RESTful Java client with RESTEasy client

Previously we have learnt how to create a RESTful Web Service using RESTEasy api. In this RESTEasy client tutorial we will learn how to Consume REST Web Service using RESTEasy client.

Folder Structure :

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

   resteasy-jaxrs-3.0.4.Final.jar
   jaxrs-api-3.0.4.Final.jar
   resteasy-jackson-provider-3.0.4.Final.jar
   resteasy-jaxb-provider-3.0.4.Final.jar
   resteasy-jettison-provider-3.0.4.Final.jar
   commons-io-2.4.jar
   commons-logging-1.2.jar
   httpclient-4.5.2.jar
   httpcore-4.4.4.jar
   javassist-3.20.0-GA.jar
   scannotation-1.0.2.jar
   jboss-logging-3.3.0.Final.jar

3. Create the Java classes Student.java,StudentRESTService.java and StudentRESTEasyClient.java under  com.javainterviewpoint folder.
4. Place the web.xml  under the WEB-INF directory

Student.java

Student class is our model class,we have annotated our Student class with @XmlRootElement marking the root element.

package com.javainterviewpoint;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Student 
{
    private String name;
    private int age;
       
    public Student() {
    }
    
    public Student(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

   public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

web.xml

<web-app id="WebApp_ID" version="2.4"
	xmlns="http://java.sun.com/xml/ns/j2ee"	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee	
 	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
	<display-name>RESTEasy Restful Web Application</display-name>

	<servlet>
		<servlet-name>resteasy-servlet</servlet-name>
		<servlet-class>
			org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher
		</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>resteasy-servlet</servlet-name>
		<url-pattern>/rest/*</url-pattern>
	</servlet-mapping>

	<!-- Auto scanning REST service -->
	<context-param>
		<param-name>resteasy.scan</param-name>
		<param-value>true</param-value>
	</context-param>

	<!-- Prefix need to be set if url pattern is not /* -->
	<context-param>
		<param-name>resteasy.servlet.mapping.prefix</param-name>
		<param-value>/rest</param-value>
	</context-param>

	<listener>
		<listener-class>
			org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap
		</listener-class>
	</listener>

</web-app>

• In our “web.xml” file, we have registered “org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher” as our servlet container
• We have also registered a listener “org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap”.
• The ResteasyBootstrap listener is responsible for initializing the basic components of RESTeasy as well as scanning for annotation classes. It also reads the configuration options from <context-param> elements of the “web.xml” file.
• The configuration prefix must be set if the url-pattern of the <servlet-mapping> is not “/*”.  This will be taken care by “resteasy.servlet.mapping.prefix”, the value provided should same as the url-pattern of the servlet-mapping except “/*”. In our case we have url-pattern as “/rest/*” and hence the “resteasy.servlet.mapping.prefix” value should be “/rest”
• One more configuration is added “resteasy.scan”, when this values is set to “true”, this will tell ResteasyBootstrap to automatically search for REST Services Implementation, both @Provider and JAX-RS resource classes (@Path, @GET, @POST etc…) and register them.

RESTEasy client GET example

REST Service for GET – HTTP method

StudentService.java

package com.javainterviewpoint;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
@Path("/student")
public class StudentRESTService 
{   
    @GET
    @Path("/getJSONStudent")
    @Produces("application/json")
    public Student getStudentJSONResponse()
    {
        Student s = new Student();
        s.setAge(99);
        s.setName("JavaInterviewPoint11");
        return s;
    }
    @GET
    @Path("/getXMLStudent")
    @Produces("application/xml")
    public Student getStudentXmlResponse()
    {
        Student s = new Student();
        s.setAge(22);
        s.setName("JavaInterviewPoint22");
        return s;
    }
}

• Our RESTful Web Service has two methods getStudentJSONResponse() and getStudentXmlResponse(), first method produces the JSON response and the later produces XML Response which can be consumed by the RESTEasy Java Client.
• @GET being idempotent we have annotated it on top of each methods.
• @Produces annotation confirms the output format which will be produced by each method.

StudentRESTEasyClient.java

package com.javainterviewpoint;

import org.jboss.resteasy.client.ClientRequest;
import org.jboss.resteasy.client.ClientResponse;

public class StudentRESTEasyClient
{
    public static void main(String[] args)
    {
        try
        {
            //ClientRequest - Hits our REST Service
            ClientRequest request = new ClientRequest("http://localhost:8080/RESTEasyTutorial/rest/student/getJSONStudent");
            
            //Setting the accepted response format
            request.accept("application/json");
             
            //Obtaining the client response
            ClientResponse response = request.get(Student.class);
             
            //Validate the response status code
            if(response.getResponseStatus().getStatusCode() != 200)
            {
                throw new RuntimeException("Failed with HTTP error code : " 
                       + response.getResponseStatus().getStatusCode());
            }
             
            //Retrieve the Student from the entity
            Student st = response.getEntity();
             
            //Printing the elements of Student
            System.out.println("Student Name : "+st.getName());
            System.out.println("Student Age  : "+st.getAge());

        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

We will be performing the below operations

1. Create a ClientRequest object which hits our RESTful WebService.
2. On the ClientRequest object created, set the accepted response format.
3. ClientResponse holds the reponse received from our service
4. Validate the response code of the received response.

Output : 

Student Name : JavaInterviewPoint11
Student Age : 99

RESTEasy client POST example

REST Service for POST – HTTP method

StudentService.java

package com.javainterviewpoint;

import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.core.Response;
@Path("/student")
public class StudentRESTService 
{   
    @POST
    @Path("/postJSONStudent")
    @Consumes("application/json")
    public Response postStudentJSONInput(Student st)
    {
        String result = "Student Received  \nStudent Name : "+st.getName()
            +" \nStudent Age : "+st.getAge();
        return Response.status(201).entity(result).build();
    }
    @POST
    @Path("/postXMLStudent")
    @Consumes("application/xml")
    public Response postStudentXmlInput(Student st)
    {
        String result = "Student Received  \nStudent Name : "+st.getName()
        +" \nStudent Age : "+st.getAge();
        return Response.status(201).entity(result).build();
    }
}

• Our POST RESTful Web Service has two methods postStudentJSONInput() and postStudentXmlInput(), first method  consumes the JSON input and the later consumes XML input.
• Since @POST is non idempotent we have annotated it on top of each methods.
• @Consumes annotation tells us the input format acceptable by each methods.

StudentRESTEasyClient.java

package com.javainterviewpoint;

import org.jboss.resteasy.client.ClientRequest;
import org.jboss.resteasy.client.ClientResponse;

public class StudentRESTEasyClient
{
    public static void main(String[] args)
    {
        try
        {
            //ClientRequest - Hits our REST Service
            ClientRequest request = new ClientRequest("http://localhost:8080/RESTEasyTutorial/rest/student/postJSONStudent");
            
            //Setting the accepted response format
            String input = "{\"student\": {\"age\": 999,\"name\": \"JavaInterviewPoint999\"}}";
            request.body("application/json", input);
             
            //Obtaining the client response
            ClientResponse response = request.post(String.class);
             
            //Validating the response status code
            if(response.getResponseStatus().getStatusCode() != 201)
            {
                throw new RuntimeException("Failed with HTTP error code : " 
                        + response.getResponseStatus().getStatusCode());
            }
             
            //Retrieve the Student from the entity
            System.out.println(response.getEntity());

        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

Output :

Student Received  
Student Name : JavaInterviewPoint999 
Student Age : 999