Moving to Servlet 3.0

2010-06-13T03:55:00.000-07:00

Its time to hands on servlet 3.0 specification that has approved as JSR 315 and coming as a part of J2EE6. Currently JBOSS 6,Jetty 8 and of course Glassfish V3 is supporting these specification. In my examples i will be using JBOSS 6.0.0-M2

A brief on new specification feature of Asynchronicity although we can provide this feature by using Ajax. Having an inherent quality of server side means we would not be any more Ajax altogether. Somebody should correct me if I am wrong. AsyncContext,AsyncListener, AsyncEvent are the added interfaces having methods for asynchronicity purpose also there are some methods added in ServletRequest interface.

It’s easy to define asynchronicity nature with annotations.

@WebServlet (urlPatterns= {"/MyAsyncServlet3"}, asyncSupported=true)

One of the motivations of asynchronous programming could be slow services that hold resources keep in background and make other call in process.

With Servlet 3.0 Annotations web.xml presence is optional J . We can define Servlets, Fileters, Listenrs using annotations.

@WebServlet (name="MyServlet3", urlPatterns= {"/MyServlet3"},

initParams= { @WebInitParam(name="param", value="value") })

@WebFilter (filterName="myfilter", urlPatterns= {"/MyServlet3})

@WebListener ()

Let’s have an example to see how to define servlet with annotations and running it.

1.Create a dynamic project in eclipse I have taken name here as blogsample

2. Create a servlet MyServlet3 and MyAsynchServlet inside directory blog.sample.As eclipse 3.5 by default does not support servlet3.0 you have to take it as a dependency in your classpath

package blog.samples;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebInitParam;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* This class represents an example of Servlet 3.0

* Specification simple servlet with annotation

* @author shakil.akhtar

@WebServlet(name="MyServlet3", urlPatterns={"/MyServlet3"},

initParams={ @WebInitParam(name="fname", value="Shakil") })

public class MyServlet3 extends HttpServlet{

@Override

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

PrintWriter out = response.getWriter();

String fname = getServletConfig().getInitParameter("fname");

out.println("Hello "+fname+"!");

out.close();

}

@Override

protected void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request,response);

}

package blog.samples;

import java.io.IOException;

import java.util.Queue;

import java.util.concurrent.ConcurrentLinkedQueue;

import javax.servlet.AsyncContext;

import javax.servlet.AsyncEvent;

import javax.servlet.AsyncListener;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* This is an example of asynchronous request

* @author shakil.akhtar

@SuppressWarnings("serial")

@WebServlet(urlPatterns = { "/MyAsyncServlet" }, asyncSupported = true)

public class MyAsynchServlet extends HttpServlet {

private static final Queue asycnReqQueue = new ConcurrentLinkedQueue();

public void doGet(HttpServletRequest request, HttpServletResponse response) {

final AsyncContext ctx = request.startAsync();

ctx.setTimeout(30000);

asycnReqQueue.add(ctx);

//A listener that will listen Async request cycle

ctx.addListener(new AsyncListener() {

@Override

public void onError(AsyncEvent asyncEvent) throws IOException {

System.out.println("Inside onError");

}

public void onComplete(AsyncEvent asyncEvent) throws IOException {

System.out.println("Inside onComplete");

asycnReqQueue.remove(ctx);

}

public void onTimeout(AsyncEvent asyncEvent) throws IOException {

System.out.println("Inside onTimeout");

asycnReqQueue.remove(ctx);

}

@Override

public void onStartAsync(AsyncEvent asyncEvent) throws IOException {

System.out.println("Inside onStartAsync");

}

});

asycnReqQueue.add(ctx);

}

public void doPost(HttpServletRequest request, HttpServletResponse response) {

doGet(request, response);

}

3. Remove web.xml as we are using annotation in our example

4- Export war from eclipse and name it as blogsample.war.

5- To run your example you need a server that is supporting servlet 3 specification.I am using here Jboss 6.0.0-M2 .you can download it from http://www.jboss.org/jbossas/downloads/ .Extract zip somewhere and deploy blogsample.war into $JBOSS_HOME\ server\default\deploy directory. Now run Jboss and type http://localhost:8080/blogsample/MyServlet3 on browser. You will see output on browser as Hello Shakil!. Now test Async example hit browser with http://localhost:8080/blogsample/MyAsyncServlet this will show

   15:50:43,281 INFO  [STDOUT] Inside onTimeout

   15:50:43,281 INFO  [STDOUT] Inside onComplete

   On your server console.

You have seen how to create servlets with annotations. There are many more in servlet3 specifications like dynamic registrations of servlets and filters, web frameworks pluggability, build in support for handling file uploads, modularization of web.xml.You can have look on these specifications on http://java.sun.com/products/servlet/download.html

Akhtar's Blog

Moving to Servlet 3.0