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This tutorial will take you through the steps required in developing, deploying and testing a RESTful Web Service Client in Apache Geronimo for a web services which are already deployed on the server

We will be creating a Web based Client which can access the RESTful web service via GET and POST methods. You can easily create this client without any external tools except that of a server environment.

To run this tutorial, as a minimum you will be required to have installed the following prerequisite software.

Sun JDK 5.0+ (J2SE 1.5)
Apache Geronimo 2.x
Eclipse IDE for Java EE Developers - Europa release
Geronimo Eclipse Plug-in 2.x

Details on installing Eclipse are provided in the Development environment section.

This tutorial assumes that you have completed the Developing a simple RESTful Service tutorial. Here we will try to develop the client for the web service deployed in the above mentioned tutorial.

This tutorial will take you through the following steps:

Create a Dynamic Web Project to consume the Web Service

From Eclipse main menu, select File->New->Other
In the New dialog, select Web->Dynamic Web Project and click Next
Type jaxws-rest-converterclient as the Project Name and click Next
On the Project Facets page, the default selections are enough.
Make sure that the check box Generate Deployment Descriptor is selected and click Next
On the Geronimo Deployment Page modify the Group Id to org.apache.geronimo.samples.jaxws.rest and the Artifact Id to jaxws-rest-converterclient.
Click Finish

Developing the Web based Client

Right Click the jaxws-converterclient, and Select New->JSP
Name the jsp as index.jsp and click Finish
Add the following code to the index.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>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>RESTful Client</title>
</head>
<body>
<center>
<h1>RESTful Client</h1>
<br><br>
<a href="post.jsp">Test via Post</a>
<table bgcolor="#CCC">
<tr><td>
<form action="index.jsp" >Dollars: <input type="text"
	name="query"> <input type="submit" value="Submit"></form>
</td></tr>
</table>
</center>
<jsp:include page="/ConverterHandler" />
</body>
</html>

Right click again and add another jsp named post.jsp
Add the following code to post.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>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>RESTful Client</title>
</head>
<body>
<center>
<h1>RESTful Client</h1>
<a href="index.jsp">Test via Get</a>
<br><br>
<table bgcolor="#CCC">
<tr><td>
<form method="post" enctype=multipart/form-data action="post.jsp" >Enter full file Name: <input type="file"
	name="query"> <input type="submit" value="Submit"></form>
</td></tr>
</table>
</center>
<jsp:include page="/ConverterHandler" />
</body>
</html>

Right click again and add a Servlet named ConverterHandler
Add the following code to ConverterHandler.java


package org.apache.geronimo.samples.jaxws.rest;

import java.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.methods.*;
import org.w3c.dom.*;
import org.xml.sax.SAXException;

public class ConverterHandler extends javax.servlet.http.HttpServlet implements
		javax.servlet.Servlet {
	static final long serialVersionUID = 1L;

	public ConverterHandler() {
		super();
	}

	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {

		PrintWriter out = response.getWriter();
		String query = request.getParameter("query");
		if (query != null && query.length() > 0) {
			out.println("<center>");
			out.println("<br><br><br>");
			String requestquery = "http://localhost:8080/jaxws-rest-converter/converter?amount="
					+ query;
			HttpClient client = new HttpClient();
			GetMethod method = new GetMethod(requestquery);
			int statusCode = client.executeMethod(method);
			if (statusCode != HttpStatus.SC_OK) {
				System.err.println("Method failed: " + method.getStatusLine());
			}
			InputStream rstream = null;
			rstream = method.getResponseBodyAsStream();
			Document queryresponse = null;
			try {
				queryresponse = DocumentBuilderFactory.newInstance()
						.newDocumentBuilder().parse(rstream);
			} catch (SAXException e) {
				e.printStackTrace();
			} catch (ParserConfigurationException e) {
				e.printStackTrace();
			}

			XPathFactory factory = XPathFactory.newInstance();
			XPath xPath = factory.newXPath();
			NodeList nodes = null;
			try {
				nodes = (NodeList) xPath.evaluate("/return", queryresponse,
						XPathConstants.NODESET);
			} catch (XPathExpressionException e) {
				e.printStackTrace();
			}
			int nodeCount = nodes.getLength();
			for (int i = 0; i < nodeCount; i++) {
				// Get each xpath expression as a string
				String rupees = null;
				String euros = null;
				try {
					rupees = (String) xPath.evaluate("dollarToRupeesResponse",
							nodes.item(i), XPathConstants.STRING);
					euros = (String) xPath.evaluate("rupeesToEurosResponse",
							nodes.item(i), XPathConstants.STRING);

