Java – parses JSON responses into objects

Good evening,

import javax.ws.rs.core.MediaType;

import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;

public class TestJerseyClient {
    public static void main(String[] args) {
        try {
            Client client = Client.create();
            WebResource webResource = client
                    .resource("http://path/to/service");

            ClientResponse response = webResource
                    .accept(MediaType.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();
        }
    }
}

But I don't want to do string manipulation to get the response part I'm interested in

I prefer more structured methods, such as getting objects rather than strings (JSON objects, map < K, V > objects...)

Try #1 – map < K, V >

Sep 15,2013 2:46:13 AM com.sun.jersey.api.client.ClientResponse getEntity
SEVERE: A message body reader for Java class java.util.Map,and Java type java.util.Map<java.lang.String,java.lang.Object>,and MIME media type application/json; charset=UTF-8 was not found
Sep 15,2013 2:46:13 AM com.sun.jersey.api.client.ClientResponse getEntity
SEVERE: The registered message body readers compatible with the MIME media type are:
application/json; charset=UTF-8 ->
  com.sun.jersey.json.impl.provider.entity.JSONJAXBElementProvider$App
  com.sun.jersey.json.impl.provider.entity.JSONRootElementProvider$App
  com.sun.jersey.json.impl.provider.entity.JSONListElementProvider$App
*/* ->
  com.sun.jersey.core.impl.provider.entity.FormProvider
  com.sun.jersey.core.impl.provider.entity.StringProvider
  com.sun.jersey.core.impl.provider.entity.ByteArrayProvider
  com.sun.jersey.core.impl.provider.entity.FileProvider
  com.sun.jersey.core.impl.provider.entity.InputStreamProvider
  com.sun.jersey.core.impl.provider.entity.DataSourceProvider
  com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General
  com.sun.jersey.core.impl.provider.entity.ReaderProvider
  com.sun.jersey.core.impl.provider.entity.DocumentProvider
  com.sun.jersey.core.impl.provider.entity.sourceProvider$StreamSourceReader
  com.sun.jersey.core.impl.provider.entity.sourceProvider$SAXSourceReader
  com.sun.jersey.core.impl.provider.entity.sourceProvider$DOMSourceReader
  com.sun.jersey.json.impl.provider.entity.JSONJAXBElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLRootObjectProvider$General
  com.sun.jersey.core.impl.provider.entity.EntityHolderReader
  com.sun.jersey.json.impl.provider.entity.JSONRootElementProvider$General
  com.sun.jersey.json.impl.provider.entity.JSONListElementProvider$General

com.sun.jersey.api.client.ClientHandlerException: A message body reader for Java class java.util.Map,and MIME media type application/json; charset=UTF-8 was not found
    at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:561)
    at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:535)
    at com.sun.jersey.api.client.WebResource.handle(WebResource.java:696)
    at com.sun.jersey.api.client.WebResource.access$300(WebResource.java:74)
    at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:512)
    at rest.TestJerseyClientAdvanced.main(TestJerseyClientAdvanced.java:36)

Solution

I suggest you use Jackson to group JSON responses This can be done in the following two steps

Step 1 Create a java bean whose member / object name matches the expected response For example, myresponse class

Step 2 Java beans are used when reading entities from client responses

private static ClientConfig clientConfig = new DefaultClientConfig();
clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING,Boolean.TRUE);

ClientResponse response =  Client.create(clientConfig).
            resource(uri).accept(MediaType.APPLICATION_JSON).
            header("content-type",MediaType.APPLICATION_JSON).
            get(MY_RESPONSE.class); 
MyResponse output = response.getEntity(MyResponse.class);