How do I write a custom JSON deserializer for Gson?

by

I’d take a slightly different approach as follows, so as to minimize “manual” parsing in my code, as unnecessarily doing otherwise somewhat defeats the purpose of why I’d use an API like Gson in the first place.

// output:
// [User: id=1, name=Jonas, updateDate=2011-03-24 03:35:00.226]
// [User: id=5, name=Test, updateDate=2011-05-07 08:31:38.024]

// using java.sql.Timestamp

public class Foo
{
  static String jsonInput = 
    "[" +
      "{\"id\":1,\"name\":\"Jonas\",\"update_date\":\"1300962900226\"}," +
      "{\"id\":5,\"name\":\"Test\",\"update_date\":\"1304782298024\"}" +
    "]";

  public static void main(String[] args)
  {
    GsonBuilder gsonBuilder = new GsonBuilder();
    gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
    gsonBuilder.registerTypeAdapter(Timestamp.class, new TimestampDeserializer());
    Gson gson = gsonBuilder.create();
    User[] users = gson.fromJson(jsonInput, User[].class);
    for (User user : users)
    {
      System.out.println(user);
    }
  }
}

class User
{
  int id;
  String name;
  Timestamp updateDate;

  @Override
  public String toString()
  {
    return String.format(
      "[User: id=%1$d, name=%2$s, updateDate=%3$s]",
      id, name, updateDate);
  }
}

class TimestampDeserializer implements JsonDeserializer<Timestamp>
{
  @Override
  public Timestamp deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
      throws JsonParseException
  {
    long time = Long.parseLong(json.getAsString());
    return new Timestamp(time);
  }
}

(This assumes that “date_date” should be “update_date”, in the original question.)

More Related Contents:

  1. Polymorphism with gson
  2. Deserializing Generic Types with GSON
  3. How do I implement TypeAdapterFactory in Gson?
  4. Gson – deserialization to specific object type based on field value
  5. GSON does not deserialize reference to outer class
  6. How to handle a NumberFormatException with Gson in deserialization a JSON response
  7. Converting JSON data to Java object
  8. How to Parse JSON Array with Gson
  9. Gson serialize a list of polymorphic objects
  10. How to parse json parsing Using GSON in android
  11. Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2
  12. Jackson Vs. Gson [closed]
  13. Custom JSON deserializer using Gson
  14. How to decode JSON with unknown field using Gson?
  15. Using Enums while parsing JSON with GSON
  16. Convert Json date to java date
  17. How to parse dynamic JSON fields with GSON?
  18. Gson and deserializing an array of objects with arrays in it
  19. Right way to write JSON deserializer in Spring or extend it
  20. Deserializing an abstract class in Gson
  21. Gson: Directly convert String to JsonObject (no POJO)
  22. Trouble with Gson serializing an ArrayList of POJO’s
  23. Converting json string to java object?
  24. Gson Serialize field only if not null or not empty
  25. Make GSON accept single objects where it expects arrays
  26. how to parse a huge JSON file without loading it in memory
  27. How do I use Google’s Gson API to deserialize JSON properly?
  28. Can you avoid Gson converting “” into unicode escape sequences?
  29. How to compare JSON documents and return the differences with Jackson or Gson?
  30. Jackson JSON Deserialization: array elements in each line

Leave a Comment