Forrester’s authors say that its report, “The Future of Java,” is not a Java obituary. Java is still dominant in the enterprise but no programming language has retained a central position through multiple platform changes. Java will evolve just as Assembler, C and COBOL did. More so, the core message here is for application developers and how applications are distributed.

…

Oracle controls the future of Java but its road map has been accepted and that means no major disruptions for enterprise customers. But it’s clear that Java is no longer the center for technology innovation. The innovation is now on the platforms and with Ruby and open environments such as HTML 5.

via Why The Future of Java is with Large Customers, not Innovative, Young Developers.

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My theory goes like this: Good java developers are hard to find because fewer and fewer of them are being created. New developers are not choosing java to “cut their teeth” on. And I suspect that coming from whatever they are coming from, java doesn’t look appealing.

via I think I figured out why good Java developers are so hard to find « I love groovy.

The excerpt above came from a blog post I read this morning. It made me ask the question: Is Java on it’s way to being phased out by newer JVM languages? Judging by some of the comments to this article at least a few believe so. But which JVM language has the potential to replace it? I found this article: The Next Big JVM Language which evaluates a few contenders.

Java is not sexy to the next generation of developers. The language is considered old, bloated, overly complex and has more than a few legacy quirks which fuel many language debates. Scala, Jython/Python, JRuby/Ruby and Groovy all seem to be popular alternatives.

headpower :

I’m a 15 year old person studying to become a developer (mostly in my free time), and I can tell you that Java is not something I would ever consider. I consider myself to “know” Python and [Objective-]C, but, Java isn’t even on my radar. I know some people my age who would use Java, but to me it just seems outdated and bloated to most of us, I think.

Since I guess I’m the “next generation”, it doesn’t seem that your situation is going to get any better…

According to these sources:  http://www.numberof.net/number-of-java-developers/ and http://jaxenter.com/how-many-java-developers-are-there-10462.html there are 9,007,346 Java developers world-wide. That’s a very large and active user base. While it seems that Java may not be the choice of the next-generation of developers it is still the primary language for over 9 million developers.

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JavaOne and Oracle Develop 2010

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Receiving null is confusing. When you make a function call and the result is null what does it mean? Was the data not found? Was there an exception in the function that was silently swallowed resulting in the return of a null object? You’re not really sure if null is an expected return value. If no exception is thrown then you just kind of assume that null is a valid return value. However, you can’t really do anything with the returned null object so what do you do now?

Here are a couple of alternatives to returning null:

Use the Empty Collection Methods

If you are working with returning collection objects from your function you should return an empty collection rather than a null object. This is very easy to do with the Collections class. There are three static methods available:

• Collections.emptyList()
• Collections.emptySet()
• Collections.emptyMap()

An empty List is easily instantiated for return as shown here:

   List<String> myList = Collections.emptyList();

Returning an empty List eliminates the required check for null by the function caller. Now instead of having code which looks like this:

   List<String> names = getNames();
   if(names != null) {
      for(String name : names) {
         System.out.println(name);
      }
   }

You can simply write the following without worrying about a NullPointerException:

   List<String> names = getNames();
   for(String name : names) {
      System.out.println(name);
   }

This second example is much cleaner, easier to read and understand. Returning empty Collections is much safer as well since it avoids the potential run time exception: NullPointerException.

An unchecked exception represent defects in the program (bugs) - often invalid arguments passed to a non-private method. To quote from The Java Programming Language, by Gosling, Arnold, and Holmes : “Unchecked runtime exceptions represent conditions that, generally speaking, reflect errors in your program’s logic and cannot be reasonably recovered from at run time.” [1]

Certainly an empty collection is not a bug! So lets just return an empty collection rather than a null reference. In addition, testing for an empty collection is a lot more intuitive than testing for null.

   List<String> names = getNames();
   if(names.isEmpty()) {
      //throw an Exception
      //or do something else
      //or do nothing at all

   }

Throw an Exception

It’s perfectly acceptable to throw a custom checked exception alerting the calling client that the requested object cannot be populated or retrieved. This approach is much more revealing and forces the calling client to handle the potential problem. It also eliminates the need to check the returned object for null.

A checked exception is guaranteed to be handled so you gain more control over your program. A RuntimeException may or may not be handled by the caller and will bubble up until either it is caught or reaches the top of the caller chain.

Conclusion

Nulls are useful under certain conditions when null values are expected. However, for the above conditions with collections and data retrieval I feel it has been abused. Use the empty collection and avoid returning null objects whenever possible. It will make code cleaner, easier to read and debug.

