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>   

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.