Android Json and null values

Question

How can I detect when a json value is null? for example: [{"username":null},{"username":"null"}]

The first case represents an unexisting username and the second a user named "null". But if you try to retrieve them both values result in the string "null"

JSONObject json = new JSONObject("{\"hello\":null}"); json.put("bye", JSONObject.NULL); Log.e("LOG", json.toString()); Log.e("LOG", "hello="+json.getString("hello") + " is null? "                 + (json.getString("hello") == null)); Log.e("LOG", "bye="+json.getString("bye") + " is null? "                 + (json.getString("bye") == null)); 

The log output is

{"hello":"null","bye":null} hello=null is null? false bye=null is null? false 

Answer 1

Try with json.isNull( "field-name" ).

Reference: http://developer.android.com/reference/org/json/JSONObject.html#isNull%28java.lang.String%29

Answer 2

Because JSONObject#getString returns a value if the given key exists, it is not null by definition. This is the reason JSONObject.NULL exists: to represent a null JSON value.

json.getString("hello").equals(JSONObject.NULL); // should be false json.getString("bye").equals(JSONObject.NULL); // should be true