用于将JSONObject转换为JSONArray的ClassCastException

Question

i'm using the simple JSON library to write a match log analyzer for tf2. The code successfully gets all log IDs but cannot get to the actual log itself. The error is that

Exception in thread "main" java.lang.ClassCastException: org.json.simple.JSONObject cannot be cast to org.json.simple.JSONArray

However, in the code, I've already casted an object to an array. Here is a snippet of the code, where parseJSON returns a JSONObject and logIDList contains a list of all the log ids:

JSONArray playerData = (JSONArray)parseJSON("http://logs.tf/json_search?player=" + steamID64).get("logs");
    //....
        JSONArray tempJSONArray = (JSONArray)parseJSON("http://logs.tf/json/" + logIDList.get(j)).get("players");

The second attempt at casting the JSONObject always throws a casting error. Using IntelliJ's debugger, parseJSON successfully parses the JSON and returns multiple keys.

The first JSON file is structured as so:

{
 "logs": [
{
  "date": 1512093930, 
  "id": 1893064, 
  "title": "UGC 6v6 Match: RED vs -rep"
},
],
} 

The second JSON file is structured as so:

{  
"players" : {
"[U:1:61383870]":{(Player Stats)}
},
}

My assumption is that it is due to there being a key within a key or something like that? Not sure why this tells me I can't cast this to an array, when I did it with another JSONObject.

Answer 1

You are downcasting from Object to Array. This works if the instance really is an array, and fails if it not (like a map). You should always protect downcasts with instanceof checks in general, like:

JSONArray playerData;
JSONObject playerJson = parseJSON("http://logs.tf/json_search?player=" + steamID64).get("logs");
if (playerJson instanceof JSONArray) {
    playerData = (JSONArray) playerJson;
} else {
    throw new IllegalStateException("wrong Json type " + playerJson)
}

As you can see from the json you posted:

"logs": [ ...]

log is an array, while

"players" : { ... }

players is a map.

Answer 2

As it is clearly visible that the JSONObject which you have metioned is kind of map, so you can't simply cast it to JSONArray.For this you can create your JSONArray and then proceed. To create JSONObject to JSONArray you can use:

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