The JSON string is converted into a JSON object, the value of a key is obtained, and whether a key exists is judged

front end vue When passing data of an object type to the backend , The front end first converts the object into json character string , And then pass it to the back end , At this point, the backend needs to parse this json Word string , And take out the corresponding attribute value .

1、JSON String to JSON object

import com.alibaba.fastjson.JSONObject;

String jsonStr = "{\"id\": 2," +
                " \"title\": \"json title\", " +
                "\"config\": {" +
                "\"width\": 34," +
                "\"height\": 35," +
                "}, \"data\": [" +
                "\"JAVA\", \"JavaScript\", \"PHP\"" +
                "]}";
// take json String to json object 
JSONObject jsonobj = JSONObject.parseObject(jsonStr);

2、 Get the value of a property

// there id yes json The key name of the object 
String value = jsonobj.getString("data");

3、 Judge a certain key Whether there is  

import com.alibaba.fastjson.JSONObject;

jsonobj.containsKey("message");    // If there is key be known as  "message" , return true; Otherwise return to false