Citations:

1. “checked versus uncheck exceptions” JavaPractices.com. 2010 Hirondelle Systems. 6 June 2010 <http://www.javapractices.com/topic/TopicAction.do?Id=129>

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A Simple Service

To start out you should create an interface defining your business methods. I will keep the implementation extremely simple so we can focus on the details of web services. Here’s our interface named SimpleServiceWS

public interface SimpleServiceWS {

	public String simpleMethod();

}

The next step is to create a plain java class (POJO) which implements this interface. I’ll name it SimpleServiceImpl

public class SimpleServiceImpl implements SimpleServiceWS {

	public String simpleMethod() {
		return "Simple response";
	}

}

Please note that it is not required to create and implement an interface and almost every web service example I found did not do so. I feel it is good practice and consistent with Java programming practices to program against interfaces.

What we have so far is just a plain Java class (POJO) that returns a simple string. Now we have to decorate our class with some annotations to make it behave as a web services.

import javax.jws.WebService;

@WebService(
		serviceName="SimpleService",
		portName="SimpleServicePort",
		endpointInterface="net.franksalinas.javablog.SimpleServiceWS")
public class SimpleServiceImpl implements SimpleServiceWS {

	public String simpleMethod() {
		return "Simple response";
	}

}

I added the @WebService annotation and supplied some values to the annotation attributes. You can simply add the @WebService annotation without specifying any of the attributes and they will pick up default values based on the class and package names. However, there is one exception. If you choose to define and implement an interface you must do two things:

1. You must decorate the interface with the @WebService annotation.
2. You must also supply the endpointInterface annotation attribute with the fully qualified name of the interface in the implementation class.

import javax.jws.WebService;

@WebService()
public interface SimpleServiceWS {

	public String simpleMethod();

}

As far as code goes this is all there is to it. The remaing steps describe how to package and deploy these objects.

Package and Deploy

As I mentioned above we will package and deploy these classes as a servlet implementation. I am most familiar with JBoss so that is the application server I will use but any servlet container should work fine.

Create a new xml file named web.xml and define the servlet mappings for the SimpleServiceImpl class as shown here.

<?xml version="><?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC
	"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
	"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
	<servlet>
		<servlet-name>SimpleServiceWS</servlet-name>
		<servlet-class>net.franksalinas.javablog.SimpleServiceImpl</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>SimpleServiceWS</servlet-name>
		<url-pattern>/SimpleService</url-pattern>
	</servlet-mapping>
</web-app>

Now create a WEB-INF directory and place this file there. Compile your Java files and place them in a folder named classes. Create a folder named dist. Copy the WEB-INF and classes directory to this new folder. Now create a JAR file named SimpleService.war containing the contents of dist directory. (Visit http://en.wikipedia.org/wiki/Sun_WAR_(file_format) for more info on the WAR file structure.)

You should now have a WAR file with the following structure:

META-INF/
META-INF/MANIFEST.MF
WEB-INF/
WEB-INF/web.xml
classes/
classes/net/
classes/net/franksalinas/
classes/net/franksalinas/javablog/
classes/net/franksalinas/javablog/SimpleServiceImpl.class
classes/net/franksalinas/javablog/SimpleServiceWS.class

Now you can copy this SimpleService.war file to your application server’s deployment directory (<jboss_home>/server/default/deploy) and start the server. Your web service will be deployed. On JBoss you can see the deployment and access the WSDL for the service at url http://127.0.0.1:8080/SimpleService/SimpleService?wsdl

That’s all there is to it!

Note that we did not implement the javax.servlet.http.HttpServlet interface in the service class. It is not required but may be considered good practice to do so depdending on your implementation.

Summary

In this example we created a simple web service using JAX-WS and packaged and deployed the implementation as a servlet configuration. We learned that web services are nothing more than plain old Java objects (POJOs) that are decorated with a few simple annotations and that servlet configurations do not require the web service class to implement the javax.servlet.http.HttpServlet interface. We covered packaging the code as a WAR file and deploying on the JBoss application server.

This is a very simple example and there’s a lot more material to cover. I hope you found this posting informative and helpful. You can download all the source code for this example here: SimpleService.zip.

Related posts:

1. Web Services on JBoss I’ve been working on a project which requires developing some...
2. The EJB Specification, Concurrency, and Batch Processing The EJB specification does not leave much room for implementing...

Java tip: How to read files quickly | Nadeau Software

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