Gson NumberFormatException

Question

If I try to deserialize my json:

String myjson = "

      {
       "intIdfCuenta":"4720",
       "intIdfSubcuenta":"0",
       "floatImporte":"5,2",
       "strSigno":"D",
       "strIdfClave":"FT",
       "strDocumento":"1",
       "strDocumentoReferencia":"",
       "strAmpliacion":"",
       "strIdfTipoExtension":"IS",
       "id":"3"
      }";


viewLineaAsiento asiento =  gson.fromJson(formpla.getViewlineaasiento(),viewLineaAsiento.class);        

I get this error:

com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: For input string: "5,2"

How can I parse "5,2" to Double???

I know that if I use "floatImporte":"5.2" I can parse it without any problem but I what to parse "floatImporte":"5,2"

Answer 1

Your JSON is in first place bad. You shouldn't be representing numbers as strings at all. You should basically either have all String properties in your ViewLineaAsiento Java bean object representation as well, or to remove those doublequotes from JSON properties which represent numbers (and fix the fraction separator to be . instead of ,).

If you're absolutely posisive that you want to continue using this bad JSON and fix the problem by a workaround/hack instead of fixing the problem by its roots, then you'd need to create a custom Gson deserializer. Here's a kickoff example:

public static class BadDoubleDeserializer implements JsonDeserializer<Double> {

    @Override
    public Double deserialize(JsonElement element, Type type, JsonDeserializationContext context) throws JsonParseException {
        try {
            return Double.parseDouble(element.getAsString().replace(',', '.'));
        } catch (NumberFormatException e) {
            throw new JsonParseException(e);
        }
    }

}

You can register it via GsonBuilder#registerTypeAdapter() as follows:

Gson gson = new GsonBuilder().registerTypeAdapter(Double.class, new BadDoubleDeserializer()).create();
ViewLineaAsiento asiento = gson.fromJson(myjson, ViewLineaAsiento.class);