Hasitha's Tech Blessings

To get an basic understanding on JAX-RS, you can read [1] or JAX-RS API documentation. In the below tutorial, I will explain how to easily create a RESTful web service and a client using WSO2 Developer Studio.

Before creating a JAX-RS project,you should have setup WSO2 Developer Studio in your environment. If you are new to WSO2 Developer Studio, I recommend you to refer this link or download and setup WSO2 Developer Studio first.

Then click on the 'Developer Studio' menu in eclipse menu bar and then click on Open Dashboard. Click on 'JAX-RS Service Project' under Application Server in the dashboard. Then create a new JAX-RS Service. Enter Project, Package and Class names and click Finish. Class name should be the name of your main Service class. You may have to set Group ID, Version etc as well.

This is how my Project OrderProcessingService looks like. Note that you will have to add few external jars to your java build path such as cxf libraries, javax-ws-rs,apache-commons libraries. You may find them inside the lib folder of your WSO2 Application server distribution.

The order processing service is capable of placing orders, add items, get items etc. This is a sample code of the OrderProcessingService class.

package org.wso2.jaxrs.sample;

import javax.ws.rs.*;
import javax.ws.rs.core.Response;

@Path("/orderprocessingservice/")
public class OrderProcessingService {
 private OrderItem[] items;
 
 public OrderProcessingService() {
  items = new OrderItem[10];
   init();
 }
 
 /**
  * Add items to the list
  * 
  * @param order
  * @return
  */
 @PUT
 @Path("/items/")
 public Response addItems(OrderItem order) {
  
  OrderItem oi = new OrderItem();
  oi.setItemCode(order.getItemCode());
  oi.setQuantity(items[order.getItemCode()].getQuantity()+ order.getQuantity());
  items[order.getItemCode()]= oi;
  
  return Response.ok().build();
 
 }
 
 /**
  * Place order with item code and required quantity
  */
 @POST
 @Path("/items/")
 public Response placeOrder(OrderItem order) {
  if (items[order.getItemCode()].getQuantity() >= order.getQuantity()) {
   OrderItem oi = new OrderItem();
   oi.setItemCode(order.getItemCode());
   oi.setQuantity(items[order.getItemCode()].getQuantity()-order.getQuantity());
   items[order.getItemCode()]= oi;
   return Response.ok(oi).build();
 
  } else
   return Response.noContent().build();
 
 }
 
 /**
  * Get availability of a given item
  */
 @GET
 @Path("/items/{id}/")
 public Response getItem(@PathParam("id") int id) {
  OrderItem o = items[id];
  return Response.status(200)
    .entity(o.getItemCode() + "," + o.getQuantity()).build();
   //return Response.ok(o).build();
 }
 
 final void init() {
  OrderItem o1 = new OrderItem();
  o1.setItemCode(0);
  o1.setQuantity(20);
  items[o1.getItemCode()] = o1;
 
  OrderItem o2 = new OrderItem();
  o2.setItemCode(1);
  o2.setQuantity(50);
  items[o2.getItemCode()] = o2;
  
  OrderItem o3 = new OrderItem();
  o3.setItemCode(2);
  o3.setQuantity(70);
  items[o3.getItemCode()] = o3;
 }
 
}

package org.wso2.jaxrs.sample;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "OrderItem")
public class OrderItem {

 private int itemCode;
  private int quantity;
  
  public int getItemCode() {
   return itemCode;
  }
  public void setItemCode(int itemCode) {
   this.itemCode = itemCode;
  }
  public int getQuantity() {
   return quantity;
  }
  public void setQuantity(int quantity) {
   this.quantity = quantity;
  }
}

