Producing JSON Response with RESTEasy and Jackson

RESTEasy is JBOSS provided implementation of JAX-RS specification for building RESTful Web Services and RESTful Java applications. Though this is not limited to be used in JBOSS only, and you can use with other servers also.

Jackson is is a multi-purpose Java library for processing JSON data format. Jackson aims to be the best possible combination of fast, correct, lightweight, and ergonomic for developers.

In this post, I am demonstrating the way to use Jackson with RESTEasy, to convert the API response in json format.

Environment used:

1. RESTEasy 2.3.1.GA
2. RESTEasy Jackson provider 2.3.1
3. Tomcat 7
4. JDK 1.6

Follow below steps to build a demo application.

1) Create a maven project and convert to eclipse web project

mvn archetype:generate -DgroupId=com.howtodoinjava -DartifactId=RESTfulDemoApplication 
-DarchetypeArtifactId=maven-archetype-webapp -DinteractiveMode=false

mvn eclipse:eclipse -Dwtpversion=2.0

2) Update runtime dependencies in pom.xml

<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.howtodoinjava</groupId>
  <artifactId>RESTfulDemoApplication</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>RESTfulDemoApplication Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <repositories>
   	<repository>
      <id>jboss</id>
      <url>http://repository.jboss.org/maven2</url>
   	</repository>
  </repositories>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <!-- core library -->
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		 <artifactId>resteasy-jaxrs</artifactId>
		<version>2.3.1.GA</version>
	</dependency>
	<dependency>
		<groupId>net.sf.scannotation</groupId>
		<artifactId>scannotation</artifactId>
		<version>1.0.2</version>
	</dependency>
	<!-- Jackson support -->
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-jackson-provider</artifactId>
		<version>2.3.1.GA</version>
	</dependency>	
  </dependencies>
  <build>
    <finalName>RESTfulDemoApplication</finalName>
  </build>
</project>

3) Update web.xml file for resteasy specific servlet mapping

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  	<display-name>Archetype Created Web Application</display-name>
  	<!-- Auto scan REST service -->
	<context-param>
		<param-name>resteasy.scan</param-name>
		<param-value>true</param-value>
	</context-param>
	
	<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>/*</url-pattern>
	</servlet-mapping>
</web-app>

4) Write a service class and model class

User.java

package com.howtodoinjava.model;
 
import java.io.Serializable;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
 
@XmlAccessorType(XmlAccessType.NONE)
@XmlRootElement(name = "user")
public class User implements Serializable {
 
    private static final long serialVersionUID = 1L;
 
    @XmlAttribute(name = "id")
    private int id;
 
    @XmlElement(name = "firstName")
    private String firstName;
 
    @XmlElement(name = "lastName")
    private String lastName;
 
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

UserManagementModule.java

package com.howtodoinjava.service;

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

import com.howtodoinjava.model.User;

@Path("/user-management")
public class UserManagementModule
{
	@GET
	@Path("/users/{id}")
	@Produces("application/json")
	public Response getUserById(@PathParam("id") Integer id)
	{
		User user = new User();
		user.setId(id);
		user.setFirstName("Lokesh");
		user.setLastName("Gupta");
		return Response.status(200).entity(user).build();
	}
}

5) Run the application

When we deploy above built application in tomcat and hit the URL: ” http://localhost:8080/RESTfulDemoApplication/user-management/users/10″, below is the response.

Click below to download source code for this example.

Download Source code

Happy Learning !!