i'm trying to transfer a list of objects from a server to a client using a web service. The data should be transfered in json format. I'm using jersey for the JAX-RS implementation and gson to deserialise the json string on the client side. I kept getting a parse error, even though i was using the recommended practice for list deserilization with gson (see below). I have found out that the json string which i am getting in the response is different than the one which i should receive in order for the gson deserilizer to work.

This is the reponse i'm getting from the web service:

{"activity":[{"activityName":"c","id":"3"},{"activityName":"c","id":"3"},{"activityName":"c","id":"3"}]}

But this is the correct response i should receive in order for the gson to deserialize the string to a List: [{"id":3,"activityName":"c"},{"id":3,"activityName":"c"},{"id":3,"activityName":"c"}]

You can see the added header/wrapper "activity" in the begining of the first string.

Here is the web service code:

@Path("ws")
public class IiwsServices {

@POST
@Path("/listActivities")
@Produces(MediaType.APPLICATION_JSON)
public List<Activity> listActivities() {

    List<Activity> list = new ArrayList<Activity>();

    Activity act = new Activity();
    act.setId(1);
    act.setActivityName("a");
    list.add(act);

    act.setId(2);
    act.setActivityName("b");
    list.add(act);

    act.setId(3);
    act.setActivityName("c");
    list.add(act);
    return list;
}

This is the client code:

public class Main {
public static void main(String[] args) {
    try {

        Client client = Client.create();

        WebResource webResource = client
           .resource("http://localhost:8080/iiws.ws.test/ws/listActivities");

        ClientResponse response = webResource.accept(MediaType.APPLICATION_JSON)
                   .post(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);

        List<Activity> list = new ArrayList<Activity>();

        Activity act = new Activity();
        act.setId(1);
        act.setActivityName("a");
        list.add(act);

        act.setId(2);
        act.setActivityName("b");
        list.add(act);

        act.setId(3);
        act.setActivityName("c");
        list.add(act);

        Gson gson = new GsonBuilder().create();
        String jsonString = gson.toJson(list);

        System.out.println(jsonString);

        List<Activity> list = gson.fromJson(output, new   TypeToken<List<Activity>>(){}.getType()); // <-- Deserialize exception here

        for (int i = 0; i < list.size(); i++) {
            Activity x = list.get(i);
            System.out.println(x);
        }

      } catch (Exception e) {

        e.printStackTrace();

      }

}

****OK I believe I have found the answer****

OK finally found solution Here i found a similar question after googling for jersey and jackson : Jersey client can not deserializable json services

And this helps as well: JSON POJO support

Button line is that if not explicitely defined in the web.xml, jersey+jaxb is used instead of jersey+jackson