JAVA Google App Engine + Facebook API + GSON = Trouble with Javabean - google-app-engine

Question

I am trying to get the user's friends list from Facebook.
The problem seems to be the Javabean...
FBUser fbuser = new Gson().fromJson(jsonStr, FBUser.class);
public class FBUser implements Serializable {
private static final long serialVersionUID = -3154429420153433117L;
private String id;
private String name;
private String email;
private Friends friendsList = new Friends();
private FBUser() { }
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public List<Data> getFriendsList() {
return friendsList.getData();
}
public static class Friends implements Serializable {
private static final long serialVersionUID = 6991758772193514527L;
private List<Data> data;
private Friends() { }
public List<Data> getData() {
return data;
}
public void setData(List<Data> data) {
this.data = data;
}
public class Paging implements Serializable {
private static final long serialVersionUID = 1689816298710621080L;
private String next;
private Paging() { }
public String getNext() {
return next;
}
public void setNext(String next) {
this.next = next;
}
}
}
public class Data implements Serializable {
private static final long serialVersionUID = -5008541658519841090L;
private String id;
private String name;
private Data() { }
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
}
Json:
json: {"id":"10861234","name":"Whatever","email":"whatever\u0040gmail.com","friends":{"data":[{"name":"Someone","id":"10861234"},{"name" ...43"}],"paging":{"next":"https:\/\/graph.facebook.com\/10861234\/friends..."}}}
The fields ID, Name and Email I can retrieve succesfully... but the friendsList is null... =(
Maybe it is the way I am trying to get it from the nested class, any suggestions on that?

Answer 1

There is no friendsList in your JSON (or, there's no friends in your Java class - whichever way you'd like to look at it). Gson silently ignores anything in the JSON that is not present in your classes.
You have a field friends whose value is an object. That object has a field data which is an array of objects and a field paging which is another object.
You need to write Java classes that match that structure. You're ... close.
In your FBUser class change:
private Friends friendsList = new Friends();
to:
private Friends friends = new Friends();
or:
#SerializedName("friends")
private Friends friendsList = new Friends();
Then in your Friends class you need to add:
private Paging paging = new Paging();
Also note that you don't have to initialize these values unless you specifically don't want them to be non-null when using these classes elsewhere.