How to customize the response body JSON conversion in Retrofit?

Question

I'm using Retrofit to implement a Rest Client and I ran into some trouble when trying to convert the response body to my model Object.

I have the following in my interface:

@POST("/users")
void createUser(@Body RegisterUserToken token, Callback<User> callback);

My User class is basically a POJO with:

public class User {

    private int id;
    private String username;
    private String email;
    private String language;
    // getters and setters...
}

And this is how I use the Rest Client:

restClient.createUser(token, new Callback<User>() {
    @Override
    public void success(User user, Response response) {
        // ...problem is here, with the user object
    }

    @Override
    public void failure(RetrofitError error) {
        // ...
    }
});

The problem I'm having is that the response body is not being converted to a User object. I'm pretty sure the problem is that the server is returning:

{"user":{"id":13,"username":"john","email":"[email protected]","language":"eng"}}

Instead of just:

{"id":13,"username":"john","email":"[email protected]","language":"eng"}

Given that I can't really modify the server code, how can I customize Retrofit/GSON to correctly convert this response body to my User object?

Answer 1

Change the POJO class like this:

public static class User {
    UserData user;
}   

public static class UserData {
    private int id;
    private String username;
    private String email;
    private String language;
}