Saturday, October 20, 2012

Build a RESTful Web service with Java

Representational state transfer (REST) is a architectural style of designing loosely coupled applications based on web-standards and the HTTP protocol. It relies on a stateless, client-server, cacheable communications protocol -- and in virtually all cases, the HTTP protocol is used.The hardest part of building a RESTful application is deciding on the resources you want to expose. Once you've done that, using the open source Restlet framework makes building RESTful Web services a snap. This tutorial guides you step-by-step through the fundamental concepts of REST and building applications with Restlets.

Step 1: Create a dynamic web project in Eclipse and add the jars shown in the figure in the lib folder under the WEB-INF



























Step 2: Add the Restful nature in the the project using fallowing entry in the web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>FirstProject</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
  <servlet-name>ServletAdaptor</servlet-name>
  <servlet-class>
   com.sun.jersey.server.impl.container.servlet.ServletAdaptor</servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>
 <servlet-mapping>
  <servlet-name>ServletAdaptor</servlet-name>
  <url-pattern>/REST/*</url-pattern>
 </servlet-mapping>
</web-app>


Step 3:Create the Employee class as fallows and annotted it with the @Path,@Produce and @Get annotations
package com.rajkrrsingh.blogspot;


import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/employee")
public class Employee {
 
 @GET
 @Produces(MediaType.TEXT_HTML)
 public String getEmployee(){
  return "<html> " + "<title>" + "Employee Details" + "</title>"
          + "<body><h1>" + "Employee Name is Dummy Employee" + "</body></h1>" + "</html> ";
 }

}

Step 4: now run the dynamic web application on the tomcat server and access the fallowing URL


http://localhost:8080/RESTfulProject/REST/employee


Here is the browser output


















Step 5:you can use jersy api or Apache HttpClient api to the test the webservice by creating a client,here I have created the client using the jersy api

package com.rajkrrsingh.blogspot.client;

import java.net.URI;

import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.UriBuilder;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;

public class Main {
 
 public static void main(String[] args) {
  ClientConfig config = new DefaultClientConfig();
     Client client = Client.create(config);
     WebResource service = client.resource(getBaseURI());
     System.out.println(service.path("REST").path("employee").accept(MediaType.TEXT_HTML).get(String.class));
  
 }
 
 private static URI getBaseURI() {
     return UriBuilder.fromUri("http://localhost:8080/RESTfulProject").build();
   }


}

After running this main class as a java application you will find the fallowing output on the console


<html> <title>Employee Details</title><body><h1>Employee Name is Dummy Employee</body></h1></html>

Post a Comment