android/java - Parsing JSON responses of different structure

Question

I have REST web service that has different responses containing some user information like this

{"id": 1,"fullname": "NV","login": "bravenewuser","sex": "M","mail":"aaa@gmail.com","photo": "","status": "","birthDate": "1900-01-11T00:00:00Z","registrationDate": "1900-05-13T00:00:00Z","phoneNumber": "9010"}

and like this

[{"id":2,"userId":0,"timeStart":"2017-08-21T13:05:00Z","active":true,"title":"Woman","artist":"Wolfmother","length":"00:04:00"},{"id":1,"userId":0,"timeStart":"2017-08-20T13:05:34Z","active":true,"title":"Dont call","artist":"Royal blood","length":"00:03:20"}]

with list of user's listenings

Say I have two classes User and Listening (may be in addition I need ListOfListenings wrapper-class). May be in future i would like to retrieve some more information from service and get responses having some another structure.

The question is what is the best way to parse different responses in one place (method or class) of the code?

I use com.loopj.android.http.AsyncHttpClient for calling service. So can I try something like this:

1. Write one common response handler for different types of response:

    public class CommonResponseHandler <T extends Entity> extends AsyncHttpResponseHandler { private T response; public T getResponse() { return this.response; //return pasing result } @Override public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) { /*parsing response body into this.response*/ } @Override public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) { ///... } } 

2. and then call service like this

    public User getUser(String url, RequestParams someparams) { AsyncHttpClient client = new AsyncHttpClient(); CommonResponseHandler<User> handler = new CommonResponseHandler<>(); client.get(url, someparams, handler ); return handler.getResponse(); } 

Can I simplify parsing different types of responses by this way. And if not, what is better (or even the best) way to solve this problem? Thank you.

Answer 1

You need two response handlers.

public class ObjectResponseHandler <T extends Entity> extends AsyncHttpResponseHandler {
    private T response;

    public T getResponse() {
        return this.response; //return pasing result
    }
}

And,

public class ArrayResponseHandler <T extends Entity> extends AsyncHttpResponseHandler {
    private List<T> responses;

    public List<T> getResponses() {
        return this.responses; //return pasing result
    }
}

And, if your JSON is only going to be a JsonArray or JsonObject. You can check for it using

 anyJsonString.startsWith("[") => true => use ArrayResponseHandler
 anyJsonString.startsWith("{") => true => use ObjectResponseHandler

If you want to keep using getResponse() as an object, you should create something like

public class ListWrapper<T> {

    List<T> list;

    public ListWrapper (List<T> list) { this.list = list; }

    public List<T> getList () { return list; }        

}

And, use it in ArrayResponseHandler, like

 public ListWrapper getResponse() {
     return new ListWrapper<T>(responses);
 }