajith : k, Prajith : a, Prajith : A, Chandan : urs, Gayatri : c, Geeta : P, Ajay : kumar, Beena : P, Akita : D]

Name Comparator output in decending order : [Prajith : k, Prajith : a, Prajith : A, Chandan : urs, Gayatri : c, Geeta : P, Ajay : kumar, Beena : P, Akita : D]

Name Comparator output using Comparable interface : [Ajay : kumar, Akita : D, Beena : P, Chandan : urs, Gayatri : c, Geeta : P, Prajith : k, Prajith : a, Prajith : A]

Name Comparator output using Comparable interface in decending order : [Prajith : k, Prajith : a, Prajith : A, Geeta : P, Gayatri : c, Chandan : urs, Beena : P, Akita : D, Ajay : kumar]

------------------------------------------------------------------------

Java Collections

2012-06-05T21:28:00.001+05:30

Collection: Java collection is simply an object that groups multiple elements into a single unit. Collections are used to store, retrieve, manipulate, and communicate aggregate data.

Benefits of Java Collection framework:

1. Reduces programming efforts.

2. Increase programming speed and quality.
3. Reduces efforts to design new APIs.
4. Standard collections interface are reusable.

Interfaces:

===========================================================
Collection Interface :
This interface is root of collection hierarchy. Java platform does't provide any direct implementation of the this interface but provides implementations of more specific subinterfaces, such as Set, List and Queue. Collection interface is generic. A Collection represents group of objects, known as its elements.

Interface declaration :
public interface Collection<E> extends Iterable<E>

Known Exception : UnsupportedOperationException
===========================================================
Set Interface :
This interface implements Collections interface. In this type of collections no duplicate values are allowed.

Interface declaration :
public interface Set <E> extends Collection <E>

Features :
1. Set does not allow duplicate elements.
2. Set contains at most one null element.
3. Set is unordered collection.
4. Set does not allow positional access.

Known Exception :NullPointerException or ClassCastException
----------------------------------------------------------------------------------------------------------
General purpose Implementation classes of Set Interface are :
1. HashSet :
This class implements the Set interface backed by Hash table.
Class declaration :
public class HastSet <E> extends AbstractSet <E>
implements Set <E>, Cloneable, Serializable
Features :

1. HashSet does not allow duplicate elements.

2. HashSet contains at most one null element.

3. HashSet is unordered collection.

4. HashSet does not allow positional access.

5. Unsychronized collection set.

HashSet can be converted into a synchronized collection.

ex.

Set s = Collections.synchronizedSet(new HashSet(.........));

----------------------------------------------------------------------------------------------------------

2. LinkedHashSet :

This class implements the Set interface and extends to HashSet. It maintains the order in which the elements were inserted in this set.

Class declaration :

public class LinkedHashSet <E> extends HashSet <E>

implements Set <E>, Cloneable, Serializable

Features :

It carries all the features of HashSet except the ordering of collection maintained by the LinkedHashSet is the order in which the elements were inserted into it.

HashSet can be converted into a synchronized collection.

ex.

Set s = Collections.synchronizedSet(new LinkedHashSet(.........));

===========================================================

SortedSet interface :

This interface extends to set interface. This set guarantees that its iterator will traverse the set in ascending element order, sorted according to the natural ordering of its elements.

Class declaration :

public class SortedSet <E> extends Set <E>

Features :

1. Ordered collection set.

2. Does not allow duplicate elements.

3. All element inserted into an sorted set must implement Comparable interface.

----------------------------------------------------------------------------------------------------------

General purpose Implementation classes of SortedSet Interface are :

1. TreeSet :

This set implements SortedSet interface.

Class declaration :

public class TreeSet <E> extends AbstractSet <E>

implements SortedSet <E>, Cloneable, Serializable

Features :

Carries all the features of the SortedSet interface and this class is unsynchronized.

Can be converted to synchronized collection.

ex.

SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));

===========================================================
List Interface :
This interface implements Collections interface. An ordered Collection also known as sequence.

Interface declaration :

public interface List <E> extends Collection <E>

Features :

1. List allows duplicate elements.

2. List contains null elements.

3. List is a ordered collection.

4. Allows positional access.

5.List interface provides specialized Iterator called ListIterator that allows insertion, replacement and bidirectional access in addition to the normal operations that the iterator interface provides.

Known Exception :NullPointerException or ClassCastException

----------------------------------------------------------------------------------------------------------

General purpose Implementation classes of SortedSet Interface are :

1. ArrayList :

This ArrayList implements List interface.

Class declaration :

public class ArrayList <E> extends AbstractList <E>

implements List <E>, RandomAccess, Cloneable, Serializable

Features :

1. Resizable-array implementation of the List interface.

2. Permits duplicate elements.

3. Both LinkedList and the ArrayList maintain the order in which the elements are inserted.

4. Roughly equivalent to Vector except that it is unsynchronized.

5.The iterators returned by this class's iterator and listIterator methods are fail-fast.

Can be converted to synchronized collection.

ex.

List list = Collections.synchronizedList(new ArrayList(...));
----------------------------------------------------------------------------------------------------------
2. LinkedList :
Doubly-linked list implementation of List interface. In addition to implementing the List interface the linkedList class provides uniformly named methods to get, remove and insert element at the beginning and end of the list. These operations allow linked lists to be use as a stack, queue, or double-ended queue(deque).Provide better performance if the elements are frequently inserted or deleted within the list. Also implements Queue interface. When accessed via the queue interface, LinkedList behaves as FIFO (First In First Out) Queue.

