RESTful Web Service with Java: Tutorial

RESTful Web Services

This post will demonstrate how to create a RESTful Web Service and client using Jersey framework which extends JAX-RS API.

REST fundamentals

• Everything in REST is considered as a resource.
• Every resource is identified by an URI.
• Uses uniform interfaces. Resources are handled using POST, GET, PUT, DELETE operations which are similar to Create, Read, update and Delete(CRUD) operations.
• Be stateless. Every request is an independent request. Each request from client to server must contain all the information necessary to understand the request.
• Communications are done via representations. E.g. XML, JSON.

Download Jersey zip bundle from here.

You will need these jars:

asm-3.1.jar

jersey-client-1.17.1.jar

jersey-core-1.17.1.jar

jersey-server-1.17.1.jar

jersey-servlet-1.17.1.jar

jsr311-api-1.1.1.jar

Now create a new class UserInfo.java.

package com.restws;

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

@Path("UserInfoService")
public class UserInfo {

 @GET
 @Path("/name/{i}")
 @Produces(MediaType.TEXT_XML)
 public String userName(@PathParam("i") String i){
  
  String name = i;
  return "" + "" + name + "" + "";
  
 }

 @GET
 @Path("/age/{j}")
 @Produces(MediaType.TEXT_XML)
 public String userAge(@PathParam("j") int j){
  
  int age = j;
  return "" + "" + age + "" + "";
  
 }

Now create web.xml file in WEb-INF folder.

}

To run the project, right click on it and click on run as ->run on server.

http://localhost:8080/RESTfulWS/rest/UserInfoService/name/Akash

Now create MyClient.java:

package com.restclient;

import javax.ws.rs.core.MediaType;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
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 MyClient {

  public static final String BaseURI = "http://localhost:8080/RESTfulWS";
 public static final String PATH_NAME = "/MyService/name/";
 public static final String PATH_AGE = "/MyService/age/";

  public static void main(String... args) {

   String name = "Akash";
  int age = 26;

   ClientConfig config = new DefaultClientConfig();
  Client client = Client.create(config);
  WebResource resource = client.resource(BaseURI);

   WebResource nameResource = resource.path("rest").path(PATH_NAME + name);
  System.out.println("Client Response \n"
    + getClientResponse(nameResource));
  System.out.println("Response \n" + getResponse(nameResource) + "\n\n");

   WebResource ageResource = resource.path("rest").path(PATH_AGE + age);
  System.out.println("Client Response \n"
    + getClientResponse(ageResource));
  System.out.println("Response \n" + getResponse(ageResource));
 }

  /* Returns client response */
 private static String getClientResponse(WebResource resource) {
  return resource.accept(MediaType.TEXT_XML).get(ClientResponse.class)
    .toString();
 }

  /* Returns the response as XML */
 private static String getResponse(WebResource resource) {
  return resource.accept(MediaType.TEXT_XML).get(String.class);
 }
}

Run MyClient.java as Java applicaiton, you will get following output:

Client Response
GET http://localhost:8080/RESTfulWS/rest/MyService/name/Akash returned a response status of 200 OK
Response
Akash

Client Response
GET http://localhost:8080/RESTfulWS/rest/MyService/age/26 returned a response status of 200 OK
Response
26