				} catch (XPathExpressionException e) {
					e.printStackTrace();
				}
				out.println(query + " Dollars equals to " + rupees + " Rupees");
				out.println("<br>");
				out.println(rupees + " Rupees equals to " + euros + " Euros");
			}
			out.println("</center>");
		}

	}

	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// Has to be Completed
	}
}

Here the servlet might notify that some imports are not resolved. We need to add two external jar files to resolve these errors.
The jar files that needed to be added in the build path are:
commons-codec-1.3.jar - <GERONIMO_INSTALL_DIR>\repository\commons-codec\commons-codec\1.3\commons-codec-1.3.jar
commons-httpclient-3.0.1.jar - <GERONIMO_INSTALL_DIR>\repository\commons-httpclient\commons-httpclient\3.0.1\commons-httpclient-3.0.1.jar

Let us walkthrough the code of ConverterHandler servlet.

We will create a HttpClient object and GetMethod object for our requestquery. Then we will execute the method on our client object.
The response after executing the method will be taken as a stream so as to parse the XML elements in response message sent by the Web Service.

Here we used XPath to process XML response messages sent by web service.

XPath (XML Path Language) is a language for selecting nodes from an XML document with very advanced features.

Our response message sent by web service may look like this:

<return>
    <dollarToRupeesResponse>933.34</dollarToRupeesResponse>
    <rupeesToEuroResponse>933.34</rupeesToEuroResponse>
</return>

We will first try to get the NodeList present between <return> elements, Then we evaluate each child node to get the results.

This concludes the development section of our web based client.

Setting Up the Deployment Plan

As two external jars have been added to the project's build path, One needs to specify them as dependencies so that at runtime application can resolve the classes.
Expand WebContent/WEB-INF directory and open geronimo-web.xml
Add the following code to geronimo-web.xml


<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns8:web-app xmlns="http://geronimo.apache.org/xml/ns/j2ee/connector-1.2"
	xmlns:ns2="http://geronimo.apache.org/xml/ns/deployment-1.2"
	xmlns:ns3="http://geronimo.apache.org/xml/ns/naming-1.2"
	xmlns:ns4="http://openejb.apache.org/xml/ns/openejb-jar-2.2" 
	xmlns:ns5="http://openejb.apache.org/xml/ns/pkgen-2.1"
	xmlns:ns6="http://geronimo.apache.org/xml/ns/j2ee/application-2.0"
	xmlns:ns7="http://geronimo.apache.org/xml/ns/security-2.0" 
	xmlns:ns8="http://geronimo.apache.org/xml/ns/j2ee/web-2.0.1"
	xmlns:ns9="http://java.sun.com/xml/ns/persistence"
	xmlns:ns10="http://geronimo.apache.org/xml/ns/j2ee/application-client-2.0">
	<ns2:environment>
		<ns2:moduleId>
			<ns2:groupId>default</ns2:groupId>
			<ns2:artifactId>jaxws-rest-converterclient</ns2:artifactId>
			<ns2:version>1.0</ns2:version>
			<ns2:type>car</ns2:type>
		</ns2:moduleId>

		<ns2:dependencies>
			<ns2:dependency>
				<ns2:groupId>commons-codec</ns2:groupId>
				<ns2:artifactId>commons-codec</ns2:artifactId>
				<ns2:version>1.3</ns2:version>
				<ns2:type>jar</ns2:type>
			</ns2:dependency>
			<ns2:dependency>
				<ns2:groupId>commons-httpclient</ns2:groupId>
				<ns2:artifactId>commons-httpclient</ns2:artifactId>
				<ns2:version>3.0.1</ns2:version>
				<ns2:type>jar</ns2:type>
			</ns2:dependency>
		</ns2:dependencies>
	</ns2:environment>
	<ns8:context-root>/jaxws-rest-converterclient</ns8:context-root>
</ns8:web-app>

Deploying and Testing the Web Client

Deploy

Right click on the Apache Geronimo Server Runtime present in the servers view and select Add and Remove Projects
Add jaxws-rest-converterclient to configured projects list and then click Finish
Wait for some time till the server status changes to Synchronized

Testing

Right click the index.jsp present under WebContent directory of our project and select Run As->Run On Server
In the popup, check the check box Always use this server when running the project and then click Finish
Now Eclipse will try to open the jsp in a web browser which shows you a form to enter amount in Dollars.
Enter any amount and press submit, the jsp should display the result that is returned by the web service.

The code for testing the RESTful service via POST method hasn't been added to the ConverterHandler.
A sample post file might look like this

<?xml version="1.0" encoding="UTF-8"?>
<amount dollars="23" />

This completes the development of a simple RESTful client that consumes a RESTful Web Service that is already deployed on the server.