RESTful with RESTEasy - Part 2/4 (Client Consuming a POST and GET RESTful Service)

Overview:
This post looks at how to write a service client using RESTEasy framework, which is an excellent framework for developing RESTful services, and has gained a lot of popularity in the Mobile application development world.

Also Refer to,
RESTful with RESTEasy - Part 1/4 (Creating a POST and GET RESTful Service)

You can find the sample code here.

Prerequisite:JDK >= 1.5.x

Maven >= 2.2.x

Step 1: Maven Dependencies (pom.xml)
Update your client project's pom.xml by adding the following RESTEasy dependency.

 <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/maven-v4_0_0.xsd">  
   . . .
   <dependencies>  
     . . .  
     <dependency>  
       <groupId>org.jboss.resteasy</groupId>  
       <artifactId>resteasy-jaxrs</artifactId>  
       <version>${resteasy.version}</version>  
     </dependency>  
    . . .
   </dependencies>  
   . . .
 </project>  

Step 2: How to create a requests

   private static final String SERVICE_URL = "http://localhost:8080/greetingspring";  
   private static final String SERVICE_URL_ADD = "/add";  
   private static final String SERVICE_URL_UPDATED = "/update";  
   private static final String SERVICE_URL_GET = "/get/{id}";  
   private static final String SERVICE_URL_GET_ALL = "/getAll";  
   . . .  
   private static ClientRequest createRequest(String uri) {  
     ClientRequest request = new ClientRequest(SERVICE_URL + uri);  
     request.accept("application/json");  
     return request;  
   }  
   . . .  
   ClientRequest request = createRequest(SERVICE_URL_ADD)  
   ClientRequest request = createRequest(SERVICE_URL_GET)  
   ClientRequest request = createRequest(SERVICE_URL_UPDATE)  
   ClientRequest request = createRequest(SERVICE_URL_GET_ALL)  

Creating a POST request

 private static Long addUser(User newUser) throws Exception {  
     String requestJson = "{\"user\":" + JSON_CONVERTER.toJson(newUser) + "}";  
     displayRequest(requestJson);  
     ClientRequest request = createRequest(SERVICE_URL_ADD).body(CONTENT_TYPE, requestJson);  
     ClientResponse<String> response = request.post(String.class);  
     displayResponse(response, HTTP_CODE_CREATED);  
     return Long.parseLong(response.getEntity().toString());  
   }  

Creating a GET request

 private static User getUser(Long userId) throws Exception {  
     ClientRequest request = createRequest(SERVICE_URL_GET.replace("{id}", userId.toString()));  
     ClientResponse<String> response = request.get(String.class);  
     displayResponse(response, HTTP_CODE_OK);  
     String responseJson = response.getEntity().toString();  
     responseJson = responseJson.replace("{\"user\":", "").replace("}}", "}");  
     return JSON_CONVERTER.fromJson(responseJson, User.class);  
   }  

Complete Code for the Client

 package org.fazlan.resteasy.spring.client;  
 import com.google.gson.Gson;  
 import org.fazlan.resteasy.spring.entity.User;  
 import org.jboss.resteasy.client.ClientRequest;  
 import org.jboss.resteasy.client.ClientResponse;  
 import java.io.BufferedReader;  
 import java.io.ByteArrayInputStream;  
 import java.io.IOException;  
 import java.io.InputStreamReader;  

 public class RestClient {  

   private static final String SERVICE_URL = "http://localhost:8080/greetingspring";  
   private static final String SERVICE_URL_ADD = "/add";  
   private static final String SERVICE_URL_UPDATED = "/update";  
   private static final String SERVICE_URL_GET = "/get/{id}";  
   private static final String SERVICE_URL_GET_ALL = "/getAll";  
   private static final String CONTENT_TYPE = "application/json";  
   private static final Gson JSON_CONVERTER = new Gson();  
   private static final int HTTP_CODE_OK = 200;  
   private static final int HTTP_CODE_CREATED = 201;  

   public static void main(String[] args) throws Exception {  
     User newUser = new User("Firstname", "Lastname");  
     Long userId = addUser(newUser);  
     User user = getUser(userId);  
     displayUser(user);  
     user.setFirstName("Updated " + user.getFirstName());  
     userId = updateUser(user);  
     user = getUser(userId);  
     displayUser(user);  
     addUser( new User("AnotherFirstName", "AnotherLastName"));  
     getAllUsers();  
   }  
   private static Long addUser(User newUser) throws Exception {  
     String requestJson = "{\"user\":" + JSON_CONVERTER.toJson(newUser) + "}";  
     displayRequest(requestJson);  
     ClientRequest request = createRequest(SERVICE_URL_ADD).body(CONTENT_TYPE, requestJson);  
     ClientResponse<String> response = request.post(String.class);  
     displayResponse(response, HTTP_CODE_CREATED);  
     return Long.parseLong(response.getEntity().toString());  
   }  
   private static Long updateUser(User user) throws Exception {  
     String requestJson = "{\"user\":" + JSON_CONVERTER.toJson(user) + "}";  
     displayRequest(requestJson);  
     ClientRequest request = createRequest(SERVICE_URL_UPDATED).body(CONTENT_TYPE, requestJson);  
     ClientResponse<String> response = request.post(String.class);  
     displayResponse(response, HTTP_CODE_OK);  
     return Long.parseLong(response.getEntity().toString());  
   }  
   private static User getUser(Long userId) throws Exception {  
     ClientRequest request = createRequest(SERVICE_URL_GET.replace("{id}", userId.toString()));  
     ClientResponse<String> response = request.get(String.class);  
     displayResponse(response, HTTP_CODE_OK);  
     String responseJson = response.getEntity().toString();  
     responseJson = responseJson.replace("{\"user\":", "").replace("}}", "}");  
     return JSON_CONVERTER.fromJson(responseJson, User.class);  
   }  
   private static void getAllUsers() throws Exception {  
     ClientRequest request = createRequest(SERVICE_URL_GET_ALL);  
     ClientResponse<String> response = request.get(String.class);  
     displayResponse(response, HTTP_CODE_OK);  
   }  
   private static ClientRequest createRequest(String uri) {  
     ClientRequest request = new ClientRequest(SERVICE_URL + uri);  
     request.accept("application/json");  
     return request;  
   }  
   private static void displayUser(User user) {  
     System.out.println(user);  
   }  
   private static void displayRequest(String request) {  
     System.out.println(request);  
   }  
   private static void displayResponse(ClientResponse<String> response, int expectedResponseCode) throws IOException {  
     if (response.getStatus() != expectedResponseCode) {  
       throw new RuntimeException("Failed : HTTP error code : " + response.getStatus());  
     }  
     BufferedReader br = new BufferedReader(new InputStreamReader(  
         new ByteArrayInputStream(response.getEntity().getBytes())));  
     String output;  
     System.out.println("Output from Server .... \n");  
     while ((output = br.readLine()) != null) {  
       System.out.println(output);  
     }  
   }  
 }  

Summary:
This tutorial looked at how we can consume RESTful Web Service using RESTEasy.

You can find the sample code here.