Class declaration :

public class LinkedList <E> extends AbstractSequentialList <E>

implements List <E>, Queue <E>, Cloneable, Serializable




Features :

1. Resizable-array implementation of the List interface.

2. Permits duplicate elements.

3. Both LinkedList and the ArrayList maintain the order in which the elements are inserted.

4. All of the operations perform as could be expected for a doubly-linked
 list

5. Unsynchronized list.




Can be converted to synchronized collection.

ex.


List list = Collections.synchronizedList(new LinkedList(...));

===========================================================
Map interface :
An object which maps keys to value. A map can not contain duplicate values and each key can map to only one value.

Class declaration :

public interface Map <K,V>

Features :

1. Object maps key and value.

2. Map cannot contain duplicate key.

3. Each key can map at most one value.

4. Map at most contain one null key value.

5. Unordered collection.

Exception : NullPointerException, ClassCastException or UnsupportedOpertionException

----------------------------------------------------------------------------------------------------------


General purpose Implementation classes of Map Interface are :




1. HashMap :




Hash table based implementation of the Map interface.




Class declaration :

public class HashMap <K,V> extends AbstractMap <K,V>

implements Map <K,V>, Cloneable, Serializable




Features : 



1. Unsynchronized map.

2. Unordered map.

3. Allows null key and value at most one.

4. HashMap is roughly equivalent to the Hash table except that it is unsynchronized and allows null.




HashMap can be converted into a synchronized map. 

ex.





Map m = Collections.synchronizedMap(new HashMap(...));
----------------------------------------------------------------------------------------------------------


2. LinkedHashMap :


Hash table and linked list implementation of the Map interface,
 with predictable iteration order. This implementation differs from HashMap in that it maintains a doubly-linked list running through
 all of its entries.  This linked list defines the iteration ordering,
 which is normally the order in which keys were inserted into the map
 (insertion-order).  Note that insertion order is not affected
 if a key is re-inserted into the map.



Class declaration :

public class LinkedHashMap <K,V> extends HashMap <K,V>

implements Map <K,V>




Features : 



1. Unsynchronized map.

2. Maintain the insertion order.






LinkedHashMap can be converted into a synchronized map. 

ex.





Map m = Collections.synchronizedMap(new LinkedHashMap(...));
===========================================================


SortedMap interface : 


A map whose mapping are automatically sorted by key, either in keys natural ordering by a compartor provided when a sortedMap instance is created. It extends Map interface.



Interface declaration :

public interface SortedMap <K,V> extends Map <K,V>



Features :

1. Sorted Key in ascending.

2. EntrySet, KeySet for iterating over map


----------------------------------------------------------------------------------------------------------
General purpose Implementation classes of SortedMap Interface is :


TreeMap :


Implementation of SortedMap interface.



Class declaration :

public class TreeMap <K,V> extends AbstractMap <K,V>

implements SortedMap <K,V>, Cloneable, Serializable




Features : 



1. ascending key order.

2. Iterator are fail-safe.


===========================================================


Legacy Implementations - Older collection classes have
been retrofitted to implement the collection interfaces.


Vector :
Synchronized resizable-array implementation of the List interface
with additional "legacy methods." 


 



Class declaration :

public class Vector <E> extends AbstractList <E>

implements List <E>, RandomAccess, Cloneable, Serializable




Features : 



1. Synchronized resizable array implementation od List interface with additional Legacy methods.

2. Size of vector can grow or shrink as the needed to accommodate adding and removing items after the vector has been created.


----------------------------------------------------------------------------------------------------------


Hashtable :
Synchronized hash table implementation of the Map interface
that does not allow null keys or values, with additional
"legacy methods."


Class declaration :
public class Hashtable <K,V> extends Dictionary <K,V> 
implements Map<K,V>, Cloneable , Serializable


Features:
1. Synchronized Map.
2. Does not allow null values for key and value.
===========================================================


Difference between HashMap & HashTable



1. HashTable is synchronized while HashMap is't.
2. Iterator in HashMap is fail-safe while enumerator in Hashtable is't.
3. HashMap permits null value in it but Hashtable does't.



Difference between ArrayList & LinkedList


1. ArrayList can Random access elements in the list so its faster while accessing, even though the LinkedList has the method get(int index), the LinkedList has to iterate over the list to get the index value so its slower as compared to ArrayList while doing random access.
2. LinkedList is faster while doing the delete and add operations than ArrayList.



Reference of the Collection

CustomValidation using Annotation in Struts

2012-05-25T16:43:00.002+05:30

While doing the validation, the developer can write his own custom validation to validate the fields. In Struts2 it can be done by using @CustomValidator. The Custom Validator takes mandatory fields as:
1. type - it is the name to the validator which will be defined in the validation.xml
2. message - it is the message which you would like to show on the validation failure.
3.fieldName - this will be necessary if you are not defining the validator above the field name. In the below example i have used the validator at the class level so its necessary to mention the name of the validator.

A custom validator can be implemented by implementing the FieldValidatorSupport or the ValidatorSupport. Below is the example to write a custom validator.

