Gson converting any integer to 0 when using fromJson

Question

This is the POJO:

public class MyPojo {
  String id;
  double myNumber;
}

This is my JSON:

{
    "id": "id1",
    "my_number": 10.0
}

This is my conversion code:

// from is the JSON String from Above
Map<String, Object> myData = gson.fromJson(new String(from, StandardCharsets.UTF_8), Map.class);
JsonElement jsonElement = gson.toJsonTree(myData);  // I checked - this contains "myNumber: 10"
MyPojo pojo = gson.fromJson(jsonElement, MyPojo.class);  // This contains "myNumber: 0"

myNumber in the pojo object is always 0

In my json I renamed it to myNumber and that didn't work either.

Why is this happening and how do I fix it so that I don't lose the value of the int? Thanks

Answer 1

my_number is not equal to myNumber – meaning that the mapping is not correct in your case. You either have to configure the JSON name in the POJO (there is an annotation for that – @SerializedName), or you have to change the name of the attribute.

I prefer the first approach, so you change the POJO like this:

public final class MyPojo 
{
  String id;

  @SerializedName( "my_number" )
  double myNumber;
}