Gson throws "BEGIN_OBJECT expected but BEGIN_ARRAY found" - how to use TypeToken

Question

Trying out Gson for the first time instead of looping through the JSON objects for speed.

This is my input data set for parsing

{
  "data": [
    {
      "access_token": "XXXXX", 
      "category": "Community", 
      "name": "Startup notes by Vrashabh", 
      "id": "XXXXX", 
      "perms": [
        "ADMINISTER", 
        "EDIT_PROFILE", 
        "CREATE_CONTENT", 
        "MODERATE_CONTENT", 
        "CREATE_ADS", 
        "BASIC_ADMIN"
      ]
    }, 
    {
      "access_token": "XXXX", 
      "category": "Community", 
      "name": "Clean Bangalore", 
      "id": "XXXXX", 
      "perms": [
        "ADMINISTER", 
        "EDIT_PROFILE", 
        "CREATE_CONTENT", 
        "MODERATE_CONTENT", 
        "CREATE_ADS", 
        "BASIC_ADMIN"
      ]
    }, 
    {
      "access_token": "XXXXX", 
      "category": "Internet/software", 
      "name": "Getmeetin", 
      "id": "XXXXX", 
      "perms": [
        "ADMINISTER", 
        "EDIT_PROFILE", 
        "CREATE_CONTENT", 
        "MODERATE_CONTENT", 
        "CREATE_ADS", 
        "BASIC_ADMIN"
      ]
    }
  ], 
  "paging": {
    "cursors": {
      "before": "MTU3MzE3MTA0MjkyMjY4MQ==", 
      "after": "MjcyMTIwMzE2Mjk3NzI5"
    }
  }
}

And this is my gson mapping class

public class AccountsResponse {
    ArrayList<AcResponseData> data;
    ArrayList<PagingData> paging;

    public class AcResponseData {
        public String access_token;
        public String category;
        public String name;
        public String id;
        public String[] perms;
    }
    public class PagingData{
        public Cursors cursors;
    }
    public class Cursors{
        public String before;
        public String after;
    }
}

Code for parsing the data

AccountsResponse responseAccounts = gsonResponse.fromJson(response.getRawResponse(), AccountsResponse.class);

I Know I am supposed to not expect magic in terms of data conversion, I found the other questions on SO that ask me to implement TypeToken but I couldn't get it working for this case. How do I use TypeToken to get this data into the ORM I wouldn't mind not reading that paging data also actually, if that needs to be eliminated from the ORM

UPDATE Changed the ORM as below but now I get

java.lang.StackOverflowError

Where's the code you're using to parse the JSON data? – iRuth Feb 14 '15 at 02:16 — iRuth, Feb 14 '15 at 02:16

score 2 · Accepted Answer · answered Feb 14 '15 at 04:14

2

The problem is in your AccountsResponse class. It should be an object PagingData not an ArrayList, because from the json response in your question, "paging" is a JSON object not a JSON array. So, you should declare paging as a PagingData object not as an ArrayList of PagingData objects. That should fix it.

public class AccountsResponse {
    ArrayList<AcResponseData> data;
    PagingData paging;

    public class AcResponseData {
        public String access_token;
        public String category;
        public String name;
        public String id;
        public String[] perms;
    }
    public class PagingData{
        public Cursors cursors;
    }
    public class Cursors{
        public String before;
        public String after;
    }
}

Let me know if this helps.

answered Feb 14 '15 at 04:14

iRuth

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Yes I figured that out :) Thanks! – Vrashabh Irde Feb 14 '15 at 04:30
well unfortunately/ironically now I'm getting java.lang.StackOverflowError – Vrashabh Irde Feb 14 '15 at 04:56
I suppose that happens if there is a circular reference, but I dont see any in the data – Vrashabh Irde Feb 14 '15 at 05:16
Marking this correct, solved my original problem anyway, will open a new question for a follow up problem – Vrashabh Irde Feb 28 '15 at 06:04

Gson throws "BEGIN_OBJECT expected but BEGIN_ARRAY found" - how to use TypeToken

1 Answers1