Append 到 JSONObject，使用 org.json 将 object 写入文件 ZD52387880E1EA22817A72D3752?

Question

To start, I have researched this extensively, but because org.json and json.simple use the same names for datatypes it is very confusing and does not apply to my specific instance. I need to take an existing JSONObject, append that object with another JSONObject, and write that new object to a file. I can cast the other JSONObject to a String if that makes it easier to process.

Example:

JSONObject jObj = new JSONObject();
... make new JSONObject jo ...
jObj.put(jo);
... then somehow save the appended jObj to a file ...

Answer 1

If I understand correctly you're using org.json

In that case just use:

PrintWriter myFile = new PrintWriter(myFilePath, "UTF-8");
String source = "{\"test\": \"my json object\"}";
JSONObject jObj = new JSONObject();
JSONObject jObjNew = new JSONObject(source);
jObj.put("jObjNew",jObjNew);
myFile.println(jObj.toString(4));

This is the output in the File at "myFilePath":

{
    "jObjNew": {
        "test": "my json object"
    }
}

Answer 2

The result from literally appending one JSONObject to another JSONObject would not be valid JSON. This is why the org.json library prevents you from doing precisely that. For example, take this valid JSON String:

{ "Foo": "Bar" }

And append that to another valid another valid JSON String:

{ "Stack": "Overflow" }

Would result in invalid JSON:

{ "Stack": "Overflow" }{ "Foo": "Bar" }

You can check JSON text for validity at https://jsonlint.com/

To combine those, you have at least two options:

1. Put both into one JSONObject, each with a uniquely named String key.
2. Put both into one JSONArray.

Here is the code for both of those solutions:

    JSONObject existingJSON = new JSONObject( "{ \"Foo\": \"Bar\" }" );
    JSONObject newJSON = new JSONObject( "{ \"Stack\": \"Overflow\" }" );
    
    // JSONObject solution:
    JSONObject combinedObject = new JSONObject();
    combinedObject.put( "newJSON", newJSON );
    combinedObject.put( "existingJSON", existingJSON );
    System.out.println( combinedObject );
    System.out.println( combinedObject.get( "newJSON" ) );
    System.out.println( combinedObject.get( "existingJSON" ) );

    // JSONArray solution:
    JSONArray combinedArray = new JSONArray();
    combinedArray.put( newJSON );
    combinedArray.put( existingJSON );
    System.out.println( combinedArray );
    System.out.println( combinedArray.get( 0 ) );
    System.out.println( combinedArray.get( 1 ) );

The output should look like this:

{"existingJSON":{"Foo":"Bar"},"newJSON":{"Stack":"Overflow"}}
{"Stack":"Overflow"}
{"Foo":"Bar"}
[{"Stack":"Overflow"},{"Foo":"Bar"}]
{"Stack":"Overflow"}
{"Foo":"Bar"}

As shown in the code above, you can access your two original JSONObjects using combinedObject.get( "keyname" ) or combinedArray.get( <array index #> ) .