Restful Webservice Example In Eclipse

What is RESTful webservice?

REST stands for REpresentational State Transfer. REST is an architectural style and gaining popularity over SOAP webservices. Below are the REST fundamentals

• Everything in REST is considered as resource and every resource is identified by URI
• All resources are handled by GET, POST, PUT, DELETE operations
• Every request is independent request hence it is stateless.
• Communication is done via representations e.g. JSON, XML over HTTP protocol.

Objective

The objectives of this blog are

• understand how to write a RESTful webproject with Jersey framework.
• Deploy the project in tomcat server
• Access the webservice

Requeired Software

• JDK 1.7
• Eclipse for J2EE
• Maven 2.2.x or above

Stepts to write code

Below are the steps to write a simple RESTful webservice

• Create a Dynamic web project with module version 3.0 and java source directory must be src/main/java
• Convert the project into maven project (right click on project-> Configure -> Convert to Maven project)
• Create a package under java source (src/main/java): com.ashish.rest.controller
• Add maven dependancy: Right click on project->properties->Deployment Assembly->Add->Java Build Path Entries->Maven Dependencies Note: Deploy path should be WEB-INF/lib by default The meaning of the below entry (as shown in the image) is that the dependent jars will get packaged into the WEB-INF/lib folder of the deployer

• Your pom.xml file should be as shown below

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.ashish.rest.controller</groupId>
	<artifactId>RestfulWebservice</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<repositories>
		<repository>
			<id>maven2-repository.java.net</id>
			<name>Java.net Repository for Maven</name>
			<url>http://download.java.net/maven/2/</url>
			<layout>default</layout>
		</repository>
	</repositories>

	<dependencies>
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-server</artifactId>
			<version>1.9</version>
		</dependency>

		<!-- Below two dependencies are added to support JSON response -->
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-json</artifactId>
			<version>1.8</version>
		</dependency>
		<dependency>
			<groupId>com.sun.jersey</groupId>
			<artifactId>jersey-bundle</artifactId>
			<version>1.18.1</version>
		</dependency>
	</dependencies>

</project>

• Your web.xml should be as shown below. As per the web.xml file http://server://rest/* request will pass through the controller. Go through the inline comments 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"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
	id="WebApp_ID" version="3.0">
	<display-name>Restful WebApplication</display-name>

	<servlet>
		<servlet-name>jersey-helloWorld-serlvet</servlet-name>
		<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
		<!-- Below init-param is added to for RESTful webservice with Jersey framework -->
		<init-param>
			<param-name>com.sun.jersey.config.property.packages</param-name>
			<param-value>com.ashish.rest.controller</param-value>
		</init-param>

		<!-- Below init-param is added to support JSON response -->
		<init-param>
			<param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
			<param-value>true</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>jersey-helloWorld-serlvet</servlet-name>
		<url-pattern>/rest/*</url-pattern>
	</servlet-mapping>
</web-app>

• Your controller class HelloWorldREST.java should be as shown below. This controller produces string output and json output.

package com.ashish.rest.controller;

import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import com.ashish.rest.bean.Employee;

@Path("/hello")
public class HelloWorldREST {
	@GET
	@Path("/{parameter}")
	public Response responseMsg( @PathParam("parameter") String parameter,
			@DefaultValue("Nothing to say") @QueryParam("value") String value) {
		String output = "Hello from: " + parameter + " : " + value;
		return Response.status(200).entity(output).build();
	}
	
	@GET
	@Path("/getEmployee/{empId}")
	@Produces(MediaType.APPLICATION_JSON)
	public Employee getEmployee( @PathParam("empId") int empId,
			@DefaultValue("No Employee Id passed") @QueryParam("value") String value) {

		Employee emp = new Employee();
		emp.setEmpId(empId);
		emp.setName("Ashish Mondal");

		return emp;
	}
	
	@POST
	@Path("/getSalary")
	@Produces(MediaType.APPLICATION_JSON)
	public Employee getSalary( @PathParam("empId") int empId,
			@DefaultValue("No Employee Id passed") @QueryParam("value") String value) {
		System.out.println("getSalary method is called");
		Employee emp = new Employee();
		emp.setEmpId(empId);
		emp.setName("Ashish Mondal");
		emp.setSalary(1000);
		return emp;
	}
}

• Right click on the project then Run As-> Run on Server
• 1st request and response from the above controller is shown in the below image
• 2nd request and response from the above controller is shown in the below image

Note: In the above controller class, getSalary resource can be called by POST and GET methods. The GET method is shown above. I am going to show the POST method below.

• Note that index.jsp is mentioned as the welcome file in web.xml.
• Create index.jsp file under WebContent folder and the content should be as shown below

<%@ 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>Insert title here</title>
</head>
<body>
	<form method="post" action="rest/hello/getSalary/">
		<div>POST method testing</div>
		<div>
			Emp Id: <input type="text" value="" />
			<button>Go</button>
		</div>
	</form>
</body>
</html>

• Follow the below steps to test the POST request from webpage

Common issues during project setup