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PhoneNumberValidator.java :
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package com.lntinfotech.office.common;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import com.opensymphony.xwork2.validator.ValidationException;

import com.opensymphony.xwork2.validator.validators.FieldValidatorSupport;

public class PhoneNumberFieldValidator extends FieldValidatorSupport {

private Logger logger=LoggerFactory.getLogger(getClass());

public void validate(Object object) throws ValidationException {

String fieldName = getFieldName();

Object value = this.getFieldValue(fieldName, object);

if (!(value instanceof String)) {

return;

}

String str = ((String) value).trim();

try{

if (str.length() != 0) {

if (str.indexOf("-", 0) <= 5) {

if (str.indexOf("-") == str.lastIndexOf("-")) {

String stdcode = str.substring(0, str.indexOf("-"));

String phoneNo = str.substring((str.indexOf("-") + 1));

if(phoneNo.length()<6){

addFieldError(fieldName, object);

}

try {

Integer.parseInt(stdcode);

Integer.parseInt(phoneNo);

} catch (NumberFormatException nfe) {

addFieldError(fieldName, object);

logger.error("<-- validate(Object object) :"+nfe);

return;

}

return;

}

}catch(Exception e ){

addFieldError(fieldName, object);

logger.error("<-- validate(Object object) :"+e);

return;

}

note:

The fieldName and getFieldValue are implemented in superclass and are used to retrieve the name and value of the field getting validated respectively.
The addFieldError method is used to add any failed validations to the list of error to be displayed.
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The validators.xml is used to map the validator class with a name which will be used in the class which will request validation.
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validators.xml
-----------------------------------------------------------------------

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE validators PUBLIC

"-//OpenSymphony Group//XWork Validator Config 1.0//EN"

"http://www.opensymphony.com/xwork/xwork-validator-config-1.0.dtd">

</validators>

-----------------------------------------------------------------------

In the below class we will be validating the phone number using the custom validator. I have removed various other fields from the class as its not necessary. For validating the field either you can define the validation at the class level as I have done below or can be done on the getter method of the field. for doing the validation at the getter method you need to define the validator just above the getter method.

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RegistrationAction.java
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package com.lntinfotech.office.controller;

import org.apache.struts2.convention.annotation.Action;

import org.apache.struts2.convention.annotation.InterceptorRef;

import org.apache.struts2.convention.annotation.ParentPackage;

import org.apache.struts2.convention.annotation.Result;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import com.opensymphony.xwork2.ActionSupport;

import com.opensymphony.xwork2.validator.annotations.CustomValidator;

import com.opensymphony.xwork2.validator.annotations.Validations;

@ParentPackage(value = "office")

@InterceptorRef("jsonValidationWorkflowStack")

@Validations(

customValidators = { @CustomValidator(fieldName = "phoneNo", message = "Please enter the phone number in STD-Phone(XXX-XXXXXX) Format", type = "phoneNumberFieldValidator") })

public class RegistrationAction extends ActionSupport {

private static final long serialVersionUID = 1L;

private Logger logger = LoggerFactory.getLogger(getClass());

private String phoneNo;

public String getPhoneNo() {

return phoneNo;

}

public void setPhoneNo(String phoneNo) {

this.phoneNo = phoneNo;

}

@Action(value = "/createuser", results = {

@Result(location = "registrationSuccess.jsp", name = "success"),

@Result(location = "registration.jsp", name = "input"),

@Result(location = "registration.jsp", name = "error") }, className = "registerUser")

public String createUser() {

logger.debug("--> createUser()");

return "success";

}

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Struts 2.3.3 integration with Spring 3.0.5 using Struts annotation

2012-05-17T01:20:00.000+05:30

An example application to integrate Struts and Spring using the struts annotation. The application is very simple, just shown the way to do the confuguration and hence not implemented variuos features given by the two framework.

First we will do the configuration in the Deployment discriptor to use Struts FilterDispatcher and the spring WebApplicationContext. Below is the web.xml

------------------------------------------------------------------------------------
web.xml
------------------------------------------------------------------------------------

<?xml version="1.0" encoding="UTF-8"?>

<web-app id="starter" version="2.4"

xmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<display-name>Struts 2 - Maven Archetype - Starter</display-name>

<context-param>

<param-name>contextConfigLocation</param-name>

<param-value>classpath*:applicationContext*.xml</param-value>

</context-param>

<filter-name>action2-cleanup</filter-name>

<filter-class>org.apache.struts2.dispatcher.ActionContextCleanUp</filter-class>

</filter>

<filter-name>action2</filter-name>

<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>

</filter>

<filter-mapping>

<filter-name>action2-cleanup</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

<filter-mapping>

<filter-name>action2</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

</listener>

<servlet-name>jspSupportServlet</servlet-name>

<servlet-class>org.apache.struts2.views.JspSupportServlet</servlet-class>

<load-on-startup>5</load-on-startup>

</servlet>

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

<welcome-file>default.jsp</welcome-file>

<welcome-file>index.html</welcome-file>

</welcome-file-list>

</web-app>

------------------------------------------------------------------------------------
now we will define the struts.xml for the basic configuration. This can be moved as per your requirment.
------------------------------------------------------------------------------------
struts.xml
------------------------------------------------------------------------------------

<!DOCTYPE struts PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

"http://struts.apache.org/dtds/struts-2.3.dtd">

<package name="showcase" extends="struts-default,json-default"

namespace="/">

</package>

</struts>

------------------------------------------------------------------------------------
Now we will configure the spring webapplicationcontext so that we can integrate the spring with the struts.xml
------------------------------------------------------------------------------------
applicationContext.xml
------------------------------------------------------------------------------------

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE beans PUBLIC

"-//SPRING//DTD BEAN//EN"

"http://www.springframework.org/dtd/spring-beans.dtd">

</bean>

</beans>

------------------------------------------------------------------------------------

Now we will configure the struts mapping using the annotation in the class file. In the below java class we have annotated the method. The annotation "Action" has been used which tells the application that for which url mapping which method or class has to be executed . In the below class we have defined the Action value as "helloworld", so when the url "/helloworld.action" will be hit the application knows which method it has to execute. We have also defined few more attributes. I mean results, which tells the application once it has executed the class as per the definition which view it has to redirect the control. The last configuration "className" is too important in the StrutsSpring application, As this attribute tells the application to look into the applicationContext of the spring for the particular bean definition defined.

