JAX-RS Jersey Hello World Example

In this tutorial, we will create a simple hello world web service with the JAX-RS reference implementation Jersey, which is the reference implementation of the JSR 311 specification.JAX-RS is part of the Java EE.  REST (REpresentational State Transfer) is a simple stateless architecture that generally runs over HTTP. Now let’s see create our first JAX-RS service

 Folder Structure :

1. Create a Dynamic Web Project RestfulExample and create a package for our src files “com.javainterviewpoint“
2. Place the required jar files under WEB-INF/Lib 
   

   jersey-bundle-1.18.jar
   asm-3.1.jar

3. Create the Java classes HelloWorld.java under com.javainterviewpoint folder.
4. Place the web.xml  under the WEB-INF directory

HelloWorld.java

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Response;

@Path("/hello")
public class HelloWorld 
{
	@GET
	@Path("/{param}")
	public Response dispMessage(@PathParam("param")String msg )
	{	
		String output = "Welcome to RESTful Jersey example - "+msg;
		return Response.status(200).entity(output).build();
	}
}

• We have annotated @Path(“/hello”) at the class level, which means our HelloWorld service can be reached through the URL …/hello
• All the GET Request will be handled by the dispMessage() method, which we have annotated with @GET
• @Path(“/{param}”) will hold the value which will be passed in the URL after ../hello/XXXX, Using the @PathParam we will get the value of the “param” and will be assigned to String msg.
• Finally, we will send our Response back.

web.xml

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://java.sun.com/xml/ns/j2ee" 
xmlns:web="http://xmlns.jcp.org/xml/ns/javaee" 
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee	
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd	http://java.sun.com/xml/ns/j2ee	
http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
 
 	<display-name>Restful Web Application</display-name>
	<servlet>
	 	<servlet-name>jersey-serlvet</servlet-name>
	 	<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
	 	<init-param>
	 		<param-name>com.sun.jersey.config.property.packages</param-name>
		 	<param-value>com.javainterviewpoint</param-value>
	 	</init-param>
	 	<load-on-startup>1</load-on-startup>
	</servlet>
 	<servlet-mapping>
	 	<servlet-name>jersey-serlvet</servlet-name>
	 	<url-pattern>/rest/*</url-pattern>
 	</servlet-mapping>
</web-app>

In web.xml, we have to register “com.sun.jersey.spi.container.servlet.ServletContainer“, and mention your  source folder under init-param, “com.sun.jersey.config.property.packages“ so that Jersey will look for the web service classes under the package mentioned.

Lets run our application

Now are good to run our application, add the project to the server. I use Tomcat as my server you are free to choose your own.
        http://localhost:8080/RestfulExample/rest/hello/<<parameter passed>>

The request url has to match http://<<server location>>:<<port>>/<<url-pattern if any>>/<<Path mentioned in java @Path>>/{any value}