无法解析Java JSON字符串

Question

From my server is get a JSON response like this:

String json = getJsonFromServer();

The server returns this reply (with the double quotes in the beginning and end):

"{\"error\":\"Not all required fields have been filled out\"}";

I then want to get the error field. I have tried to use the JSONObject class to get the string, but it does not work.

System.out.println("The error is: " + new JSONObject().getJSONObject(response).getString("error");

Answer 1

You seem to be using the wrong JSONObject constructor; in your example, you are trying to fetch an object from a newlay created object - it will never exist.

Try this:

String response = "{\"error\":\"Not all required fields have been filled out\"}";

JSONObject json = new JSONObject( response );

String error = json.getString( "error" );

System.out.println( error );

Yields

Not all required fields have been filled out

edit

Now that you have completely changed the question...

Why not just first strip the first and last char?

So if

String response = "\"{\"error\":\"Not all required fields have been filled out\"}\"";

response = response.substring(1, response.length() - 1));

// Now convert to JSONObject

Answer 2

Your response object has exactly this string?

{"error":"Not all required fields have been filled out"}

The code below printed the expected output:

    Object responseObject = "{\"error\":\"Not all required fields have been filled out\"}";
    JSONObject jsonObject = new JSONObject(responseObject.toString());
    String errorContent = jsonObject.getString("error");
    System.out.println(errorContent);

Answer 3

I have try

String response = "{\"error\":\"Not all required fields have been filled out\"}";
    JSONParser parser = new JSONParser();
    try {
        JSONObject json = (JSONObject) parser.parse(response);

        System.out.println(json.get("error").toString());
    } catch (ParseException ex) {

    }

It have working, you can try it and don't forget add json lib json-simple