字符串无法转换为JSONObject异常

Question

Newbie to Json here, I'm gettin a Value Database of type java.lang.String cannot be converted to JSONObject error when I try and run the following code.I cant make any sense of other answers on here.

       JSONObject jsonObject = new JSONObject(json);
       JSONArray jsonArray = jsonObject.getJSONArray("server_response");
       JSONObject JN = jsonArray.getJSONObject(0);
       String code =JN.getString("code");
       String message = JN.getString("message");
       if (code.equals("reg_true"))
       {
           showDialog("Your Registration has been successful.",message,code);
       }
       else if (code.equals("reg_false"))
       {
           showDialog("Your Registration Failed.",message,code);
       }


   } catch (JSONException e){
       e.printStackTrace();
   }

This is the error

 W/System.err﹕ org.json.JSONException: Value Database of type   java.lang.String cannot be converted to JSONObject
 W/System.err﹕ at org.json.JSON.typeMismatch(JSON.java:111)
 W/System.err﹕ at org.json.JSONObject.<init>(JSONObject.java:160)
 W/System.err﹕ at org.json.JSONObject.<init>(JSONObject.java:173)
 W/System.err﹕ at com.example.project.BackgroundTask.onPostExecute(BackgroundTask.java:133)
 W/System.err﹕ at com.example.project.BackgroundTask.onPostExecute(BackgroundTask.java:29)

Answer 1

The Json you are posting is invalid, trim that {"server_response and closing curly braces too. The remaining Json will be like this, which is valid now,

[{"code":"reg_true","message":"Sucessful registration.Thank you.Enjoy"}]

The you can parse it like here,

JSONArray jsonarray = new JSONArray(json);
JSONObject jsonobject = jsonarray.getJSONObject(0);
String code = jsonobject.getString("code");
String message = jsonobject.getString("message");

UPDATE :

If your Json is as you commented then you can easily retrieve this like

JSONObject jobject = new JSONObject(json);
JSONArray jsonarray = jobject.getJSONArray("server_response");
JSONObject jsonobject = jsonarray.getJSONObject(0);
String code = jsonobject.getString("code");
String message = jsonobject.getString("message");

Answer 2

Your json is invalid. You can check your json on jsonlint.com Correct json should be like this {"server_response":{"code":"reg_true","message":"Sucessful registration.Thank you.Enjoy"}} Since you are using only one json object there is no need to create json array.

Remember if it starts with [ and ends with ] its json array; with curly braces {...} its json object.