Jersey Client Example with JSON Support

In this tutorial we will implement a Jersey client example with JSON support. The tools and technologies that I have used are;

• Eclipse 4.3.0
• JBoss AS 7.1.1.Final
• Maven 3.1.1
• JDK 1.7

Project Structure

Our project structure will look like below;

Dependencies

There are two dependencies to use Jersey client and JSON support

<dependency>
	<groupId>com.sun.jersey</groupId>
	<artifactId>jersey-client</artifactId>
	<version>1.18.1</version>
</dependency>

<dependency>
	<groupId>com.sun.jersey</groupId>
	<artifactId>jersey-json</artifactId>
	<version>1.18.1</version>
</dependency>

• jersey-client dependency provides required jars for jersey client.
• jersey-json dependecy includes the jersey-json.jar which provides JSON support.

POJO Entity

We will simply use a Book entity which consists of 4 fields

public class BookEntity {

    private int    id;
    private String title;
    private String author;
    private double price;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    @Override
    public String toString() {

        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("Id : " + this.id + '\n');
        stringBuilder.append("Title : " + this.title + '\n');
        stringBuilder.append("Author : " + this.author + '\n');
        stringBuilder.append("Price : " + this.price + '\n');

        return stringBuilder.toString();
    }
}

Client Configuration

To enable JSON support we have to turn JSONConfiguration.FEATURE_POJO_MAPPING feature on for our jersey client. So we create our client with the following code;

ClientConfig clientConfig = new DefaultClientConfig();
clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, Boolean.TRUE);
Client client = Client.create(clientConfig);

Resource Class

Here are the interface and the implementation class of our resource

@Path("/book-service")
public interface BookResource {

    @GET
    @Path("/list")
    @Produces({ MediaType.APPLICATION_JSON })
    public Map<Integer, BookEntity> getBookList();

    @GET
    @Path("/find")
    @Produces({ MediaType.APPLICATION_JSON })
    public BookEntity findBook(@QueryParam("id") int id);

    @POST
    @Path("/create")
    @Consumes("application/json")
    @Produces("application/json")
    public BookEntity createBook(BookEntity bookEntity);
}

public class DefaultBookResource implements BookResource {
    private Map<Integer, BookEntity> list = new HashMap<Integer, BookEntity>();
    private AtomicInteger idCounter = new AtomicInteger();

    public DefaultBookResource() {

        BookEntity bookEntity1 = new BookEntity();
        bookEntity1.setId(idCounter.getAndIncrement());
        bookEntity1.setAuthor("MargaretWeis");
        bookEntity1.setTitle("TheSoulforge");
        bookEntity1.setPrice(7.99);

        BookEntity bookEntity2 = new BookEntity();
        bookEntity2.setId(idCounter.getAndIncrement());
        bookEntity2.setAuthor("Salvatore");
        bookEntity2.setTitle("Exile");
        bookEntity2.setPrice(9.99);

        list.put(bookEntity1.getId(), bookEntity1);
        list.put(bookEntity2.getId(), bookEntity2);
    }

    @Override
    public Map<Integer, BookEntity> getBookList() {
        return list;
    }

    @Override
    public BookEntity findBook(int id) {
        return list.get(id);
    }

    @Override
    public BookEntity createBook(BookEntity bookEntity) {
        bookEntity.setId(idCounter.getAndIncrement());
        list.put(bookEntity.getId(), bookEntity);

        return bookEntity;
    }
}

• Map<Integer, BookEntity> list is a list that it will have two entities initially.
• AtomicInteger provides to increment and decrement amotically an integer.

GET Request

As I mentioned earlier we have to create our Jersey client with JSON support, then we can start to make requests to available resources. I will first send a GET request to return a BookEntity if it exists.

public class JerseyClient {

    public static void main(String[] args) {

        // Create Jersey client
        ClientConfig clientConfig = new DefaultClientConfig();
        clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, Boolean.TRUE);
        Client client = Client.create(clientConfig);

        // GET request to findBook resource with a query parameter
        String getBookURL = "http://localhost:8080/jersey-client-json-example/services/book-service/find";
        WebResource webResourceGet = client.resource(getBookURL).queryParam("id", "1");
        ClientResponse response = webResourceGet.get(ClientResponse.class);
        BookEntity responseEntity = response.getEntity(BookEntity.class);

        if (response.getStatus() != 200) {
            throw new WebApplicationException();
        }

        System.out.println(responseEntity.toString());
    }
}

Output;

Id : 1
Title : Exile
Author : Salvatore
Price : 9.99

Now lets see how we can get the list from response which contains BookEntities

// GET request to list resource
String getListURL = "http://localhost:8080/jersey-client-json-example/services/book-service/list";
webResourceGet = client.resource(getListURL);
response = webResourceGet.get(ClientResponse.class);
Map<Integer, BookEntity> list = webResourceGet.get(new GenericType<Map<Integer, BookEntity>>() {});

if (response.getStatus() != 200) {
     throw new WebApplicationException();
}

for (Entry<Integer, BookEntity> entry : list.entrySet()) {

     BookEntity bookEntity = entry.getValue();
     System.out.println(bookEntity.toString());
}

• GenericType is the key object to get the list from the response.

Output will be ;

Id : 0
Title : TheSoulforge
Author : MargaretWeis
Price : 7.99

Id : 1
Title : Exile
Author : Salvatore
Price : 9.99

POST Request

Now we will create a BookEntity object to send it associated POST resource.

public class JerseyClient {

    public static void main(String[] args) {

        // Create Jersey client
        ClientConfig clientConfig = new DefaultClientConfig();
        clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, Boolean.TRUE);
        Client client = Client.create(clientConfig);

        // Jersey client POST example
        BookEntity bookEntity = new BookEntity();
        bookEntity.setTitle("LOTR");
        bookEntity.setAuthor("Tolkien");
        bookEntity.setPrice(12.99);
        String postURL = "http://localhost:8080/jersey-client-json-example/services/book-service/create";
        WebResource webResourcePost = client.resource(postURL);
        response = webResourcePost.type("application/json").post(ClientResponse.class, bookEntity);
        responseEntity = response.getEntity(BookEntity.class);

        System.out.println(responseEntity.toString());
    }
}

Finally our output will be;

Id : 2
Title : LOTR
Author : Tolkien
Price : 12.99

You can download the source code from here.