Restful web services tutorial

Basics:

REST stands for Representational State Transfer.

JAX-RS is a Java programming language API for exposing the Restful web services according to the REST architecture style.

Jersey is the reference implementation of JAX-RS 311 specification.

Resource is an URI which uniquely identifies the resource.

Representation is the response provided by the resource.

For instance http://developersofjava.blogspot.in/2012/04/restful-web-services-tutorial.html is the Resource.

Representation of the resource http://developersofjava.blogspot.in/2012/04/restful-web-services-tutorial.html is in HTML which will be rendered to the browser.

Restful web services works on the HTTP methods

GET- Retrieve a representation

PUT- Modify a representation

POST- Create a representation

DELETE- Delete a representation

The REST operations can be performed only on the above methods.

Java had exposed the APIs as part of the JAX-RS 311 specification. The runtime providers must implement this specification to provide the Restful web services. The Restful web services developer is only needed to be aware of the JAX-RS standards, not necessarily the details of the runtime provider of the JAX-RS.

Hello world Restful web services with Jersey(JAX-RS 311 reference implementation):

1. Create a dynamic web project in your Java EE Eclipse IDE as shown in the below picture. 


2. Download the below shown Jersey libraries. If any of the below links did not work you can directly download them from http://jersey.java.net/
• grizzly-http-server.jar,
• grizzly-http.jar,
• grizzly-framework.jar,
• jersey-server.jar,
• jersey-grizzly2.jar,
• jersey-core.jar,
• jsr311-api.jar,
• asm.jar
• jersey-servlet
3. Place the downloaded Jersey libraries in the WEB-INF/lib directory.



4. Create HelloWorldREST.java root resource class as shown below.



package com.sai.doj.rootresources;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/helloworld")
public class HelloWorldREST {

@GET
@Produces(MediaType.TEXT_PLAIN)
public String helloWorld(){
return "Hellow world";
}

}

@path - The relative path for this root resource class. This can be specified at the method level as well.
@Produces - The type of the representation. The method helloworld produces text output. You can produce JSON,XML and HTML etc... as well.
@GET - for the get request of the resource specified with the @path annotation, the @Get annotated method will respond.

5. Configure the web.xml file as shown like below.



6. Make the web achieve and deploy into the Tomcat. For your convince i have attached the source code and war file.

HelloWorldJersey_source

HelloWorldJersy.war

The URL to access the resource that you deployed is http://localhost:8080/HelloWorldJersy/rest/helloworld


http://localhost:8080/ - Domain where the Tomcat is is installed
HelloWorldJersy - Name of the war file or display-name
rest - where our REST services are published. This is configured in web.xml
helloworld - Name of the resource, which is specified with @path in root resource class.

If you are facing any issue in making it to work, you can comment with the necessary details in this section Jersey tutorial, i am ready to help.