JSONObject is an unordered collection of name/value pairs.It does not maintain the insertion order of the keys. Now Question is how to maintain the insertion order of keys an a JSONObject.
There is no direct way make the JSONObject orderable. But there are
multiple hooks that can be used to acheive target goal (maintaing order
in JSONObject).
If you want to maintain the original order in the JSONObject same as the
input JSON String, you can adopt any one of the hooks mentioned in this
page.
If you are using org.json.simple.JSONObject of Simple-JSON libarty,
there is no hook to maintain the insertion order in the keys of JSON
Object as org.json.simple.JSONObject class extends HashMap class (which
does not maintain any order). So if you are using
org.json.simple.JSONObject, change to org.json.JSONObject object of gson
library. Both org.json.simple.JSONObject and org.json.simple.JSONObject
work in similar fashion so moving from org.json.simple.JSONObject to
org.json.simple.JSONObject is easily doable.
if you are using org.json.JSONObject, there are multiple hooks which can
be used to maintain order in the keys on JSONObject.
Example 1:
org.json.simple.JSONObject uses HashMap object as instance varible
(varibale name is 'map'), Through reflection we can assign a
LinkedHashmap object on the map variable, we can acheive our targeted
goal.
Sample Java Code:
private JSONObject sortAJsonObject(org.json.JSONObject jsonObject) throws Exception {
Iterator keySetIterator = jsonObject.keys();
Map map = new TreeMap();
while (keySetIterator.hasNext()) {
Object key = keySetIterator.next();
Object value = jsonObject.get("" + key);
map.put(key.toString(), value);
}
Set keySet = map.keySet();
for (Object key : keySet) {
jsonObject.remove("" + key);
}
Field filedMap = jsonObject.getClass().getDeclaredField("map");
filedMap.setAccessible(true);// as map is a private variable
filedMap.set(jsonObject, new LinkedHashMap<>());
filedMap.setAccessible(false);
// Add all keys
for (Object key : keySet) {
Object value = map.get(key);
jsonObject.put("" + key, value);
}
return jsonObject;
}
Example 2:
You can use com.google.gson.Gson and com.google.gson.JsonObject class to
convert a json string to JsonObject. it maintains the order of the key
present in input JSON String.
Sample Java Code:
private static void tm() {
String str = "";
str = str + " {\n";
str = str + " \"bpay\": 0,\n";
str = str + " \"wallet\": 0,\n";
str = str + " \"cash\": 0,\n";
str = str + " \"client_name\": \"DDR 1\"\n";
str = str + " }\n";
com.google.gson.Gson gson = new Gson();
com.google.gson.JsonObject jsonObject = gson.fromJson(str, JsonObject.class);
System.out.println("jsonObject=" + jsonObject);
}
Example 3:
Get the JSONObject.java file. Change the map variable. Assign a
LinkedHashMap object to the map variable and to class Change from
HashMap() to LinkedHashMap()
This is not a very good option. This option is not recomended.
public JSONObject() {
this.map = new LinkedHashMap();
}