Test the service

package main.java.demo.jaxrs.client;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.logging.Logger;

import org.apache.cxf.helpers.IOUtils;
import org.apache.cxf.io.CachedOutputStream;
import org.apache.cxf.resource.URIResolver;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.FileRequestEntity;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.methods.PutMethod;
import org.apache.commons.httpclient.methods.RequestEntity;

public class OrderProcessingClient {

 // private static final Logger log = Logger
 // .getLogger(OrderProcessingClient.class.getName());
 private static String SERVICE_URL = "http://10.100.5.100:9763/OrderProcessingService_1.0.0/services/order_processing_service/orderprocessingservice";

 public static void main(String args[]) throws Exception {
  // setting up for sending a GET request
  System.out.println("Sending HTTP GET request to getItem.");
  URL url = new URL(SERVICE_URL + "/items/1");
  URLConnection connection = url.openConnection();
  connection.setRequestProperty("accept", "text/xml");
  InputStream in = connection.getInputStream();
  System.out.println(url.toString());
  String[] output = getStringFromInputStream(in).split(",");

  int code = Integer.parseInt(output[0]);
  int quantity = Integer.parseInt(output[1]);
  System.out.println("Item Code: " + code + "  Quantity: " + quantity);
  System.out.println("\n\nSending HTTP PUT request to addItems.");
  // get the order item xml file.
  String inputFile = OrderProcessingClient.class.getResource("Add_Items.xml").getFile();
  URIResolver resolver = new URIResolver(inputFile);
  File input = new File(resolver.getURI());
  PutMethod put = new PutMethod(SERVICE_URL + "/items");
  RequestEntity entity = new FileRequestEntity(input,"text/xml; charset=ISO-8859-1");
  put.setRequestEntity(entity);

  HttpClient httpClient = new HttpClient();
  try {
   int result = httpClient.executeMethod(put);
   System.out.println("Response status code: " + result);
   System.out.println("Response body: ");
   System.out.println(put.getResponseBodyAsString());
  } finally {
   
   put.releaseConnection();
  }

  // setting up for sending a POST request
  System.out.println("\n\nSending HTTP POST request to placeOrder.");
  //
  // get the order item xml file.
  inputFile = OrderProcessingClient.class.getResource("Place_order.xml").getFile();
  resolver = new URIResolver(inputFile);
  input = new File(resolver.getURI());
  PostMethod post = new PostMethod(SERVICE_URL + "/items");
  post.addRequestHeader("accept", "text/xml");
  entity = new FileRequestEntity(input, "text/xml; charset=ISO-8859-1");
  post.setRequestEntity(entity);
  httpClient = new HttpClient();
  try {
   int result = httpClient.executeMethod(post);
   System.out.println("Response status code: " + result);
   System.out.println("Response body: ");
   System.out.println(post.getResponseBodyAsString());
  } finally {
   
   post.releaseConnection();
  }

 }

 private static String getStringFromInputStream(InputStream in) {
  CachedOutputStream bos = new CachedOutputStream();
  try {
   IOUtils.copy(in, bos);
   in.close();
   bos.close();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

  return bos.getOut().toString();
 }
}

For POST and PUT we can use following payloads (input.xml)

Add_Items.xml

<OrderItem> <itemCode>0</itemCode> <quantity>95</quantity> </OrderItem>

Place_Order.xml

<OrderItem> <itemCode>1</itemCode> <quantity>15</quantity> </OrderItem>

POST URL:

http://10.80.85.128:9764/orderProcessingService_1.0.0/services/order_processing_service/orderprocessingservice/items/

PUT URL:

http://10.80.85.128:9764/orderProcessingService_1.0.0/services/order_processing_service/orderprocessingservice/items/

GET URL:

http://10.80.85.128:9764/orderProcessingService_1.0.0/services/order_processing_service/orderprocessingservice/items/0

ESB REST API 

Going beyond, following is a sample REST API for ESB fronting this service.

    <api xmlns="http://ws.apache.org/ns/synapse" name="testAPI" context="/esb">
        <resource methods="POST DELETE PUT GET" url-mapping="/test">
            <inSequence>
                <log level="full">
                    <property name="PPPP" value="INCOMING"></property>
                </log>
                <call>
                    <endpoint>
                        <address uri="http://10.80.85.128:9764/orderProcessingService_1.0.0/services/order_processing_service/orderprocessingservice/items/0 format=rest"></address>
                    </endpoint>
                </call>
                <log level="full">
                    <property name="PPPP" value="PPPP"></property>
                </log>
            </inSequence>
            <outSequence>
                <log level="full"></log>
                <send></send>
            </outSequence>
        </resource>
    </api>