Java: Append key value pair to nested json object

Question

I am given three inputs .

A JSON object (nested)
A node structure
key value pair

My task is to append the key value pair to a node by looking at the node structure and updating the original JSON.

For example, if the inputs are,

JSON Object

Node structure
```
a.b.
```
Key k and value v

The final updated JSON should look like

Please note that the original JSON can be {} also. Then I have to build the whole JSON by looking at the node structure.

Here is my code

making a key value pair

 public JSONObject makeEV(String ele, String val) throws JSONException{      
   JSONObject json =new JSONObject();
   json.put(ele, val);
   return json;
 }

Appending it to JSON

public void modifiedJSON(JSONObject orgJson, String nodeStruct, JSONObject ev) throws JSONException{
JSONObject newJson = new JSONObject();
JSONObject copyJson = newJson;

char last = nodeStruct.charAt(nodeStruct.length()-1);
String lastNode = String.valueOf(last);

int i = 0; 
while(orgJson.length() != 0 || i< nodeStruct.length()){

    if(orgJson.length() ==0){
        if(nodeStruct.charAt(i) == last){
            newJson.put(String.valueOf(last), ev.toString());
        }else{
            newJson.put(String.valueOf(nodeStruct.charAt(i)), "");
        }
        newJson = newJson.getJSONObject(String.valueOf(nodeStruct.charAt(i)));

    }
    else if(i >= nodeStruct.length()){
        if(orgJson.has(lastNode)){
            newJson.put(String.valueOf(last), ev.toString());
        }else{

        }
    }
}
}

I am stuck here. Please help. Thanks in advance.

Your node structure should be rather a.b.key, doesn't it?

Nicolas Filotto
– Nicolas Filotto

2016-10-06 12:07:38 +00:00
Commented Oct 6, 2016 at 12:07 — Nicolas Filotto
– Nicolas Filotto, Commented Oct 6, 2016 at 12:07
yeah. that's fine too

Athul Sukumaran
– Athul Sukumaran

2016-10-06 12:21:50 +00:00
Commented Oct 6, 2016 at 12:21 — Athul Sukumaran
– Athul Sukumaran, Commented Oct 6, 2016 at 12:21

Nicolas Filotto · Accepted Answer · 2016-10-06 12:56:48Z

4

It could be done using String#split(regex) as next:

public void modifiedJSON(JSONObject orgJson, String nodeStruct, 
                         String targetKey, String value)  {
    // Split the keys using . as separator 
    String[] keys = nodeStruct.split("\\.");
    // Used to navigate in the tree
    // Initialized to the root object
    JSONObject target = orgJson;
    // Iterate over the list of keys from the first to the key before the last one
    for (int i = 0; i < keys.length - 1; i++) {
        String key = keys[i];
        if (!target.has(key)) {
            // The key doesn't exist yet so we create and add it automatically  
            target.put(key, new JSONObject());
        }
        // Get the JSONObject corresponding to the current key and use it
        // as new target object
        target = target.getJSONObject(key);
    }
    // Set the last key
    target.put(targetKey, value);
}

edited Oct 6, 2016 at 12:56

answered Oct 6, 2016 at 12:28

Nicolas Filotto

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4 Comments

Athul Sukumaran Over a year ago

Actually, here ev is the key value pair that i need to insert.

Athul Sukumaran Over a year ago

Can you make the required changes?

Athul Sukumaran Over a year ago

Thanks. What if key was given as a separate argument and node structure was a.b.?

Nikita Over a year ago

Magnificent code snippet, like how it short and expressive and with comments. Saved me some hours of inventing the algorithm and searching for documentation =)))

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