a cup of java

In my previous post I wrote about writing a web service provider using axis. But I did not mention a few things in that post.

1. How to make the service accessible to the outside world
2. How to write a Java client to avail the services

1. How to make the service accessible to the outside world?

As we are using the axis2.war as the way to deploy the services, we don’t really need to do anything. The deployment descriptor (web.xml) of axis2.war is equipped to handle it. But we need to make some URL mapping and stuffs like that.

- Add appropriate URL-servlet mapping  in the web.xml
- Add the name of the AAR in the service list

a. Deployment descriptor changes:

 <servlet>
   <servlet-name>AxisServlet</servlet-name>
   <display-name>Apache-Axis Servlet</display-name>
   <servlet-class>org.apache.axis2.transport.http.AxisServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>

 <servlet-mapping>
   <servlet-name>AxisServlet</servlet-name>
   <url-pattern>/servlet/AxisServlet</url-pattern>
 </servlet-mapping>

 <servlet-mapping>
   <servlet-name>AxisServlet</servlet-name>
   <url-pattern>/services/*</url-pattern>
 </servlet-mapping>

b. Add the name of the AAR in WEB-INF/services/services.list.

2. Writing a Java client to access the services

We have several ways to create the client stubs – JiXB, ADB etc. I followed ADB – Axis Data Binding. Axis provides a WSDL2Java tool to create client stubs from an existing WSDL. We can get the WSDL from http://localhost/services/SampleWs?wsdl.

WSDL2Java -uri SampleWs.wsdl -p subin.rnd.ws.client -d adb -s -o clientStubSrcDirectory_name

This will create the stub in the specified directory with name SampleWsStub.java. Once the stub is ready, we can write a client module which tries to access the deployed services.

WsClient.java

package subin.rnd.ws.client;

import subin.rnd.ws.client.SampleWsStub.WsInput;
import subin.rnd.ws.client.SampleWsStub.WsOutput;

public class WsClient
{
 public static void main(String[] args)
 throws Exception
 {
   SampleWsStub stub = new SampleWsStub("http://localhost/services/SampleWs");

   // Send the request
   SampleWsStub.DoSomething request = new SampleWsStub.DoSomething();
   WsInput anInput = new WsInput();
   anInput.setName("subin");
   request.setAnInput(anInput);

   // Get the response
   SampleWsStub.DoSomethingResponse response = stub.doSomething(request);
   WsOutput anOutput = response.get_return();

   System.out.println(anOutput.getResponseString());
 }
}

And that’s it !!!

This is a very basic post on writing a web service provider and consumer using Axis2. You can find such posts anywhere in the web. Here I’ve tried to make it as simple as I can.

Set up: What all we need to do?

1. Axis2 runtime.
I tried with WAR distribution from http://ws.apache.org/axis2/download/1_5/download.cgi
2. A web/app server. I am using Tomcat.

Using the Axis2 runtime & setting it up

Extract the Axis2 WAR distribution and keep it in the deploy directory of the server. In case of Tomcat keep it in webapps. This is how my directory structure look like.

The WEB-INF is the most important directory. Tell you why. Unlike our normal WEB-INF in archives, this directory hold some special sub-directories. Here goes which contains what.

classes – compiled Java classes. We can find some Axis specific classes here.
conf – axis.xml (Axis configuration file)
lib – All necessary Axis2 libraries (JARs)
modules – Don’t ask me. Even I’m not sure. Did I mention that I’m also a beginner?
services – All web service archives & services.list

Coding: What we need to write?

1. The service provider. A Java class.
2. service.xml. The web services descriptor.
3. build.xml. To build and deploy the web services archive.
4. The service consumer. Another Java class to consume the services offered

And we are good to go now. Let’s make our hands dirty with some Java code. This is very simple and kudos to Axis2.

The service provider: SampleService.java

package subin.rnd.ws;
public class SampleService
{
  public WsOutput doSomething(WsInput anInput)
  {
    System.out.println("doSomething()");
    WsOutput anOutput = new WsOutput();
    anOutput.setResponseString("I did some thing to " + anInput.getName());
    return (anOutput);
 }
}

WsInput is a sample input class to demonstrate that we can have more complex IO is possible. Similarly WsOutput is the output class. Instead of using WsInput / WsOutput for IO, we can use normal data types like integer, float, string etc too.