Please note as our application is started the url "/helloworld.action" will be hit, so as per the configuration we have done the control will be coming to the HelloWorldAction.java. Once the control comes here the other configuration plays their part. The configuration "className" done above the method hello() tells the application to look for the name helloworld in the applicationcontext.xml.(the attribute "className" need not be same as url. you can give the same name you will define in the applicationContext.xml). Once the bean definition is seen the control moves to the class defined as per the applicationContext.xml. In our application the control moves to the Testing.java and executes the method hello(). This is because we have defined the configuration above the hello() method in the HelloWorldAction.java.(The controller takes the name of the method above which the configuration is defined and search and execute the same name method in the class defined by the spring bean).

Now if you dont want your spring configuration to overwrite the method defined by the struts, you just hace to remove the configuration "className". In that case the application will execute the method above which the mapping configuration has been defined. In our application that would be hello() method from the HelloWorldAction.java.
------------------------------------------------------------------------------------
HelloWorldAction .java
------------------------------------------------------------------------------------
package com.lnt.struts;

import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.ParentPackage;
import org.apache.struts2.convention.annotation.Result;

import com.opensymphony.xwork2.ActionSupport;

@ParentPackage(value = "showcase")

public class HelloWorldAction extends ActionSupport {

@Action(value="helloworld",results={@Result(location="hello.jsp",name="success"),@Result(location="input.jsp",name="input"),@Result(location="error.jsp",name="error")},className="helloworld")
public String hello(){
System.out.println("inside Helloworld hello");
return "error";
}

   public String execute() throws Exception {
   System.out.println("inside execute method");
   return SUCCESS;
   }
}
------------------------------------------------------------------------------------
Testing.java
------------------------------------------------------------------------------------
package com.lnt.struts;
public class Testing {
public String hello(){
  System.out.println("inside Testing hello");
  return "error";
}

public String execute() throws Exception {
         System.out.println("inside Testing execute method");
     return "success";
     }
}
------------------------------------------------------------------------------------

Now you may be wondering why other methods are been defined if its not used any where...... It is just to let you know how to define the same configuration for a class. For example

@ParentPackage(value = "showcase")
@Action(value="helloworld",results={@Result(location="hello.jsp",name="success"),@Result(location="input.jsp",name="input"),@Result(location="error.jsp",name="error")},className="helloworld")
public class HelloWorldAction extends ActionSupport {
// same code as above except the configuration above the method.
}

When you are defining configuration for the class the same configuration you need to put above the class declaration. Now the application will act the same way it has done for the method but instead of executing the hello() method defined in the class it will execute the execute() method of the class. This is because we have exetended our class to ActionSupport. Now as per the configuration of the "className", the application will decide which method to execute from which class the same way it does for the method configuration.
------------------------------------------------------------------------------------
error.jsp
------------------------------------------------------------------------------------

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

error

</body>

</html>

------------------------------------------------------------------------------------
input.jsp
------------------------------------------------------------------------------------

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

input

</body>

</html>

------------------------------------------------------------------------------------
hello.jsp
------------------------------------------------------------------------------------

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

Hello

</body>

</html>

------------------------------------------------------------------------------------
index.jsp
------------------------------------------------------------------------------------

<% response.sendRedirect("helloworld.action"); %>

the index.jsp can be avoided by configuring the welcome tag in the web.xml to directly pointing helloworld.action url.
------------------------------------------------------------------------------------
Project Sturcture
------------------------------------------------------------------------------------

------------------------------------------------------------------------------------
library required
------------------------------------------------------------------------------------
this jar list is for various other needs. Whole jars may not be needed for this application

antlr-2.7.6.jar
aopalliance-1.0.jar
asm-3.3.jar
asm-commons-3.3.jar
asm-tree-3.3.jar
c3p0-0.9.1.jar
commons-collections-3.1.jar
commons-fileupload-1.1.1.jar
commons-io-2.0.1.jar
commons-lang3-3.1.jar
commons-logging-1.0.4.jar
dom4j-1.6.1.jar
dwr-1.1-beta-3.jar
freemarker-2.3.19.jar
hibernate-c3p0-3.6.3.Final.jar
hibernate-commons-annotations-3.2.0.Final.jar
hibernate-core-3.6.3.Final.jar
hibernate-jpa-2.0-api-1.0.0.Final.jar
javassist-3.11.0.GA.jar
jta-1.1.jar
log4j-1.2.16.jar
mysql-connector-java-5.1.9.jar
ognl-3.0.5.jar
sitemesh-2.4.2.jar
slf4j-api-1.6.4.jar
slf4j-jcl-1.6.4.jar
slf4j-log4j12-1.6.4.jar
spring-2.5.6.jar
spring-aop-3.0.5.RELEASE.jar
spring-asm-3.0.5.RELEASE.jar
spring-beans-3.0.5.RELEASE.jar
spring-context-3.0.5.RELEASE.jar
spring-core-3.0.5.RELEASE.jar
spring-expression-3.0.5.RELEASE.jar
spring-web-3.0.5.RELEASE.jar
struts2-config-browser-plugin-2.3.3.jar
struts2-convention-plugin-2.3.3.jar
struts2-core-2.3.3.jar
struts2-sitemesh-plugin-2.3.3.jar
struts2-spring-plugin-2.3.3.jar
xwork-core-2.3.3.jar

------------------------------------------------------------------------------------

pom.xml configuration for the above project:

------------------------------------------------------------------------------------

this pom.xml is configured to use Struts 2.3.3 , Spring 3.0.5 , Hibernate 3.6.3 and mysql 5.1

