Deserialise json in apex

Question

How to deserialize the below json ? I want to retrieve messages only in list of string .

{
"posts": {
"data": [
  {
    "message": "Hello. My name is sdfd. How can I help you?",
    "created_time": "2016-11-16T06:45:52+0000",
    "id": "1832195760359548_1832134398493692608"
  },
  {
    "message": "Hi,welcome to ddd.",
    "created_time": "2016-11-16T06:40:56+0000",
    "id": "1832195760359548_18321978373423026007"
  },
  {
    "story": "kjkj updated their profile picture.",
    "created_time": "2016-11-16T06:37:32+0000",
    "id": "18321957603594344548_1832197183692739"
  }
],
"paging": {
  "previous": "https://graph.facebook.com/v2.8/183219576034559548/posts?since=1479278752&access_token=EAACEdEose0cBABWmn8IwQkAhA34Il5eO5BvBonlKXnt7cPz2LAwnxXDSTSLgkaWL1CxCAyYZAjrHUQZBqC20wL9R7NuW7Mnrc3ZBMEwVjdfdf2W2PQMM1a2Y46lfNwxZBRQX7j5exZBHPNazan7uGsc3T3Qi7CZBlffRjvuig4KgC0k3OzVIIyeIGM&limit=25&__paging_token=enc_AdBdMzcB2oGURgtG7wm2L89Qhb5se42mxZAQvklD1fAZC5MlGYZAD1ZCbVceMDveZBmEOjVWrbvMxmPbAiDSdUfOOlvanZAW4RnByhuI0Ouw8ZASWZCDRQZDZD&__previous=1",
  "next": "https://graph.facebook.com/v2.8/183219576034559548/posts?access_token=EAACEdEose0cBABWmn8IwQkAhA34Il5eO5BvBonlKXnfdfdft7cPz2LAwnxXDSTSLgkaWL1CxCAyYZAjrHUQZBqC20wL9R7NuW7Mnrc3ZBMEwVj2W2PQMM1a2Y46lfNwxZBRQX7j5exZBHPNazan7uGsc3T3Qi7CZBlffRjvuig4KgC0k3OzVIIyeIGM&limit=25&until=1479278252&__paging_token=enc_AdBPW0qUekoNQXqvPa1dXT2I6piNQvU2EaaIKmMpzgXZAZAszw2esNJCEZCAgtEWxBMH369YEdvkmvHZBMEJZB05ef5GRf9cQ2wBtZAjcurKr9oLIobgZDZD"
 }
},    

"id": "1832195760359548"
}

Answer 1

You could use a JSONParser and iterate through the Tokens plucking out the "message" values...

list<string> messageList = new list<String>();
JSONParser parser = JSON.createParser(JSONContent);
// Advance to the next token.
while (parser.nextToken() != null) {
    System.debug('Current token: ' +  parser.getCurrentName());
    if(parser.getCurrentName() == 'message'){
        parser.nextToken();    //We want the value, so advance to the next token.
        messageList.add(parser.getText());
    }
}
system.debug(messageList);

This pattern, while not terribly efficient, provides a loosely typed solution that won't require code changes if the structure of the input JSON changes.

Answer 2

There is one good tool available. JSON2Apex

Using that you can generate a class and using that wrapper class you can get the data.

//
// Generated by JSON2Apex http://json2apex.herokuapp.com/
//

public class JSON2Apex {

    public Posts posts;
    public String id;

    public class Paging {
        public String previous;
        public String next;
    }

    public class Posts {
        public List<Data> data;
        public Paging paging;
    }

    public class Data {
        public String message;
        public String created_time;
        public String id;
        public String story;
    }


    public static JSON2Apex parse(String json) {
        return (JSON2Apex) System.JSON.deserialize(json, JSON2Apex.class);
    }
}

Now parse your JSON in parse method and it will give you JSON2Apex instance and from that you can easily get data (message or any other value) from this.