Converting JSON Data to Java Object

I need some help with a specific issue I'm encountering.

I have retrieved a JSON string from MongoDB and I am trying to extract all the values of 'photo' and store them in an ArrayList. Despite finding examples online, I haven't been successful in making them work. I am currently using GSON for this task, but even a solution based on pure JSON would be acceptable.

The data returned from MongoDB is as follows:

  [ { "url" : "/photos/avatar-1.jpg" , "photo" : "avatar-1.jpg" , "description" : "test     1"} , { "url" : "/photos/avatar-2.jpg" , "photo" : "avatar-2.jpg" , "description" : "test 2"} , { "url" : "/photos/avatar-3.jpg" , "photo" : "avatar-3.jpg" , "description" : "test 3"} , { "url" : "/photos/avatar-4.jpg" , "photo" : "avatar-4.jpg" , "description" : "test 4"}]

Adding the values to an ArrayList isn't an issue, it's extracting the 'photo' value that's proving challenging. If anyone could provide me with a sample code that demonstrates how to iterate through the 4 arrays and print out the 'photo' value using System.out.println, I would greatly appreciate it!

Thank you!

javajsonobjectgson

Answer №1

jsonString = [...];
Gson gson = new Gson();
PhotoDTO[] photos = gson.fromJson(jsonString, PhotoDTO[].class);

for(PhotoDTO photo : photos){
   System.out.println("photo -> " + photo.getPhoto());
}

PhotoDTO Class Structure 

class PhotoDTO
{
  String url;
  String photo;
  String description;
  // methods for setting and getting values
}

Answer №2

To handle JSON data efficiently, consider utilizing the json-simple library available at this link. Here's an example of how you can use it:

String jsonData = "[{\"photo\": \"1.png\"}, {\"photo\": \"2.png\"}, " +
                "{\"photo\": \"3.png\"}, {\"photo\": \"4.png\"}]";
JSONArray photosArray = (JSONArray)JSONValue.parse(jsonData);
for (int i = 0; i < photosArray.size(); i++) {
    JSONObject photoObject = (JSONObject)photosArray.get(i);
    System.out.println(photoObject.get("photo"));
}

Remember to replace the hardcoded JSON text with the actual data retrieved from your database.

Answer №3

A different approach that eliminates the need to create DTOs involves utilizing the Gson library's StringMap class:

String json = "[ { \"url\" : \"/photos/avatar-1.jpg\" , \"photo\" : \"avatar-1.jpg\" , \"description\" : \"test     1\"} , { \"url\" : \"/photos/avatar-2.jpg\" , \"photo\" : \"avatar-2.jpg\" , \"description\" : \"test 2\"} , { \"url\" : \"/photos/avatar-3.jpg\" , \"photo\" : \"avatar-3.jpg\" , \"description\" : \"test 3\"} , { \"url\" : \"/photos/avatar-4.jpg\" , \"photo\" : \"avatar-4.jpg\" , \"description\" : \"test 4\"}]";   

Gson gson = new Gson();     
Type type = new TypeToken<List<StringMap<String>>>(){}.getType();
List<StringMap<String>> stringMaps = gson.fromJson(json, type);
for (StringMap<String> map:stringMaps) {
    System.out.println(map.get("photo"));
}

UPDATE

Required Imports:

import com.google.gson.Gson;
import com.google.gson.internal.StringMap;
import com.google.gson.reflect.TypeToken;

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