JSON Example With Jersey + Jackson

http://www.mkyong.com/webservices/jax-rs/json-example-with-jersey-jackson/

Jersey uses Jackson to convert object to / form JSON. In this tutorial, we show you how to convert a “Track” object into JSON format, and return it back to user.

1. Dependency

To make Jersey support JSON mapping, declares “jersey-json.jar” in Maven pom.xml file.

	<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>

Note
Review the downloaded dependencies in your project classpath, Jackson and related libraries are inlcuded.

2. Integrate JSON with Jersey

In web.xml, declares “com.sun.jersey.api.json.POJOMappingFeature” as “init-param” in Jersey mapped servlet. It will make Jersey support JSON/object mapping.

	<init-param>
		<param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
		<param-value>true</param-value>
	</init-param>

File : web.xml - full example.

<web-app ...>
 
  <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>com.mkyong.rest</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>

3. Simple Object

A simple “Track” object, later Jersey will convert it into JSON format.

package com.mkyong;
 
public class Track {
 
	String title;
	String singer;
 
	public String getTitle() {
		return title;
	}
 
	public void setTitle(String title) {
		this.title = title;
	}
 
	public String getSinger() {
		return singer;
	}
 
	public void setSinger(String singer) {
		this.singer = singer;
	}
 
	@Override
	public String toString() {
		return "Track [title=" + title + ", singer=" + singer + "]";
	}
 
}

4. JAX-RS with Jersey

Annotate the method with @Produces(MediaType.APPLICATION_JSON). Jersey will use Jackson to handle the JSON conversion automatically.

package com.mkyong.rest;
 
import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
 
import com.mkyong.Track;
 
@Path("/json/metallica")
public class JSONService {
 
	@GET
	@Path("/get")
	@Produces(MediaType.APPLICATION_JSON)
	public Track getTrackInJSON() {
 
		Track track = new Track();
		track.setTitle("Enter Sandman");
		track.setSinger("Metallica");
 
		return track;
 
	}
 
	@POST
	@Path("/post")
	@Consumes(MediaType.APPLICATION_JSON)
	public Response createTrackInJSON(Track track) {
 
		String result = "Track saved : " + track;
		return Response.status(201).entity(result).build();
 
	}
 
}

5. Demo

See demo for GET and POST request.

1. GET method
When URI pattern “/json/metallica/get” is requested, the Metallica classic song “Enter Sandman” will be returned in JSON format.

{
	"singer":"Metallica",
	"title":"Enter Sandman"
}

2. POST method
To test post request, you can create a RESTful client (refer to this Jersey client APIs example), and “post” the json format string to URI pattern “/json/metallica/post“, the posted json string will be converted into “Track” object automatically.

Download Source Code

Download it –  JSON-Support-Jersey-Example.zip (7 KB)

References

1. Jackson Official Website
2. JSON Support in Jersey