WsInput.java

package subin.rnd.ws;
import java.io.Serializable;
public class WsInput implements Serializable
{
 private String name;
 public void setName(String name)
 {
   this.name = name;
 }

 public String getName()
 {
   return (this.name);
 }
}

WsOutput.java

package subin.rnd.ws;
import java.io.Serializable;
public class WsOutput implements Serializable
{
 private String responseString;

 public void setResponseString(String response)
 {
   this.responseString = response;
 }
 public String getResponseString()
 {
   return (this.responseString);
 }
}

We have the Java part of the web-service ready. But that’s not enough. We need to deploy the web-service as an AAR – Axis Archive – file. An AAR  is just another zip file (like a JAR) with a funky extension . The AAR should contain the class files along with the services.xml – web service descriptor.

Web service descriptor: services.xml

<service name="SampleWs" scope="application">
 <description>Subin's sample webs service</description>
 <messagereceivers>
 <messagereceiver mep="http://www.w3.org/2004/08/wsdl/in-only"
 class="org.apache.axis2.rpc.receivers.RPCInOnlyMessageReceiver"/>
 <messagereceiver mep="http://www.w3.org/2004/08/wsdl/in-out"
 class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
 </messagereceivers>
 <operation name="doSomething" />
<parameter name="ServiceClass">subin.rnd.ws.SampleService</parameter>
</service>

The services.xml is the place where we define the details of the services being offered.

Build file: build.xml

<project name="my.webservice.test" default="build.aar">
<property name="deploy.dir" value=".../webapps/axis2.war/WEB-INF/services" />
<property name="file.name" value="subinws.aar" />

 <target name="build.aar">
   <javac srcdir="src" destdir="bin" />
   <echo>Copying services.xml to bin</echo>
   <copy file="META-INF/services.xml"
       tofile="bin/META-INF/services.xml" overwrite="true"/>
   <jar basedir="bin" destfile="${file.name}" />
   <echo>Deleting services.xml from bin</echo>
   <delete dir="bin/META-INF" />
   <copy file="${file.name}" tofile="${deploy.dir}/${file.name}"  />
 </target>

</project>

So I hope we have an AAR ready, which is copied to the services directory. But we’ve not done yet. Now we have to make an entry in services/services.list file. Just insert the name of the ARR file at the end of it – in this case “subinws.aar”.

Please wait for part 2.

I was just going through code.google.com, and just find a link titled “App Engine”. I was not at all surprised as they do this every time. With Google something is new every time. I went on reading. Oh God! Free J2EE app engine where we can host our archives ! This is one of the coolest things I was waiting to happen. The server where I hosted (and I’m still with them) my website does not have Java support and I spend many hours in writing Php codes after many hours of searching and testing, which I could have done in minutes with Java. And most importantly it’s almost FREE ! We have to pay them only if we are crossing the specified bandwidth & page view limits.

We can write code with Google’s Eclipse plug-in (with GWT support !), test them with in Eclipse and deploy them from Eclipse! Isn’t that cool? All you need is to have a Google account and just get it done. We can have up to nine applications each with a unique URL to access and we can even link them with our Google Apps too.

Check this video: Get an overview of App Engine’s new Java runtime and see a demo of a sample app from creation to deployment.

URL: http://www.youtube.com/watch?v=P3GT4-m_6RQ

-
For me this is nicest offer from Google in the recent times. I don’t know whether all of you are going to agree with this. But at least I’m happy. Hope all of you will find it nice.

Google App Engine: http://code.google.com/appengine/
FAQ: http://code.google.com/appengine/kb/
App Engine Blog: http://googleappengine.blogspot.com/
Getting started: http://code.google.com/appengine/docs/java/gettingstarted/

“Ouh, shiny! BBC’s Glow is finally out”

I found this article in ajaxian.com. Read the article here.

This article is about a new JavaScript framework recently open sourced by BBC. BBC Glow. BBC uses this framework in their websites. It’s too early for me to say whether this is a cool stuff to work with. Anyways you can try to make your hands dirty with “Glow”. Have a nice “Glow” time.

What is BBC Glow?
Glow is a JavaScript library which aims to make working with JavaScript and the DOM easier. It tries to do this by abstracting common tasks, hiding cross-browser issues, and providing a set of user interface widgets.

Source: http://www.bbc.co.uk/glow/

BBC Glow is free and open source.

Download Glow
Download source

Related links
What is Glow?
Getting started
More documentation

And we now have Firefox 3.5, which they claims to the better, faster, safer & smarter one yet, with lot of new features like private browsing, improved awesome bar, cross site XHR.

Features
Tips n’ Tricks
Download