RESTful Java Client Example Using Jersey Client

In this article i will describe how to write a JAX-RS client application using jersey client API, so far we used to call & test/read our RESTful service by its URL directly hitting in the browser [ check the previous examples ], but in the real time we will call the services by writing some client application logic.  We have different ways to write a RESTful client.  In this article i will use Jersey client [ of course we are using Jersey for writing RESTful service too 🙂 ]

Steps need to be followed

• Need to add ‘jersey-client‘ dependency in pom.xml
• As we are creating the Client application, we need to write a RESTful service to test that client, so i will take previous JSON example in order to do that
• Write a client application and run it 🙂

Files Required

• pom.xml
• web.xml
• JsonFromRestful.java
• Customer.java
• RESTfulClient.java

pom.xml

In the pom.xml we must include ‘jersey-client’ dependency [ Check line numbers from 4-10 ]

<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>JAX-RS-Client-Example</groupId>
  <artifactId>JAX-RS-Client-Example</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
 
  <repositories>
        <repository>
            <id>maven2-repository.java.net</id>
            <name>Java.net Repository for Maven</name>
            <url>http://download.java.net/maven/2/</url>
            <layout>default</layout>
        </repository>
    </repositories>
 
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.8.2</version>
            <scope>test</scope>
        </dependency>
 
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-server</artifactId>
            <version>1.8</version>
        </dependency>
        
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-json</artifactId>
            <version>1.8</version>
        </dependency>
        
        <dependency>
            <groupId>com.sun.jersey</groupId>
            <artifactId>jersey-client</artifactId>
            <version>1.8</version>
        </dependency>
        
    </dependencies>
 
      <build>
        <finalName>JAX-RS-Client-Example</finalName>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <compilerVersion>1.5</compilerVersion>
                    <source>1.5</source>
                    <target>1.5</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
 
</project>

web.xml

<?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/j2ee" xmlns:javaee="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/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" id="WebApp_ID" version="2.4">
  <display-name>JAX-RS-Client-Example</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>java4s</param-value>
        </init-param>
        <init-param>
          <param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
          <param-value>true</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>

JsonFromRestful.java

package java4s;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;

@Path("/customers")
public class JsonFromRestful {
    
    @GET
    @Path("/{cusNo}")
    @Produces("application/json")
    public Customer produceCustomerDetailsinJSON(@PathParam("cusNo") int no) {

        /*
         * I AM PASSING CUST.NO AS AN INPUT, SO WRITE SOME BACKEND RELATED STUFF AND
         * FIND THE CUSTOMER DETAILS WITH THAT ID. AND FINALLY SET THOSE RETRIEVED VALUES TO
         * THE CUSTOMER OBJECT AND RETURN IT, HOWEVER IT WILL RETURN IN JSON FORMAT :-)
         * */
        
        Customer cust = new Customer();        
            cust .setCustNo(no);
            cust .setCustName("Java4s");
            cust .setCustCountry("India");
        return cust;
    }
}

Customer.java

package java4s;

public class Customer {
    
    private int custNo;
    private String custName;
    private String custCountry;
    
    public int getCustNo() {
        return custNo;
    }
    public void setCustNo(int custNo) {
        this.custNo = custNo;
    }
    public String getCustName() {
        return custName;
    }
    public void setCustName(String custName) {
        this.custName = custName;
    }
    public String getCustCountry() {
        return custCountry;
    }
    public void setCustCountry(String custCountry) {
        this.custCountry = custCountry;
    }
    
}

RESTfulClient.java

package java4s;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class RESTfulClient {
    
    public static void main(String[] Java4s) {
        
        try {
            Client client = Client.create();    
            WebResource resource = client.resource("http://localhost:2015/JAX-RS-Client-Example/rest/customers/100");    
            ClientResponse response = resource.accept("application/json").get(ClientResponse.class);
            
            if(response.getStatus() == 200){
                
                String output = response.getEntity(String.class);
                System.out.println(output);    
                
            }else System.out.println("Somthing went wrong..!");        
    
          } catch (Exception e) {    
                  e.printStackTrace();    
          }
    
        }   
}

Explanation:

• Line number 13, we are calling our rest service
• Line number 14, we are intimating the REST Service that our client will accept JSON response
• Right click on RESTfulClient.java in eclipse > Run As > Run on Server

You Might Also Like

• Spring Boot – RESTful Web Service with POST Request in JSON Example
• Spring Boot – Example of RESTful Web Service with XML Response
• Spring Boot – Creating a RESTful Web Service Example
• Exception Handling in RESTful Web Services (JAX-RS) with Jersey
• JAX-RS Example of Multiple Resource Formats

::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.