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

<artifactId>struts</artifactId>

<name>StrutsSpringproject</name>

<version>1.0.0-BUILD-SNAPSHOT</version>

<struts2.version>2.3.3</struts2.version>

</properties>

<groupId>junit</groupId>

<artifactId>junit</artifactId>

</dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-core</artifactId>

<version>${struts2.version}</version>

</dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-sitemesh-plugin</artifactId>

<version>${struts2.version}</version>

</dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-spring-plugin</artifactId>

<version>${struts2.version}</version>

</dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-config-browser-plugin</artifactId>

<version>${struts2.version}</version>

</dependency>

<groupId>org.apache.struts</groupId>

<artifactId>struts2-convention-plugin</artifactId>

<version>${struts2.version}</version>

</dependency>

<groupId>javax.servlet</groupId>

<artifactId>servlet-api</artifactId>

<scope>provided</scope>

</dependency>

<groupId>javax.servlet</groupId>

<scope>provided</scope>

</dependency>

<groupId>commons-fileupload</groupId>

<artifactId>commons-fileupload</artifactId>

</dependency>

<groupId>uk.ltd.getahead</groupId>

</dependency>

<groupId>org.hibernate</groupId>

<artifactId>hibernate-core</artifactId>

<version>3.6.3.Final</version>

</dependency>

<groupId>org.hibernate</groupId>

<artifactId>hibernate-c3p0</artifactId>

<version>3.6.3.Final</version>

</dependency>

</dependency>

</dependency>

</dependency>

<groupId>org.springframework</groupId>

<artifactId>spring</artifactId>

</dependency>

<groupId>mysql</groupId>

<artifactId>mysql-connector-java</artifactId>

</dependency>

<!-- <dependency> <groupId>com.jgeppert.struts2.jquery</groupId> <artifactId>struts2-jquery-plugin</artifactId>

<version>3.3.1</version> </dependency> <dependency> <groupId>com.jgeppert.struts2.jquery</groupId>

<artifactId>struts2-jquery-grid-plugin</artifactId> <version>3.3.1</version>

</dependency> <dependency> <groupId>com.jgeppert.struts2.jquery</groupId>

<artifactId>struts2-jquery-richtext-plugin</artifactId> <version>3.3.1</version>

</dependency> <dependency> <groupId>com.jgeppert.struts2.jquery</groupId>

<artifactId>struts2-jquery-tree-plugin</artifactId> <version>3.3.1</version>

</dependency> <dependency> <groupId>com.jgeppert.struts2.jquery</groupId>

<artifactId>struts2-jquery-mobile-plugin</artifactId> <version>3.3.1</version>

</dependency> -->

</dependencies>

<build>

<artifactId>maven-eclipse-plugin</artifactId>

<projectnature>org.springframework.ide.eclipse.core.springnature</projectnature>

</additionalProjectnatures>

<buildcommand>org.springframework.ide.eclipse.core.springbuilder</buildcommand>

</additionalBuildcommands>

</configuration>

</plugin>

<groupId>org.apache.maven.plugins</groupId>

<artifactId>maven-compiler-plugin</artifactId>

<compilerArgument>-Xlint:all</compilerArgument>

</configuration>

</plugin>

<groupId>org.codehaus.mojo</groupId>

<artifactId>exec-maven-plugin</artifactId>

</configuration>

</plugin>

</plugins>

</build>

</project>

------------------------------------------------------------------------------------

project structure as a maven project

------------------------------------------------------------------------------------

Configure HTTPS in local server(Tomcat)

2012-04-30T17:52:00.000+05:30

The below instructions explain how to configure Tomcat for SSL/TLS. After following below instructions, users may access web applications securely through port 8443.

The instructions show how to generate a self-signed certificate that browsers can use to authenticate the server. Consequently, browsers will not be able verify the authenticity of the certificate because it will not have been signed by a trusted third party whose certificates are pre-installed in the client system or added to the client system but still you can use HTTPS without doing any of the above procedures, but your users will need to accept an un-trusted certificate each time they visit your site.

Create Keystore with Self-Signed Certificate

You need to generate a self-signed certificate and store it in a file called keystore under the conf folder within the Tomcat. To do this, run the keytool command as shown below, leaving the storepass and keypass values both equal to changeit. This command may take a long time to complete, so be patient. After generating the keystore file, move it into the conf folder.

To run the command, you need to be at an operating system command prompt. The keytool command is part of the Java SDK. If your system only contains the Java JRE, then you will need to install the JDK to get access to this command.

Running keytool under Windows

keytool -genkey ^
        -keystore keystore ^
        -alias tomcat ^
        -keyalg RSA ^
        -keysize 2048 ^
        -dname CN=localhost ^
        -storepass changeit ^
        -keypass changeit

If you get a message that the command is unknown, then you need to provide the
full pathname to the keytool executable 
(or add the bin folder in your jdk installation to the path variable in your environment).

The keystore file will be created at the level where you are running the above command. eg. if you are running the command from C:/ then search the file in c:/ itself. This file then you need to copy inside the tomcat conf folder.


Running keytool under Linux and Mac OS X
keytool -genkey \
        -keystore keystore \
        -alias tomcat \
        -keyalg RSA \
        -keysize 2048 \
        -dname CN=localhost \
        -storepass changeit \
        -keypass changeit
The CN variable in the certificate should contain the domain name of your server.Because you are running Tomcat and your browser from the same machine,setting theCN variable to localhost as done above is OK.However, if you wanted to access Tomcat from a remote machine, you would need to replace localhost with the domain name of the machine on which Tomcat is running.

Once you have moved the file keystore under the apache-tomcat-7.0.23/conf folder then you need to modify the server.xml file under the apache-tomcat-7.0.23/conf folder. Now edit the file and uncomment the Connector element with the port 8443. for your connivence i am pasting the commented code in my server.xml file which you need to uncomment it.

