CODEWITHSUNDEEP
javajsonrestjersey
rtf
rtf

Reputation: 1293

Parse a JSON response as an object

Good evening,
I am a newbie in web services and i just want to write a simple client that simply gets responses from REST calls.
I downloaded and added jersey-bundle-1.17.1.jar to my build path and i found a working piece of code that makes a REST call to a url and returns a response as a String. 

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 manipulations to get the parts of the response that im interested in.

I would prefer a more structured approach, like getting an Object instead of a string
(a JSON Object, a Map<K,V> Object, etc...)

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 Java type java.util.Map<java.lang.String, java.lang.Object>, 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)

Upvotes: 11

Views: 88117

Answers (5)

RazvanParautiu
RazvanParautiu

Reputation: 2938

Simple as that : 

    ObjectMapper mapper = new ObjectMapper();
    String json = "json value";
    MyClass obj = mapper.readValue(json , MyClass .class);

Upvotes: 1

pNut
pNut

Reputation: 221

I recommend you use Jackson for (un)marshalling JSON responses. This can be done is two steps as below.

Step1. create a java bean with member/object names that match the expected response. e.g, MyResponse.class

Step2. use the java bean when reading the entity from the client response.

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);

Upvotes: 12

Yuriy Tumakha
Yuriy Tumakha

Reputation: 1570

If you need to get only few properties from big JSON response, you can use Jersey client and JsonArray or JsonObject entity.

String url = "http://api.goeuro.com/api/v2/position/suggest/en/";
String city = "New York";

Client client = ClientBuilder.newClient();
WebTarget webTarget = client.register(JsonProcessingFeature.class).target(url);
JsonArray jsonArray = webTarget.path(city)
    .request(MediaType.APPLICATION_JSON_TYPE).get(JsonArray.class);

for (JsonObject jsonObject : jsonArray.getValuesAs(JsonObject.class)) {
    JsonObject geoPosition = jsonObject.getJsonObject("geo_position");
    System.out.println(Arrays.asList(
        jsonObject.getString("name"), jsonObject.getString("type"),
        geoPosition.get("latitude"), geoPosition.get("longitude")));
}

Maven dependencies

<dependency>
    <groupId>org.glassfish.jersey.core</groupId>
    <artifactId>jersey-client</artifactId>
    <version>2.22.1</version>
</dependency>
<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-processing</artifactId>
    <version>2.22.1</version>
</dependency>

Upvotes: 6

eugen
eugen

Reputation: 5916

You can use Genson library.

// register genson in jersey client
ClientConfig cfg = new DefaultClientConfig(GensonJsonConverter.class);
Client client = Client.create(cfg);
WebResource webResource = client.resource("http://path/to/service");

// you can map it to a pojo, no need to have a string or map
SomePojo pojo = webResource
                .accept(MediaType.APPLICATION_JSON)
                .get(SomePojo.class);

Upvotes: 7

Nambi
Nambi

Reputation: 12042

see this example ...click this link for more info

// The request also includes the userip parameter which provides the end
// user's IP address. Doing so will help distinguish this legitimate
// server-side traffic from traffic which doesn't come from an end-user.
URL url = new URL(
    "https://www.websitelink.com//folderresponsedata
    + "q=Paris%20Hilton&userip=USERS-IP-ADDRESS");
URLConnection connection = url.openConnection();
connection.addRequestProperty("Referer", /* Enter the URL of your site here */);

String line;
StringBuilder builder = new StringBuilder();
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
while((line = reader.readLine()) != null) {
 builder.append(line);
}

JSONObject json = new JSONObject(builder.toString());
// now have some fun with the results...

Upvotes: 0

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