rest helloworld

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RESTful WS using Jersey: "Hello world!"

JAX-RS is a java specification which define APIs to implement RESTful web services. Jersey is a reference implementation of JAX-RS. It provides libraries to develop RESTful web services based on the JAX-RS specification. It uses a servlet to receive and dispatch client requests to right execution classes. In this tutorial, we will develop a simple service which returns string “Hello world!” to client using Jersey.

Prerequisites

Eclipse Java EE.
Tomcat server.
Jersey library.

Step 1: setting up Tomcat on Eclipse

Refer to this tutorial.

Step 2: Create your project

Open Eclipse, File→New→Dynamic Web Project.
Name the project: rest. Select Target runtime as your Apache Tomcat. Click Finish.
Download and extract the Jersey package.
Copy jersey-server.jar , jersey-core.jar, jersey-servlet.jar and asm.jar to the WebContent→WEB-INF→lib folder.
Create new package in the src folder. Name it: my.first.rest.
Create new Java class inside this package. Name it: Hello.

Edit it as following:

package my.first.rest; import javax.ws.rs.GET;import javax.ws.rs.Path;import javax.ws.rs.Produces;import javax.ws.rs.core.MediaType; @Path("hello")public class Hello {   // This method is called if TEXT_PLAIN is requested  @GET  @Produces(MediaType.TEXT_PLAIN)  public String sayHelloInPlainText() {      return "Hello world!";  }   // This method is called if HTML is requested  @GET  @Produces(MediaType.TEXT_HTML)  public String sayHelloInHtml() {    return "<html> " + "<title>" + "Hello world!" + "</title>"        + "<body><h1>" + "Hello world!" + "</body></h1>" + "</html> ";  }}

Step 3: Define the servlet container

Create a file: web.xml in the WebContent→WEB-INF folder.

Insert the following code into the web.xml file:

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">   <display-name>rest</display-name>   <servlet>    <servlet-name>Jersey REST Service</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>my.first.rest</param-value>    </init-param>    <load-on-startup>1</load-on-startup>  </servlet>   <servlet-mapping>    <servlet-name>Jersey REST Service</servlet-name>    <url-pattern>/*</url-pattern>  </servlet-mapping> </web-app>

Note that:
1. <param-value> is your package's name.
2. the URL of your service will be: http://your_domain:port/<project-name>/<url-pattern>/<path_from_rest_class>. In this example, this URL is: http://localhost:8080/rest/hello (<project-name> is rest, <url-pattern> is empty, <path_from_rest_class> is hello as declared in step 2).

Step 4: Publish and check your service

Start the Tomcat server
Right click on Tomcat server→Add and Remove…. Select the rest project.
Verify the response in HTML by your browser: http://localhost:8080/rest/hello.
Verify the response in PLAINTEXT using command curl: open your terminal and type: curl http://localhost:8080/rest/hello

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