Sahir Maredia's Blog

Java program to save a given URL into a file

2012-10-07T22:23:00.000+05:30

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Program to save web page in a file
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class SaveWebPage {

 /**
  * @param args
  */
 public static void main(String[] args) {
  if (args.length != 2) {
   System.out.println("Please provide valid arguments");
   return;
  }

  try {
   URL url = new URL(args[0]);
   BufferedReader br = new BufferedReader(new InputStreamReader(
     url.openStream()));
   BufferedWriter bw = new BufferedWriter(new FileWriter(args[1]));

   String input = "";
   while ((input = br.readLine()) != null) {
    bw.write(input);
    bw.newLine();
   }

   bw.close();
   br.close();
   System.out.println("Web page written successfully.");
  } catch (MalformedURLException e) {
   System.out.println("Error occured : " + e.getMessage());
  } catch (IOException e) {
   System.out.println("Error occured : " + e.getMessage());
  }
 }

}

Run this program as follows :

sahir@sahir-laptop:~/networklab$ javac SaveWebPage.java
sahir@sahir-laptop:~/networklab$ java SaveWebPage http://www.kotiasolutions.com/services.html services.txt
Web page written successfully.
sahir@sahir-laptop:~/networklab$

Java program to print parts of given URL

2012-10-07T22:16:00.000+05:30

import java.net.MalformedURLException;
import java.net.URL;

/**
 * Program to print all the parts of the given url
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class URLParts {

 /**
  * @param args
  */
 public static void main(String[] args) {
  if (args.length != 1) {
   System.out.println("Please provide valid arguments");
   return;
  }
  try {
   URL url = new URL(args[0]);
   System.out.println("====== Given URL is : " + args[0] + " ======");
   System.out.println("Protocol : " + url.getProtocol());

   // if port not specified as part of url, getting default port
   int port = url.getPort() == -1 ? url.getDefaultPort() : url
     .getPort();
   System.out.println("Port : "
 + port);
   System.out.println("Host : " + url.getHost());
   System.out.println("Path : " + url.getPath());
   System.out.println("File Name : " + url.getFile());
   System.out.println("Query : " + url.getQuery());
  } catch (MalformedURLException e) {
   System.out.println(e.getMessage());
  }

 }

}

Run this program as follows :

sahir@sahir-laptop:~/networklab$ javac URLParts.java
sahir@sahir-laptop:~/networklab$ java URLParts http://www.kotiasolutions.com/services.html?service=web
====== Given URL is : http://www.kotiasolutions.com/services.html?service=web ======
Protocol : http
Port : 80
Host : www.kotiasolutions.com
Path : /services.html
File Name : /services.html?service=web
Query : service=web
sahir@sahir-laptop:~/networklab$

Simple nslookup java clone

2012-10-07T22:12:00.002+05:30

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * Program to perform simple functionality of NSLookUp (simple nslookup clone)
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class NSLookup {

 /**
  * @param args
  */
 public static void main(String[] args) {
  if (args.length != 1) {
   System.out.println("Please provide valid arguments");
   return;
  }

  try {
   InetAddress ipaddress = InetAddress.getByName(args[0]);
   System.out.println("Name : " + ipaddress.getHostName());
   System.out.println("Address : " + ipaddress.getHostAddress());
  } catch (UnknownHostException e) {
   System.out.println("Error occured : " + e.getMessage());
  }
 }

}

Run this program as follows:

sahir@sahir-laptop:~/networklab$ javac NSLookup.java
sahir@sahir-laptop:~/networklab$ java NSLookup google.com
Name : google.com
Address : 74.125.236.163
sahir@sahir-laptop:~/networklab$ java NSLookup 74.125.236.163
Name : maa03s16-in-f3.1e100.net
Address : 74.125.236.163
sahir@sahir-laptop:~/networklab$

Java program to find the whether given IP is IPv4 or IPv6

2012-10-07T22:09:00.000+05:30

import java.util.regex.Pattern;

/**
 * Program to find whether given ip is IPv4 or IPv6 address
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class IPType {

 private static final String IPv4 = "(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([01]?\\d\\d?|2[0-4]\\d|25[0-5])";
 private static final String IPv6 = "([0-9a-f]{1,4}:){7}([0-9a-f]){1,4}";

 /**
  * @param args
  */
 public static void main(String[] args) {
  if (args.length != 1) {
   System.out.println("Please provide IP address as argument");
   return;
  }
  String ipaddress = args[0];
  
