Get keys from multiple JSON objects

Question

I have a JSON object that contains undetermined pattern and I need to get all keys of the json object and the sub-objects.

Here's an example of a JSON file:

{
  "users": {
    "address": [
      {
        "rue": "ruetest",
        "postal": 1111
      },
      {
        "rue": "ruetest",
        "postal": 2222
      }
    ],
    "type": "string",
    "user": [
      {
        "argent": 122,
        "id": 1,
        "nom": "user1",
        "prenom": "last1"
      },
      {
        "argent": 200,
        "id": 2,
        "nom": "user2",
        "prenom": "last2"
      },
      {
        "argent": 1205,
        "id": 3,
        "nom": "user3",
        "prenom": "last3"
      }
    ]
  }
}

and I need to have output like this:

[users,type,address,user,argent,id,nom,prenom] or something like this

Cesar van der Poel · Accepted Answer · 2021-02-16 21:29:12Z

1

I don't think there's really a built-in way to do this, but you could achieve your goal by making a function that does it. Something like (in pseudocode):

public Set getJsonKeys(JSON json) {
  Set s = new Set();
  for (Entry e : json.entrySet()) {
    s.add(e.key);
    if (e.value instanceof JSON) s.addAll(getJsonKeys(e.value));
  }
  return s;
}

I chose a Set rather than List to prevent duplicate entries. If you want to include keys of lists just add a check if e.value is a list and if so, iterate over elements and add getJsonKeys(element) for all elements.

answered Feb 16, 2021 at 21:29

Cesar van der Poel

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1 Comment

Hanini Mohamed Over a year ago

thank you for responding ,i already did somthing similaire but i hoped to find buily in function . I still need to get further and have somthing like this [users,users.type,users.address,users.user,users.user.argent,users.user.id,users.user.nom,users.user.prenom] or somthing similaire in order to be able to acces any value i want to acces

queeg · Accepted Answer · 2021-02-16 23:47:14Z

0

Have you tried the Genson Java Collections mode? It would give you easy generic access to arbitrary JSON files in java.

answered Feb 16, 2021 at 23:47

queeg

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1 Comment

Hanini Mohamed Over a year ago

i can not use it because my json object does not have a generic type so i can not predefine a java class to serialise it

peter · Accepted Answer · 2021-02-17 08:05:09Z

0

If you use the fastjson framework, I think you can use the following code to get all the keys:

JSONObject jsonObject = new JSONObject(jsonData);
Iterator keys = jsonObject.keys();
while (keys.hasNext()){
        String key = String.valueOf(keys.next());
    }

answered Feb 17, 2021 at 8:05

peter

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2 Comments

k314159 Over a year ago

Does keys() recurse into all sub-objects or does it give you only the top-level keys?

peter Over a year ago

It will give you all the keys

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