Android: How to parse JSON Array to string

Question

The JSON file format I need to use looks like this

 [{"fName":"Bob","lName":"Smoe","info":"is tall"},{"fName":"Claire","lName":"Smoegan","info":"has a big forehead"}]

I have an object list of people that I add to a JSON array. The code looks like this

for (int i = 0; i < peopleList.size(); i++){
 try {
 jArray.put(peopleList.get(i));
 }catch (Exception e){
 e.printStackTrace();
 }
}

The problem is, I need to convert it to a string to write to a file, but when I use "jArray.toString()" it returns

"["com.example.zach.projectFile.Person@21b854e0", "com.example.zach.projectFile.Person@21b854e0", "com.example.zach.projectFile.Person@21b85400"....]

How do I get this to return it in the format requested above?

• Andreas: First, that is not parsing. Parsing is the other way (string to json). Second, it depends on what jArray is.
• zachThePerson: jArray is the JSONArray

Answer 1

You are not following the rules for put() on a JSONArray. The parameter is supposed to be:

a JSONObject, JSONArray, String, Boolean, Integer, Long, Double, NULL, or null. May not be NaNs or infinities. Unsupported values are not permitted and will cause the array to be in an inconsistent state.

com.example.zach.projectFile.Person is none of these. What JSONArray is doing is calling toString() on your Person objects and using that as the value for the array.

Your choices are:

1. Implement something like toJSONObject() on Person, which returns a JSONObject representation of the Person (e.g., a JSONObject that, when turned into JSON, results in something like {"fName":"Bob","lName":"Smoe","info":"is tall"}). Then, use put(peopleList.get(i).toJSONObject() to fill in the JSONArray.

2. Use something more sophisticated than the org.json classes, such as Gson.

Also, Andreas' note is correct. You are not parsing JSON. You are generating JSON. Parsing JSON would be converting a String containing JSON into Person objects.

• zachThePerson: I am having a strange problem. I did something similar while waiting for an answer (I used jsonObj.put("fName", fName);) but I am getting a problem where each time I put the object in the array using jArray.put(jsonObj), it fills the array with nothing but the last object enter. So if had 10 people, and the last one is "Clyde" then jArray has 10 entries, but they are all for Clyde. When I step through it adds all the object properties, but then overwrites the array on the jArray.put() method. Any suggestions?
• CommonsWare: @zachThePerson: Create new JSONObject instances per Person. It sounds like you are reusing the same one.
• zachThePerson: THANKS! I moved the "JSONObject jsonObj = new JSONObject();" into the loop and it worked perfectly!