How to prevent Gson from converting a long number (a json string ) to scientific notation format?

Question

I need to convert json string to java object and display it as a long. The json string is a fixed array of long numbers:

{numbers
[ 268627104, 485677888, 506         


        

Answer 1

I had a similar problem, and it not only converts integers to double, but it actually loses precision for certain long numbers, as described in this related question.

I tracked down this conversion to ObjectTypeAdapter's read method, specifically:

case NUMBER:
  return in.nextDouble();

It may be possible to plug in a modified TypeAdapter for Object, but I couldn't get that to work, so instead I just copied the read method (Object read(JsonReader in)) to my own code and modified the above lines to this:

case NUMBER:
    final String s = in.nextString();
    try {
        return Integer.parseInt(s);
    } catch (NumberFormatException e) {
        // ignore
    }
    try {
        return Long.parseLong(s);
    } catch (NumberFormatException e) {
        // ignore
    }
    return Double.parseDouble(s);

I wish Gson did this by default..

Then I put the other connecting pieces in a helper method that looks something like this:

public static Object parse(final Reader r) {
    try (final JsonReader jr = new JsonReader(r)) {
        jr.setLenient(true);
        boolean empty = true;
        Object o = null;
        try {
            jr.peek();
            empty = false;
            o = read(jr);
        } catch (EOFException e) {
            if (!empty) {
                throw new JsonSyntaxException(e);
            }
        }
        if (o != null && jr.peek() != JsonToken.END_DOCUMENT) {
            throw new JsonIOException("JSON document was not fully consumed.");
        }
        return o;
    } catch (IOException e) {
        throw new JsonIOException(e);
    }
}

So now instead of new Gson().fromJson(r, Object.class), I call parse(r).

This works well for me because I want to be able to parse json data with any structure, but if you have a particular class you're targeting, you probably just need to eliminate occurrences of Object within that class's members.