   <!--
    <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true"
               maxThreads="150" scheme="https" secure="true"
               clientAuth="false" sslProtocol="TLS" />
    -->

then add the below attribute to the above element

keystoreFile="conf/keystore"

The following is an example Connector element that sets up HTTPS on port 8443.


<Connector port="8443"
           maxThreads="200" 
           minSpareThreads="5" 
           maxSpareThreads="75"
           enableLookups="true" 
           disableUploadTimeout="true"
           acceptCount="100"
           scheme="https"
           secure="true"
           SSLEnabled="true"
           clientAuth="false"
           sslProtocol="TLS"
           keystorePass="changeit"
           keystoreFile="conf/keystore" />

If you are running Windows Vista, regular users may not have the privileges to modify server.xml. In this case, you need to edit server.xml as adminstrator. To do this, right click on wordpad in the Windows start menu and select run as adminstrator.

once you are done the above procedure then you need to run your application and test it using 8443 port.

https://localhost:8443/<ServletContest>

A Simple News Feed Application

2012-04-30T12:51:00.000+05:30

We will be using RSS for achieving the simple news feed application. People interpret the acronym RSS in several ways. For example, you may hear that RSS stands for Rich Site Summary, or Really Simple Syndication, or even RDF Site Summary. Most people simply refer to the technology as RSS. RSS is an XML-based format that allows the syndication of lists of hyperlinks, along with other information, or metadata, that helps viewers decide whether they want to follow the link.

RSS allows peoples’ computers to fetch and understand the information, so that all of the lists they’re interested in can be tracked and personalized for them. It is a format that’s intended for use by computers on behalf of people, rather than being directly presented to them (like HTML). To enable this, a Web site will make a feed, or channel, available, just like any other file or resource on the server. Once a feed is available, computers can regularly fetch the file to get the most recent items on the list.

FEED

A feed contains a list of items or entries, each of which is identified by a link. Each item can have any amount of other metadata associated with it as well. A simple example of feed

<item>
  <title>test</title>
  <link>any site which provide data in RSS</link>
  <description>description goes here</description>
</item>

---------------------------------------------------------------

Flow of information for RSS

---------------------------------------------------------------

---------------------------------------------------------------

Create the simple news feed application

-----------------------------------------

Create a simple dynamic web project using the eclipse. Now create a new servlet by name RSSServlet

RSSServlet

package com.lnt.web;
 
import java.io.IOException;
import java.net.URL;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.sun.syndication.feed.synd.SyndFeed;
import com.sun.syndication.io.FeedException;
import com.sun.syndication.io.SyndFeedInput;
import com.sun.syndication.io.XmlReader;

public class RSSServlet extends HttpServlet {

 private Logger logger = Logger.getLogger(this.getClass());
 private RequestDispatcher homeJsp;
 
 @Override
 public void init(ServletConfig config) throws ServletException {
  ServletContext context = config.getServletContext();
  homeJsp = context.getRequestDispatcher("/WEB-INF/jsp/home.jsp");
 }

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  logger.debug("Retrieving yahoo news feed");
  URL url = new URL("http://rss.news.yahoo.com/rss/tech");
  SyndFeedInput syndFeedInput = new SyndFeedInput();
  SyndFeed syndFeed = null;
  XmlReader xmlReader = new XmlReader(url);
  try {
   syndFeed = syndFeedInput.build(xmlReader);
  } catch (IllegalArgumentException e) {
   logger.error("", e);
  } catch (FeedException e) {
   logger.error("", e);
  }
  logger.debug("Forwarding to home.jsp");
  req.setAttribute("syndFeed", syndFeed);
  homeJsp.forward(req, resp);
 }
}

you need to add the below mentioned library to your project.

1. jdom-1.1.3.jar

2. log4j-1.2.14.jar

3. rome-1.0.jar

---------------------------------------------------------------

Create a jsp inside the WEB-INF/jsp folder of the project.

home.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<%@ page import="com.sun.syndication.feed.synd.SyndFeed" %>

<%@ page import="com.sun.syndication.feed.synd.SyndEntry" %>

<%@ page import="java.util.Iterator" %>

<jsp:useBean id="syndFeed" scope="request" type="SyndFeed" />

<html>

<head>

<title>website</title>

</head>

<body>

<ul>

Iterator it = syndFeed.getEntries().iterator();

while (it.hasNext())

{

SyndEntry entry = (SyndEntry) it.next();

<li>

</li>

<% } %>

</ul>

</body>

</html>

Some times the above jsp may show error as undefined type Syndfeed, please ignore the same.

In the deployment Descriptor add the mapping as below.

---------------------------------------------------------------

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

<display-name>RSStest</display-name>

<servlet-name>home</servlet-name>

<servlet-class>com.lnt.web.RSSServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>home</servlet-name>

<url-pattern>/home</url-pattern>

</servlet-mapping>

</web-app>

---------------------------------------------------------------

Required library

1. jdom-1.1.3.jar

2. log4j-1.2.14.jar

3. rome-1.0.jar

---------------------------------------------------------------

now run the project you should be able to see the news links in your page.

Spring hibernate integration

2012-04-23T18:42:00.004+05:30

In Spring the hibernate integration becomes easy and you need not to create separate hibernate.cfg.xml for the project. You can configure the hibernate settings in the spring web application context itself. Please find the simple project using the spring hibernate configuration.

