Retrieve name of fields of a JSONObject - Java

Question

I have to retrieve all name of fields of JSONObject in Java. For example, this is a JSON:

{
"name" : {
        "first" : "John",
        "last" : "McCarthy"
    },
"birth" : ISODate("1927-09-04T04:00:00.000Z"),
"death" : ISODate("2011-12-24T05:00:00.000Z"),
"contribs" : [ 
        "Lisp", 
        "Artificial Intelligence", 
        "ALGOL"
    ]
}

This JSON object is just an example, I can't know what a JSONObject contains since I import it. I don't have any information about the name of fields to use Gson/Jackson to deserialization.

Suppose I have a JSONObject myDocJson that contains the previous JSON Object, I use an iterator:

Iterator<?> keys = myDocJson.keySet().iterator();
while(keys.hasNext()) {
System.out.println(keys.next());
}

And as a result I get:

name
birth
death
contribs

But for example I don't have name.first and name.last . So this iterator does not work with innested Object.

Answer 1

You are only printing the keys.

To get the values, try

JSONObject object = null; // your json object
for (Object key : object.keySet()) {
    System.out.println(key + "=" + object.get(key)); // to get the value
}

EDIT

And for the objects inside of your JSONObject try

JSONObject object = null; // your json object
for (Object key : object.keySet()) {
    System.out.println(key + "=" + object.get(key)); // to get the value
    for (Object subKey : ((JSONObject) object.get(key)).keySet()) {
        System.out.println(subKey + "=" + object.get(subKey));
    }
}

Answer 2

I belive that you need know the json structure. If be necessary, iterate over the childrens.

Edit: I was wrong. This question can help you, see Sean Patrick Floyd's answer: JSON - Iterate through JSONArray