JSON Arrays In Java

Question

So I'm looking to add a lot of users to a group messaging app that allows http post requests and I'm going to try to use the file upload function to read from a JSON but I'm a little confused as to how to write this in java:

{
  "members": [
    {
      "nickname": "Mom",
      "user_id": "1234567890",
      "guid": "GUID-1"
    },
    {
      "nickname": "Dad",
      "phone_number": "+1 2123001234",
      "guid": "GUID-2"
    },
    {
      "nickname": "Jane",
      "email": "[email protected]",
      "guid": "GUID-3"
    }
  ]
}

This is an exmaple of the JSON file that I need to write to, can someone explain how to write that in Java? (It would need nickname & phone_number fields, only those two per person) Thanks!

EDIT 1: Sorry, wasn't clear. I need to use Java to produce a file with these contents.

you just need a small method that takes the nickname, and number as function parameters and then appends them to a JSON file in the correct format. just like you would write to a text file. — James
– James, Commented Aug 19, 2015 at 16:30
Are you trying to create such a json from Java or you want to model this in Java? — Swapnil
– Swapnil, Commented Aug 19, 2015 at 16:30

Dezigo · Accepted Answer · 2015-08-19 16:33:01Z

3

Try try https://github.com/google/gson

http://www.studytrails.com/java/json/java-google-json-parse-json-to-java.jsp

Example:

import com.google.gson.Gson;

public class JavaToJsonAndBack {

    public static void main(String[] args) {
        Albums albums = new Albums();
        albums.title = "Free Music Archive - Albums";
        albums.message = "";
        albums.total = "11259";
        albums.total_pages = 2252;
        albums.page = 1;
        albums.limit = "5";
        GsonBuilder builder = new GsonBuilder();
        Gson gson = builder.create();
        System.out.println(gson.toJson(albums));

    }
}

This is how the resulting JSON looks like

{"title":"Free Music Archive - Albums","message":"","errors":[],
"total":"11259","total_pages":2252,"page":1,"limit":"5"}

answered Aug 19, 2015 at 16:33

Dezigo

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Skarllot · Accepted Answer · 2015-08-19 16:42:17Z

1

Treat {} as classes and [] as arrays:

import com.google.gson.annotations.SerializedName;

public class Message {
    @SerializedName("members")
    private List<Member> members;
...

public class Member {
    @SerializedName("nickname")
    private String nickname;
    @SerializedName("user_id")
    private String userId;
    @SerializedName("guid")
    private String guid;
...

To transform to JSON:

Message msg;
...
String jsonResult = new Gson().toJson(msg);

To get back from JSON:

Message msg = new Gson().fromJson(jsonStr, Message.class);

User guide: https://sites.google.com/site/gson/gson-user-guide

edited Aug 19, 2015 at 16:42

answered Aug 19, 2015 at 16:35

Skarllot

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