  Pattern ipv4 = Pattern.compile(IPv4);
  Pattern ipv6 = Pattern.compile(IPv6);
  if (ipv4.matcher(ipaddress).matches()) {
   System.out.println("Given IP Address : " + ipaddress + " is IPv4");
   return;
  } else if (ipv6.matcher(ipaddress).matches()) {
   System.out.println("Given IP Address : " + ipaddress + " is IPv6");
   return;
  } else {
   System.out.println("Given string is an invalid IP address");
  }
 }

}

Run this program as follows :

sahir@sahir-laptop:~/networklab$ javac IPType.java
sahir@sahir-laptop:~/networklab$ java IPType 192.168.1.1
Given IP Address : 192.168.1.1 is IPv4
sahir@sahir-laptop:~/networklab$ java IPType 0000:ffff:1234:4567:0000:4321:4567:ffff
Given IP Address : 0000:ffff:1234:4567:0000:4321:4567:ffff is IPv6
sahir@sahir-laptop:~/networklab$

Java program to find all IP addresses of given Host

2012-10-07T21:13:00.000+05:30

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
 * Program to print all ip addresses of given domain
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class FindIP {

 /**
  * @param args
  */
 public static void main(String[] args) {
  if (args.length != 1) {
   System.out.println("Please provide a valid input");
   return;
  }
  try {
   InetAddress[] ipaddresses = InetAddress.getAllByName(args[0]);

   for (InetAddress ip : ipaddresses)
    System.out.println(ip.getHostAddress());
  } catch (UnknownHostException e) {
   System.out.println("Error occured : " + e.getMessage());
  }
 }

}

Run the program as follows:

sahir@sahir-laptop:~/networklab$ javac FindIP.java
sahir@sahir-laptop:~/networklab$ java FindIP google.com
74.125.236.163
74.125.236.164
74.125.236.165
74.125.236.166
74.125.236.167
74.125.236.168
74.125.236.169
74.125.236.174
74.125.236.160
74.125.236.161
74.125.236.162
2404:6800:4007:802:0:0:0:100e
sahir@sahir-laptop:~/networklab$

Java Program to find Computer name, IP Address and list all network interfaces

2012-10-07T20:06:00.000+05:30

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Collections;
import java.util.Enumeration;

/**
 * Program to display current computer name, IP Address and network interfaces
 * 
 * @author sahir maredia (Kotia Solutions)
 * 
 */
public class ComputerName {

 /**
  * @param args
  */
 public static void main(String[] args) {
 try {

  InetAddress ipaddress = InetAddress.getLocalHost();
  System.out.println("Computer Host Name : "
    + ipaddress.getHostName());
  System.out.println("IP Address of Localhost : "
    + ipaddress.getHostAddress());

  // getting list of network interfaces
  Enumeration<NetworkInterface> interfaces = NetworkInterface
    .getNetworkInterfaces();

  System.out.println();
  System.out
    .println("================ Following are the available network interfaces ===============");
  System.out.println();
  if (interfaces == null) {
   System.out.println("No network interfaces found");
  } else {

   for (NetworkInterface netIf : Collections.list(interfaces)) {
    System.out.println("Display Name : "
      + netIf.getDisplayName());
    System.out.println("Name : " + netIf.getName());
    System.out.println();
   }
  }
 } catch (UnknownHostException ex) {
  System.out.println("Error Occured : " + ex.getMessage());
 } catch (SocketException e) {
  System.out.println("Error Occured : " + e.getMessage());
 }
 }

}

Run the program as follows :

sahir@sahir-laptop:~/temp/networklab$ javac ComputerName.java
sahir@sahir-laptop:~/temp/networklab$ java ComputerName
Computer Host Name : sahir-laptop
IP Address of Localhost : 127.0.1.1

================ Following are the available network interfaces ===============

Display Name : wlan0
Name : wlan0

Display Name : lo
Name : lo

sahir@sahir-laptop:~/temp/networklab$

Add Custom Application to Ubuntu Dashboard

2012-10-06T23:06:00.000+05:30

To add a custom application icon to Ubuntu dashboard, create a file with name AppName.desktop in ~/.local/share/applications Put Following into that file

[Desktop Entry]
Name=Application Name
Comment=Application Description
Exec=<path to executable;>

Icon=<path to application icon>
Terminal=false
Type=Application
StartupNotify=true
Keywords=<some keywords>

Deploying and Managing PostgreSQL on OpenShift

2012-05-27T11:48:00.001+05:30

The Object Oriented Life: Useful Eclipse Plugins that didn't made it to the ...

2012-01-13T22:25:00.000+05:30

The Object Oriented Life: Useful Eclipse Plugins that didn't made it to the ...: Eclipse IDE project is started aiming to provide a universal tool set for development. Open Source IDE, mostly provided in Java, but the...

