Restlet Android client - How to map JSON response from ASP.NET Web API to my Java Objects

Question

I'm kinda having trouble understand how to make the best and map my JASON response from an ASP.NET Web API server into my Java classes.

I use this code to request the server data.

ClientResource res = new ClientResource(ADDRESS_URL + "/exed/students/");
               Representation rep = res.get();
               try {
                   Log.d(TAG, rep.getText());
               } catch (IOException e) {
                   Log.d(TAG, e.getMessage());
               }

I successfuly can retrieve this JSON representation.

{"$id":"1","StudentId":1,"RowVersion":"AAAAAAAAB9M=","User":{"$id":"2","UserId":1,"Username":"1","Password":"1","UserTypeId":1,"FirstName":"George","LastName":"Taskos","RowVersion":"AAAAAAAAB9I=","Student":{"$ref":"1"},"Teacher":null,"UserType":null}}

Now I have these Java classes.

The User.

public class User implements Serializable {

    // Private fields
    //
    private int userId;
    private String username;
    private String password;
    private int userTypeId;
    private String firstName;
    private String lastName;
    private String userType;
    private Timestamp rowVersion;

    // Setters
    // Getters....
 }

And the Student.

public class Student extends User implements Serializable {

    // Private fields
    private List<ClassType> classes;
    private List<ExamTaken> examsTaken;
    private Timestamp rowVersionStudent;
}

How to retrieve the representation into my objects. I've seen so much and I think I'm so dizzy right now to get a solution. I'm not familiar with Java server side or anything so I guess thats why I get frustrated about stuff I read on the tutorials and I think lots of stuff missing from the site, or not clearly explained.

Any simple example at least on get the values out and get them into my object like I do with SQLite cursors. Deserialization from response would be really great too :)

[EDIT]

After Raw suggestion I ended up with this code.

ClientResource res = new ClientResource(ADDRESS_URL + "/exed/students/");
               Representation rep = res.get();

               try {
                   JSONObject response = new JSONObject(rep.getText());
                   Log.d(TAG, rep.getText());
                   JSONObject user = response.getJSONObject("User");
                   Log.d(TAG, "User: " + user.toString());
                   JSONObject student = response.getJSONObject("Student");
                   Log.d(TAG, "Student: " + student.toString());

                   Log.d(TAG, "FirstName: " + user.getString("FirstName"));
               } catch (Exception e) {
                   Log.d(TAG, "Exception: " + e.getMessage());
               }

But getting an Exception with this message: Exception: println needs a message

Stacktrace prints this: Exception: android.util.Log.println_native(Native Method)

and the unhandled exception is this:

03-06 13:07:14.668: ERROR/AndroidRuntime(25353): FATAL EXCEPTION: Thread-13908
        java.lang.NullPointerException: println needs a message
        at android.util.Log.println_native(Native Method)
        at android.util.Log.d(Log.java:155)
        at com.tech.ed.data.access.WebServiceRepository$1.run(WebServiceRepository.java:74)
        at java.lang.Thread.run(Thread.java:856)

I don't exactly understand what it means!

Thank you.

Answer 1

Looks like you just have a series of JSONObjects and strings. Just make one JSONObject for the entire results

JSONObject response = new JSONObject(representation);

then extract out the user and student objects

JSONObject user = response.getJSONObject("User");
JSONObject student = response.getJSONObject("Student");

Then you can get any nested strings, ints or whatever from the corresponding objects with something like

String firstName = user.getString("FirstName");