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.
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.
File : web.xml - full example.
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.
RESTful Java client with Jersey client
This tutorial show you how to use Jersey client APIs to create a RESTful Java client to perform “GET” and “POST” requests to REST service that created in this “Jersey + Json” example.
1. Jersey Client Dependency
To use Jersey client APIs, declares “jersey-client.jar” in your pom.xml file.
File : pom.xml
2. GET Request
Review last REST service.
@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;
}
//...
Jersey client to send a “GET” request and print out the returned json data.
package com.mkyong.client;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
public class JerseyClientGet {
public static void main(String[] args) {
try {
Client client = Client.create();
WebResource webResource = client
.resource("http://localhost:8080/RESTfulExample/rest/json/metallica/get");
ClientResponse response = webResource.accept("application/json")
.get(ClientResponse.class);
if (response.getStatus() != 200) {
throw new RuntimeException("Failed : HTTP error code : "
+ response.getStatus());
}
String output = response.getEntity(String.class);
System.out.println("Output from Server .... \n");
System.out.println(output);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output…
Output from Server ....
{"singer":"Metallica","title":"Enter Sandman"}
3. POST Request
Review last REST service.
@Path("/json/metallica")
public class JSONService {
@POST
@Path("/post")
@Consumes(MediaType.APPLICATION_JSON)
public Response createTrackInJSON(Track track) {
String result = "Track saved : " + track;
return Response.status(201).entity(result).build();
}
//...
Jersey client to send a “POST” request, with json data and print out the returned output.
package com.mkyong.client;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
public class JerseyClientPost {
public static void main(String[] args) {
try {
Client client = Client.create();
WebResource webResource = client
.resource("http://localhost:8080/RESTfulExample/rest/json/metallica/post");
String input = "{\"singer\":\"Metallica\",\"title\":\"Fade To Black\"}";
ClientResponse response = webResource.type("application/json")
.post(ClientResponse.class, input);
if (response.getStatus() != 201) {
throw new RuntimeException("Failed : HTTP error code : "
+ response.getStatus());
}
System.out.println("Output from Server .... \n");
String output = response.getEntity(String.class);
System.out.println(output);
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output…
Output from Server ....
Track saved : Track [title=Fade To Black, singer=Metallica]