URL to add facebook Page Tab

2012-01-09T15:37:00.002+05:30

http://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID&display=popup&next=REDIRECT_URI

Update - We can also use this url

<a href="http://facebook.com/add.php?api_key=YOUR_APP_KEY&pages=1&page=YOUR_PAGE_ID" target="_blank">PAGE NAME</a>

Making Admin Panel using YIi Framework

2012-01-08T20:09:00.000+05:30

Recently, I have started coding in PHP. After coding for 2 -3 weeks, I started missing all those wild cards that frameworks provided me while coding in Java. All the basics things required in any project are taken care by those frameworks. We just need to configure and things are ready.
This magic of getting things easily made me to search for frameworks in PHP. Earlier, I have used Joomla and Code Igniter(CI). I believe Joomla is great CMS, but using it for any other purposes does not give me flexibility. Code Igniter, I used it long long ago. I came across article saying CI vs Yii vs Kohana. This comparison interested me to use Yii Framework. I found the documentation to be good and also community is good. I have started using this framework. I like the Active Record support which fills the space of hibernate framework.
First thing I started with is to create a admin panel. I got a very good link through google. It explains all and we can easily create Joomla kind of admin panel in our applications.
Link to tutorial : http://bit.ly/wCDLab

Configure Database Server LoginModule Realm in Jboss AS 7

2011-12-31T17:43:00.000+05:30

If we want to do a Database login for JavaEE6 application, We need to configure the DatabaseServerLoginModule of Jboss by creating a Realm. Put following lines in standalone.xml ( or domain.xml) :

Replace values with your respected values. If you are using custom database module class replace code="Database" with code="<your class name>"
Now the realm is configured into server, We need to tell our application to use this realm. This can be achieved using web.xml

 
  FORM
  MyRealm
  
   /login.jsp
   /loginerror.jsp
  
 
 
  SuperAdmin
 
 
  Admin
 
 
  Manager
 
 
  Employee

From lines 1 to 8 we inform the application to make use of FORM method to authenticate users with Realm MyRealm and also provide the login and error pages.
Next we need to declare the security roles in the application. We have declared 4 roles SuperAdmin, Admin, Manager and Employee from lines 9 to 20.
Now we have configured the application we will add security constraint in web.xml to our application as below.


  
   MyApplication
   /administration/*
   GET
   POST
  
  
   SuperAdmin
   Admin
  
 
 
  
   Unprotected area
   /resources/*

We added two security constraints. First is to allow only SuperAdmin and Admin to enter the admin panel. Another example is when you have protected entire site but want to allow access to resources to all.

11 Things every Software Developer should be doing in 2012.

2011-12-31T10:50:00.001+05:30

Link : http://bit.ly/uo1DwM

JPA Performance, Don't Ignore the Database

2011-12-24T21:39:00.000+05:30

http://weblogs.java.net/blog/caroljmcdonald/archive/2009/08/28/jpa-performance-dont-ignore-database-0

Install Postgresql 9.1 in Ubuntu 9.04

2011-12-16T22:56:00.000+05:30

first install python-software-properties:
sudo apt-get install python-software-properties

now add repository and update apt.
sudo add-apt-repository ppa:pitti/postgresql
sudo apt-get update

now instal postgresql
sudo apt-get install postgresql-9.1 libpq-dev

Now change the postgres user password (still running as root):
su postgres
psql -d postgres -U postgres
alter user postgres with password 'a';
\q

To install GUI client pgsql
sudo apt-get install pgadmin3

original article: http://bit.ly/sUFCgb

How to Accomplish More by Doing Less - Tony Schwartz - Harvard Business Review

2011-12-16T17:56:00.000+05:30

How to Accomplish More by Doing Less - Tony Schwartz - Harvard Business Review.

Enable AutoComplete commands in Pinguy OS 11.04

2011-12-16T16:35:00.000+05:30

To enable bash completion in interactive shells do following steps:


$ sudo vi /etc/bash.bashrc

uncomment following line in it


# enable bash completion in interactive shells
if [ -f /etc/bash_completion ]; then
. /etc/bash_completion
fi

Restart your terminal and its done!!!

Fix GPG error:....NO_PUBKEY

2011-12-16T16:22:00.000+05:30

In Ubuntu, when we try to update the system we sometimes get error for GPG No_PUBKEY as follows:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C1622487AAA521A8

This does no harm as its not a security issue but its very annoying everytime getting the same error. It happens because you don't have a suitable public key for a repository. Follow this steps to get rid of the error:

gpg --keyserver keyserver.ubuntu.com --recv 9BDB3D89CE49EC21

Which retrieves the key from ubuntu key server and then this:

gpg --export --armor 9BDB3D89CE49EC21 | sudo apt-key add -

Which adds the key to apt trusted keys. This will solve you problem.

The solution can be found here & here.

