}
// register built-in serializers
variableSerializers.addSerializer(new NullValueSerializer());
variableSerializers.addSerializer(new StringValueSerializer());
variableSerializers.addSerializer(new BooleanValueSerializer());
variableSerializers.addSerializer(new ShortValueSerializer());
variableSerializers.addSerializer(new IntegerValueSerializer());
variableSerializers.addSerializer(new LongValueSerlializer());
variableSerializers.addSerializer(new DateValueSerializer());
variableSerializers.addSerializer(new DoubleValueSerializer());