Java get specific data from dynamic JSONObject

MhamadAbuAlGhanam
January 5, 2023
292 views
3 votes
3 Answers

I have a JSON String and convert it to JSONObject.

I want to get specific data from the JSONObject, and every time the JSONObject changes its structure, sometimes it’s in an array inside the JSON and sometimes not.
example:
the first time the JSON arrives like this

{
  "id": "1",
  "Name": "Jack",
  "Value": {
    "data": [
      {"time": "2023", "age": "22"}
    ]
}}

the second time

{ 
  "age": "22",
  "time": "2023",
  "Value": {
    "data": [
      {"Name": "Jack", "id": "1" }
    ]
}}

if I want to get the name in the first JSON

jsonObject.getString("Name")

and for the second one, I would use

jsonObject.getJSONArray("data").getJSONObject(0).getString("Name")

is there a way I can get the value dynamically regardless of where the keys are?

Answers

- HarryCoder
- January 5, 2023 at 4:36 pm
- 0 votes
0
If your API come from an another team or an external provider, the first thing I would suggest to you, is to clearly define a contract. Otherwise, you can use the isNull(String key) method of JSONObject to check if the key exists or not.

An example here:
```
JSONObject jsonObject = new JSONObject(YOUR_JSON_STRING);
String nameValue;

if(jsonObject.isNull("Name")) {
    nameValue = jsonObject.getJSONObject("Value")
                .getJSONArray("data")
                .getJSONObject(0)
                .getString("Name");
} else {
    nameValue = jsonObject.getString("Name");
}

System.out.println(nameValue);
```
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If the JSON strings are always in a similar fashion then you can try a little parser method as provided below. It returns a Key/Value (String/Object) Map:

public static java.util.Map<String, Object> mapJsonObject(String jsonString) {
    String json = jsonString
            .replaceAll("(?i)[\[\]\{\}"]|"?value"?:|"?data"?:|n?", "")
            .replaceAll("\s+", " ");
    String[] keyValueParts = json.split("\s*,\s*");
    java.util.Map<String, Object> map = new java.util.HashMap<>();
    for (String str : keyValueParts) {
        String[] pts = str.split("\s*:\s*");
        map.put(pts[0].trim(), pts[1]);
    }
    return map;
}

To use:

String jsonString = "{n"
            + "  "id": "1",n"
            + "  "Name": "Jack",n"
            + "  "Value": {n"
            + "    "data": [n"
            + "      {"time": "2023", "age": "22"}n"
            + "    ]n"
            + "}}";

java.util.Map<String, Object> map = mapJsonObject(jsonString);
System.out.println(map);

The console window will display:

{id=1, time=2023, age=22 , Name=Jack}

You may consider library Josson.

https://github.com/octomix/josson

Deserialization

Josson josson1 = Josson.fromJsonString(
    "{" +
    "  "id": "1"," +
    "  "Name": "Jack"," +
    "  "Value": {" +
    "    "data": [" +
    "      {"time": "2023", "age": "22"}" +
    "    ]" +
    "  }" +
    "}");

Josson josson2 = Josson.fromJsonString(
    "{ " +
    "  "age": "22"," +
    "  "time": "2023"," +
    "  "Value": {" +
    "    "data": [" +
    "      {"Name": "Jack", "id": "1" }" +
    "    ]" +
    "  }" +
    "}");

Query

*() is a multi-level wildcard search. It returns the first resolvable element.

System.out.println(josson1.getString("coalesce(Name, *().Name)"));
// Output: Jack

System.out.println(josson2.getString("coalesce(Name, *().Name)"));
// Output: ["Jack"]
// It is because "Name" is inside array "data".

System.out.println(josson1.getString("coalesce(Name, *().Name).first()"));
// Output: Jack

System.out.println(josson2.getString("coalesce(Name, *().Name).first()"));
// Output: Jack
// Added function first() to extract the value.

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