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"

id="WebApp_ID" version="3.0">

<display-name>CaptionContest</display-name>

<welcome-file-list>

<welcome-file>/home.html</welcome-file>

</welcome-file-list>

<servlet-name>SpringHibernate</servlet-name>

<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>SpringHibernate</servlet-name>

<url-pattern>*.html</url-pattern>

</servlet-mapping>

<session-config>

<session-timeout>30</session-timeout>

</session-config>

</web-app>

----------------------------------------------------------------------------

SpringHibernate-servlet.xml

Please replace your username, password and database name of the database in the below file in the respective positions.

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dwr="http://www.directwebremoting.org/schema/spring-dwr"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-2.5.xsd

http://www.directwebremoting.org/schema/spring-dwr

http://www.directwebremoting.org/schema/spring-dwr-3.0.xsd">

<bean id="viewResolver"

class="org.springframework.web.servlet.view.InternalResourceViewResolver">

<property name="viewClass"

value="org.springframework.web.servlet.view.JstlView" />

</bean>

<bean id="myDataSource"

class="org.springframework.jdbc.datasource.DriverManagerDataSource"

destroy-method="close">

</bean>

<bean id="mySessionFactory"

class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">

<list>

<value>com.lnt.spring.User</value>

</list>

</property>

<props>

<prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect</prop>

<prop key="hibernate.hbm2ddl.auto">validate</prop>

<prop key="hibernate.c3p0.testConnectionOnCheckout">false</prop>

</props>

</property>

</bean>

</bean>

</bean>

</beans>

-------------------------------------------------------------------------

TestController.java

package com.lnt.spring;

import java.util.List;

import java.util.ListIterator;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

public class TestController extends MultiActionController{

private User user;

private TestDAO testDAO;

public void setTestDAO(TestDAO testDAO) {

this.testDAO = testDAO;

}

public void setUser(User user) {

this.user = user;

}

public ModelAndView home(HttpServletRequest request,HttpServletResponse response) throws Exception{

List<User> list=testDAO.loginRequest("prajith", "prajith");

ListIterator<User> itr=list.listIterator();

System.out.println(list.get(0).getFname());

System.out.println("list size :"+list.size());

while(itr.hasNext()){

user=itr.next();

System.out.println("user fname :"+user.getFname());

}

return new ModelAndView("home","user",user.getFname());

}

------------------------------------------------------------------------------------------------------
TestDAO.java

package com.lnt.spring;

import java.util.List;

import org.hibernate.SessionFactory;

import org.springframework.orm.hibernate3.HibernateTemplate;

public class TestDAO {

private HibernateTemplate hibernateTemplate;

public void setSessionFactory(SessionFactory sessionFactory){

this.hibernateTemplate = new HibernateTemplate(sessionFactory);

}

public List<User> loginRequest(String userName, String password) throws Exception{

List<User> list=hibernateTemplate.find("from User u where u.username = ? and u.password=? ",new Object[] {userName,password});

System.out.println("list size :"+list.size());

return list;

}

-------------------------------------------------------------------------

User.java

package com.lnt.spring;

import java.io.Serializable;

import javax.persistence.*;

/**

* The persistent class for the user database table.

@Entity

public class User implements Serializable {

private static final long serialVersionUID = 1L;

@Id

@GeneratedValue(strategy=GenerationType.AUTO)

private int id;

private String fname;

private String password;

private String username;

public User() {

}

public int getId() {

return this.id;

}

public void setId(int id) {

this.id = id;

}

public String getFname() {

return this.fname;

}

public void setFname(String fname) {

this.fname = fname;

}

public String getPassword() {

return this.password;

}

public void setPassword(String password) {

this.password = password;

}

public String getUsername() {

return this.username;

}

public void setUsername(String username) {

this.username = username;

}

----------------------------------------------------------------------------------------------------

home.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

<h1>The user First Name "${user}" is coming form the database using spring hibernate</h1>

</body>

</html>

--------------------------------------------------------------------------

Please find the project structure of the project.

--------------------------------------------------------------------------

Please note the required jar list.

1. antlr-2.7.6.jar
2 .commons-collections-3.1.jar
3. commons-logging.jar
4. dom4j-1.6.1.jar
5. hibernate-jpa-2.0-api-1.0.0.Final.jar
6. hibernate3.jar
7. javassist-3.9.0.GA.jar
8. jcl-over-slf4j-1.6.4-sources.jar
9. jstl.jar
10. jta-1.1.jar
11. mysql-connector-java-5.1.18-bin.jar
12. slf4j-api-1.6.4.jar
13. slf4j-jcl-1.6.4.jar
14. slf4j-log4j12-1.6.4-sources.jar
15. spring-webmvc.jar
16. spring.jar
17. standard.jar

Properties file usage in Spring framework

2012-04-21T15:44:00.003+05:30

Create a property file with the required messages and keep the file under the project class path. below is a sample property file.

default-message.properties

menu.one=testing property file

report.mainmenu.one=Report one

report.mainmenu.two=Report two

report.mainmenu.three=Report three

report.mainmenu.four=Report four

report.mainmenu.five=Report five

---------------------------------------------------------------------------------

In your web application context xml specify the bean as below

</bean>

When ever you want to use the property value in the backend you can use the Spring injection and inject the property value to the class. Example as below.

</bean>

---------------------------------------------------------------------------------

Usage of the property value in the class. example as below.

ReportController.java

package com.lnt.rg.web;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.springframework.context.MessageSource;

import org.springframework.web.servlet.ModelAndView;

import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

import com.lnt.rg.common.Template;

public class ReportController extends MultiActionController {

protected final Log logger=LogFactory.getLog(getClass());

private Template template;

private MessageSource messages;

public void setMessages(MessageSource messages) {

this.messages = messages;

}

public void setTemplate(Template template) {

this.template = template;

}

public ModelAndView propertyFile(HttpServletRequest request, HttpServletResponse response){

if(messages!=null){

String str=messages.getMessage("menu.one", null, null);

System.out.println("str ::::"+str);

}else{

System.out.println("messageSourc is null");

}

return new ModelAndView("test");

}

As shown above the we can use the property value in backend(in java code).

