RESTful WS using Jersey Part 1 - Hello World

Here is the simple tutorial for RESTful Web Service using jersey implementation for RESTful Web Services. Java EE 6 has introduced jersey API as implementation for JSR-311 as API for RESTful Web Services. For ease of development,deployment and testing i have used NetBean 6.8 which supports JEE 6.

Jersey is an annotation based implementation. Here are the few important annotations used in this tutorial

@path(“/path/”) - a relative URI path indicating where the Java class will
be hosted

@GET - a request method designator and corresponds to HTTP Get method

@POST - a request method designator and corresponds to HTTP Post method

@Produces("text/plain") - specify the MIME media types of representations
a resource can produce

@Consumes("text/plain") -specify the MIME media types of representations
a resource can consume

@PathParam("User_Name") - a type of parameter that you can extract for use in your
resource class

@QueryParam("surname") - a type of parameter that you can extract from url query for use in your recourse class.

In Restful Web Services, each implementation is a resource and we can access its representational state using Get, Post, Put and Delete operations. Here we have implemented Get and Post operations.

In this post i am going to demo developing, deploying and testing RESTful services using Jersey APIs in Netbean 6.8

1. Create a Java Web Application

2. Specify Context path at end of this wazard

At the end of this wizard, you will find a standard web application structure under project

3. Create a web.xml file if NetBean didn’t create it

This wizard creates empty standard web.xml file under WEB-INF. Update this file with Jersey default adaptor for restful services

<servlet>
        <servlet-name>ServletAdaptor</servlet-name>
        <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>ServletAdaptor</servlet-name>
        <url-pattern>/resources/*</url-pattern>
    </servlet-mapping>

updating this mapping file in web.xml , we are telling web application to route all url requests with given format (/resources/*) to ServletContainer. This servlet will take care of handling all available resources.

4. Create Restful Web Service using wizard

Mention all required info during this wizard

Here resource package name, path ,MIME type and resource name has been defined. Path’s value will appear to resource class file as annotations. MIME type will define type response/request generated/accepted by this service. This info will also appear as annotations.

5. After all this steps complete project will be like

6. Updating Resource class – modify get method so that it will return a string on invoke. Here is the complete code for resource class

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/

package demo.resorces;

import javax.ws.rs.core.Context;
import javax.ws.rs.core.UriInfo;
import javax.ws.rs.PathParam;
import javax.ws.rs.Consumes;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.GET;
import javax.ws.rs.Produces;

/**
* REST Web Service
*
* @author Yogesh
*/

@Path("hello")
public class HelloResource {
    @Context
    private UriInfo context;

    /** Creates a new instance of HelloResource */
    public HelloResource() {
    }

    /**
     * Retrieves representation of an instance of demo.resorces.HelloResource
     * @return an instance of java.lang.String
     */
    @GET
    @Produces("text/plain")
    public String getText() {
        //TODO return proper representation object
        return "Hello from GetText";
    }

    /**
     * PUT method for updating or creating an instance of HelloResource
     * @param content representation for the resource
     * @return an HTTP response with content of the updated or created resource.
     */
    @PUT
    @Consumes("text/plain")
    public void putText(String content) {
    }
}

Here getText method is annotated with @Get and @Produces tags , it means it will get invoked on HTTP Get request and produces simple plain text.

7. Running Project - To deploy and test this service we need update project properties so that on running this project it will launch appropriate url

8. Right click on project and run , you will see output as shown in below

9. Now modify getText method to produce html output instead of plain text.

@GET
   //@Produces("text/plain")
   @Produces("text/html")
   public String getText() {
       //TODO return proper representation object
       //return "Hello from GetText";
       return "<html><body><h1>Hello from GetHtml</h1></body></html>";
   }

10. After running project with updated getText method

Here we got html output.