Sun Certified Java Programmer 310-065 - Mr.Bool Courses

2011-12-14T16:51:00.000+05:30

Sun Certified Java Programmer 310-065 - Mr.Bool Courses

Real Java Geeks

2011-12-13T23:57:00.000+05:30

Code hard! And get out of your cubicles! Video created for the Community Keynote at JavaOne Brasil.

Create intro flash / page in Joomla

2011-12-12T22:23:00.001+05:30

Recently I am doing a website in joomla and I wanted to have an intro page for it. By default, there is no facility for it in joomla by default. Dont worry. Create an index.html file and put in the root directory. It will first take up that html file and you have successfully created an intro page. On this intro page provide a link to index.php file and you just entered into your joomla site. What if your hosting takes index.php as default? Then create .htaccess file and add following line in it:

       DirectoryIndex index.html index.php

This tells apache to load index.html as default page. replace index.html with your intro filename. Another option is to install joomla inside sub-directory and put intro file outside joomla directory and point index.php inside that sub directory.

Reset Apache2 on Ubuntu

2011-12-12T17:41:00.000+05:30

Recently I was experimenting on apache2 and edited many config files. Soon I realised that PHP was not working properly on it. While installing joomla it was failing. So I removed apache2 using command:

     sudo apt-get purge apache2

The problem was I didnt removed apache2 completely. Then I quicked googled and find out the correct way of getting it working back use following snippet.

APACHE_PKGS=`sudo dpkg --get-selections | grep apache | cut -f 1`
# Make sure things are sane:
echo $APACHE_PKGS
# Example output: apache2 apache2-mpm-prefork apache2-utils apache2.2-common \
# libapache2-mod-php5 libapache2-mod-python libapache2-svn
# Likely if you have a Python application:
# libapache2-mod-python libapache2-mod-python-doc libapache2-mod-wsgi
# Or if you roll with the PHP:
# libapache2-mod-php5
sudo apt-get remove --purge $APACHE_PKGS
# You might want to consider not re-installing the whole list;
# instead dump it out, audit, and install what you need:
sudo apt-get install $APACHE_PKGS

After this apache2 got resetted and working as it was freshly installed with all configurations replaced.
Reference : http://bit.ly/uBxq7L

Quote

2011-12-12T16:44:00.001+05:30

"Never take decision when angry and Never make promise when happy."

Data Structures: Stack

2011-12-10T23:51:00.001+05:30

Data Structures can be defined as arrangement and storage or organization of data so that inserting, retrieving and modifying the data becomes efficient, faster and easier. There are different kinds of data structures available and can be used in our applications according to our requirement. Any application we develop is all about manipulating the data. So data structures are always required to write any application. Any data structure we consider can be implemented in any language of your choice. Hence data structures are independent of language. Data Structure consists of two parts:

Data.
Operations on that data.

We all know about the data. What are operations? Any data structure will commonly give insert, read, update and delete operations. In addition to these operations specific functions can be written for that data structure like if we consider List we can have sort() functionality in addition to the above functionality. As Data Structures are important of the application development, I have decided to write all the data structures that I know on my blog. To start with the simplest one Stack.
STACK: Stack can be defined as LIFO kind of data structure i.e last in first out. I remember an example which my professor gave us. In mess, the plates in which we are served food are all kept piled one upon another. Stack is same as that pile of plates. The plate which was put first on table will be the last to be served and last becomes first to be served. Stack is very restricted data structure. It has only two operations push() and pop(). Push is used to put any data into the stack. It is equivalent to arranging the plates. Pop is used to retrieve the data back from the stack. It is equivalent to serving the food to people. Stack can be graphically can be imagined as:

In the stack shown above. Element in colour red was first to be inserted and element in navy blue was the last element inserted. Now if I call push() operation on above stack element with orange colour will be inserted above fourth element as shown.

Now if i call pop() operation on above stack last inserted element i.e. orange element will be removed from the stack getting us back to the previous stack.
Stack is used to manage memory of the program during runtime. When a sub-routine is called current state of memory is saved into the stack which corresponds to the push operation. when sub-routine execution finishes, pop() operation is called to get the previous state of the program.
This brings us to the end of stack data structure. Please write in your comments and any queries. In the next post, I ll be explaining another data structure Link List. Thank you.

You're a Bad Manager. Embrace It.

2010-10-07T13:22:00.000+05:30

You're a Bad Manager. Embrace It.: "You manager developers and you'd like to think you're a good manager... but look at the evidence. Most, if not all, of your projects are late. Your team often delivers products riddled with bugs. Quite a few never ship at all. How can you be a good manager if you constantly fail? Isn't getting the job done a big part of being a good manager? Let's look at this situation.Let's look at a few of..."