How to handle a NumberFormatException with Gson in deserialization a JSON response

Question

I'm reading a JSON response with Gson, which returns somtimes a NumberFormatException because an expected int value is set to an empty string. Now I'm wondering what's the best way to handle this kind of exception. If the value is an empty string, the deserialization should be 0.

Expected JSON response:

{
   "name" : "Test1",
   "runtime" : 90
}

But sometimes the runtime is an empty string:

{
   "name" : "Test2",
   "runtime" : ""
}

The java class looks like this:

public class Foo
{
    private String name;
    private int runtime;
}

And the deserialization is this:

String input = "{\n" +
               "   \"name\" : \"Test\",\n" +
               "   \"runtime\" : \"\"\n" +
               "}";

Gson gson = new Gson();
Foo foo = gson.fromJson(input, Foo.class);

Which throws a com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: empty String because an empty String is returned instead of an int value.

Is there a way to tell Gson, "if you deserialize the field runtime of the Type Foo and there is a NumberFormatException, just return the default value 0"?

My workaround is to use a String as the Type of the runtime field instead of int, but maybe there is a better way to handle such errors.

Answer 1

Here is example I did for Long type.This is better option:

    public class LongTypeAdapter extends TypeAdapter<Long>{
    @Override
    public Long read(JsonReader reader) throws IOException {
        if(reader.peek() == JsonToken.NULL){
            reader.nextNull();
            return null;
        }
        String stringValue = reader.nextString();
        try{
            Long value = Long.valueOf(stringValue);
            return value;
        }catch(NumberFormatException e){
            return null;
        }
    }
    @Override
    public void write(JsonWriter writer, Long value) throws IOException {
        if (value == null) {
            writer.nullValue();
            return;
        }
        writer.value(value);
    }
}

Register the adapter upon creation of the gson util:

Gson gson = new GsonBuilder().registerTypeAdapter(Long.class, new LongTypeAdapter()).create();

You can refer to this link for more.