Consuming a RESTful webservice with JAX-RS Client API

In this tutorial we’ll use the JAX-RS Client API to consume the sample RESTfull web service created in the previous tutorial on Creating and deploying RESTful Web Services with JAX-RS .

The JAX-RS Client API provides a high-level API for accessing any REST resources, not just JAX-RS services. The Client API is defined in the javax.ws.rs.clientpackage . We’ll use it to consume the HelloResource sample of restfull webservice created in previous tutorial as follows:

1. Create and configure a new maven project ( adding jaxrs and resteasy client apis dependencies to pom file )

    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" >
      <modelVersion >4.0.0 </modelVersion>
      <groupId>net.pragmatictheories.restsamples </groupId>
      <artifactId>HelloRESTClient </artifactId>
      <version>0.0.1-SNAPSHOT </version>
     
     <properties>
     <maven.compiler.source>1.8</maven.compiler.source>
     <maven.compiler.target>1.8</maven.compiler.target>
     </properties>
     
     <dependencies>
   <!--  jaxrs -- >
     <dependency>
               <groupId>javax.ws.rs</groupId>
               <artifactId>javax.ws.rs-api</artifactId>
               <version>2.0</version>
     </dependency>
     <!--  resteasy -- >
     <dependency >
       <groupId&gtorg.jboss.resteasy</groupId >
       <artifactId&gtresteasy-client</artifactId >
       <version&gt3.0.2.Final</version >
    </dependency >
      
       </dependencies >
   </project >
   

2. Add a new HelloRestClient java class with a main included where you’ll create a new JAX-RS client, define a webTarget using the base url of the webservice and consume it as follows:

   public class HelloResourceClient {
   
   	public static void main(String[] args) {
   
   		// create new JAX-RS client
   		Client client = ClientBuilder.newClient();
   
   		// the base url of the service
   		WebTarget target = client.target("http://localhost:18080/HelloREST/rest");
   
   		// consuming sayHello method
   		WebTarget hello = target.path("hello");
   
   		// get the response from the target url
   		Response response = hello.request().get();
   
   		// read the result as a string
   		String result = response.readEntity(String.class);
   
   		System.out.println("sayHello method returned: " + result);
   		response.close();
   
   		/*********** Consuming a rest resource with parameters ********/
   		/*** identified by a url ***/
   
   		// Building the relative URL manually for the sayHelloTo method
                   WebTarget helloTo1 = target.path("hello").path("sayHelloTo").path("p1").path("p2");
   		Response response1 = helloTo1.request().get();
   		String result1 = response1.readEntity(String.class);
   		System.out.println("sayHelloTo with path params returned: " + result1);
   		response1.close();
   
   		/*** accessible via a url ***/
   		// building the relative URL manually for the sayHelloSecond method
   		WebTarget helloTo2 = target.path("hello").path("sayHelloToSecond").queryParam("p1", "amal").queryParam("p2",
   				"another amal");
   		// get the response from the target url
   		Response response2 = helloTo2.request().get();
   		// read the result as a string
   		String result2 = response2.readEntity(String.class);
   		// print the result to the standard output
   		System.out.println("sayHelloTo with query params returned: " + result2);
   		response2.close();
   
   		// close client after consuming resources
   		client.close();
   	}
   
   }

That’s all folks ! This might be the easiest tutorial on what consuming a restfull webservice is ! The following video is a quick demo on how to build the maven project and consume your rest resource: