Question

How do you set a value to null with org.json.JSONObject in java? I can certainly read if a value is null by using isNull – but it seems like when I put null, it just ignores me:

JSONObject o = new JSONObject();
o.put("key",null);
o.isNull("key"); // returns true, buuuut...
o.has("key");    // returns false
o.isNull("somethingIHaventSetAtAll");    // also returns true, unfortunately

Answer 1

Try to set JSONObject.NULL instead of null:

A sentinel value used to explicitly define a name with no value. Unlike null, names with this value:

• show up in the names() array
• show up in the keys() iterator
• return true for has(String)
• do not throw on get(String)
• are included in the encoded JSON string.

This value violates the general contract of equals(Object) by returning true when compared to null. Its toString() method returns "null".