Java parse JSON array from JSON file

Question

I haven't been programming for a long time but I like it and trying to get back on track. So please excuse the nature of the problem/question here.

What I need is pretty simple in my opinion but i'm mostly struggling with using gson and json-simple to read my json file, one at a time, and be able to retrieve the values.

I have seen many approaches on here but as I said been a while and I have not done Java a lot in my career. So need some guidance/explanation on the best approach.

JSON:

[{ "car": "Toyota", "colour": "red", "qty": "1","date_manufactured":"12972632260006" }, { "car": "Hyundai", "colour": "red", "qty": "2","date_manufactured":"1360421626000" }, { "car": "Kia", "colour": "blue", "qty": "2", "date_manufactured":"1265727226000"}, ]

Any help to put me on the right track is appreciated!

Answer 1

1. Create a POJO class to represent your JSON data:

   public class CarInfo {  
     String car;
     String colour;
     String qty;
     String date_manufactured; 
   }
   

2. Use GSON to parse JSON String Array

   String carInfoJson = "[{ \"car\": \"Toyota\", \"colour\": \"red\",\"qty\": \"1\",\"date_manufactured\":\"12972632260006\" }, { \"car\":\"Hyundai\", \"colour\":\"red\",\"qty\":\"2\",\"date_manufactured\":\"1360421626000\" }]";
   Gson gson = new Gson();  
   CarInfo[] carInfoArray = gson.fromJson(carInfoJson, CarInfo[].class);  
   

3. Use GSON to parse JSON String Array from a file

   String carInfoJson= new String(Files.readAllBytes(Paths.get("filename.txt")));
   Gson gson = new Gson();  
   CarInfo[] carInfoArray = gson.fromJson(carInfoJson, CarInfo[].class);
   

4. Use GSON to parse JSON String Array from a file using BufferedReader

   BufferedReader reader = null;
   try {
     reader = new BufferedReader(new FileReader(file));
     Gson gson = new Gson(); 
     CarInfo[] carInfoArray = gson.fromJson(reader, CarInfo[].class);
   } catch (FileNotFoundException ex) {
     ...
   } finally {
     ...
   }
   

5. Use GSON to parse JSON String Array from a file using JsonReader in stream mode

   try {
     InputStream stream = new FileInputStream("c:\\filename.txt");
     JsonReader reader = new JsonReader(new InputStreamReader(stream, "UTF-8"));
     Gson gson = new Gson();
   
     // Read file in stream mode
     reader.beginArray();
     while (reader.hasNext()) {
       CarInfo carInfo = gson.fromJson(reader, CarInfo.class);
     }
     reader.endArray();
     reader.close();
   } catch (UnsupportedEncodingException ex) {
     ...
   } catch (IOException ex) {
     ...
   }