------------------------------------------------------------------------------------

Getting the value from the property file to the frontend JSP. below is the code.

test.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

</body>

</html>

Displaytags1.2 integration with spring

2012-04-21T12:07:00.000+05:30

Below is an example to implement display tag in jsp.

-----------------------------------------------------------------------

<%@ taglib uri="http://displaytag.sf.net" prefix="display"%>

<html>

<head>

<title>All Cartoon</title>

</head>

<body>

<form method="post" action="<%=request.getContextPath() %>/publishCartoon.html">

<display:table uid="cartoon" export="true"

name="sessionScope.cartoonList" defaultsort="1"

defaultorder="ascending" pagesize="3"

requestURI="/prePublishCartoon.html">

<display:setProperty name="export.pdf" value="true" />

<display:caption>Cartoon Details</display:caption>

<display:column title="ID">

<input type="radio" name="id"

value="<c:out value="${cartoon.id}"/>"

<c:if test="${param.id == test.id and param.method != 'Save'}"></c:if>

style="margin: 0 0 0 4px" onclick="radio(this)" />

</display:column>

<display:column property="image_Name" title="Image Name" />

<display:column property="published" title="Published(Y/N)" />

<display:column property="publishDate" title="Published Date"

sortable="true" />

<display:column property="upload_Date" title="Upload Date"

sortable="true" />

<display:column property="user.fname" title="Artist" />

<display:column title="Cartoon" autolink="true">

<img src="<%=request.getContextPath() %>${cartoon.file_path}"

alt="image" height="145" width="145" />

</display:column>

</display:table>

<div>

</div>

</form>

</body>

</html>

Including the taglib is very important in the jsp. Without which the display tag wont work.
before redirecting your application to the above jsp it is mandatory to keep your list ready and pass to the jsp. You can pass the list via

pageScope
requestScope (default)
sessionScope
applicationScope

In the above example i have used sessionScope.

-----------------------------------------------------------------------------------------------------------------

To enable the export functionality add export="true" inside the tag <display:table>. Also create one property file named displaytag.properties and put the below content.

displaytag.properties

sort.amount=list

paging.banner.placement=top

export.types=csv excel xml pdf rtf

export.excel=true

export.csv=true

export.xml=true

export.pdf=true

export.rtf=true

export.excel.class=org.displaytag.export.excel.DefaultHssfExportView

export.pdf.class=org.displaytag.export.DefaultPdfExportView

export.rtf.class=org.displaytag.export.DefaultRtfExportView

export.excel.filename=Cartoon.xls

export.pdf.filename=Cartoon.pdf

export.xml.filename=Cartoon.xml

export.csv.filename=Cartoon.csv

export.rtf.filename=Cartoon.rtf

Error
-----------------------------------------------------------------------------------------------------------------

SEVERE: Servlet.service() for servlet jsp threw exception

java.lang.ClassNotFoundException: org.apache.commons.lang.UnhandledException

at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1688)

at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1533)

at java.lang.Class.getDeclaredConstructors0(Native Method)

at java.lang.Class.privateGetDeclaredConstructors(Class.java:2389)

at java.lang.Class.getConstructor0(Class.java:2699)

at java.lang.Class.newInstance0(Class.java:326)

at java.lang.Class.newInstance(Class.java:308)

at java.beans.Introspector.instantiate(Introspector.java:1449)

at java.beans.Introspector.findExplicitBeanInfo(Introspector.java:431)

at java.beans.Introspector.<init>(Introspector.java:380)

at java.beans.Introspector.getBeanInfo(Introspector.java:167)

at org.apache.jasper.compiler.Generator$TagHandlerInfo.<init>(Generator.java:3944)

at org.apache.jasper.compiler.Generator$GenerateVisitor.getTagHandlerInfo(Generator.java:2212)

at org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1640)

at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1539)

at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2376)

at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2428)

at org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1770)

at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1539)

at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2376)

at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2428)

at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2434)

at org.apache.jasper.compiler.Node$Root.accept(Node.java:475)

at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2376)

at org.apache.jasper.compiler.Generator.generate(Generator.java:3490)

at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:250)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:373)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)

at org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)

at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)

at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)

at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)

at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.sitemesh.webapp.contentfilter.ContentBufferingFilter.doFilter(ContentBufferingFilter.java:112)

at org.sitemesh.config.ConfigurableSiteMeshFilter.doFilter(ConfigurableSiteMeshFilter.java:163)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)

at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:471)

at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:402)

at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)

at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:240)

at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:258)

at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1174)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:901)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:809)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)

at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.sitemesh.webapp.contentfilter.ContentBufferingFilter.bufferAndPostProcess(ContentBufferingFilter.java:169)

at org.sitemesh.webapp.contentfilter.ContentBufferingFilter.doFilter(ContentBufferingFilter.java:126)

at org.sitemesh.config.ConfigurableSiteMeshFilter.doFilter(ConfigurableSiteMeshFilter.java:163)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)

at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)

at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:928)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)

at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)

at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:539)

at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:300)

at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)

at java.lang.Thread.run(Thread.java:680)

Apr 19, 2012 5:56:31 PM org.apache.catalina.core.StandardWrapperValve invoke

SEVERE: Servlet.service() for servlet [captionContest] in context with path [/CaptionContest] threw exception [java.lang.NoClassDefFoundError: org/apache/commons/lang/UnhandledException] with root cause