create JSONArray from JSONObject

Question

Good day all

I am having trouble parsing a JSONArray from a JSONObject. I might just be misunderstanding.

Creating the JSONObject to send:

int i = 0;
JSONArray jsonArray = new JSONArray();
String line;

while ((line = bufferedReader.readLine()) != null) {
    JSONObject rule = new JSONObject().put("rule", line);
    jsonArray.put(i,rule);
    i++;
}
return (new JSONObject().put(jsonStrings.REQUEST_RULES_ALL_RESPONSE, jsonArray));

This send a json array within a json object, to make things simpler. This is correct.

the returned object is in this format:

{"REQUEST_RULES_ALL_RESPONSE":[ 
        {"rule":"something"},
        {"rule":"something"},
        {"rule":"something"}  ]}

I would like to parse this into a List RULES. Reading the JSONObject recieved:

//this returns the object as described above
JSONObject jsonObject = serverData.SendData(new JSONObject().put(jsonStrings.REQUEST_RULES_ALL, " ")); 

//Trying to Convert to JSONArray, the get strings are correct, 
//notice the REQUEST and REQUEST RESPONSE.

//problem line below
JSONArray JSONFirewallRules = new JSONArray ((JSONArray)jsonObject.get(jsonStrings.REQUEST_RULES_ALL_RESPONSE));  

ERROR: org.json.JSONException: Not a primitive array: class org.json.JSONArray

I do not understand why this is a problem. I would like to get the JSONArray from the object.

Answer 1

In the problematic line, instead of casting to a JSONArray, use getJSONArray:

JSONArray JSONFirewallRules = jsonObject.getJSONArray(jsonStrings.REQUEST_RULES_ALL_RESPONSE); 

However the exception isn't a cast exception, but a constructor exception where you are trying to build a JSONArray object from an unsupported list of items, which is another JSONArray :)

Answer 2

jsonObject.getJSONArray(key) throw exception in case key not found
Use jsonObject.opt... methods. These methods just return null if key not found in json object
Use jsonObject.optJSONArray(key) instead of jsonObject.getJSONArray(key)