code: public static String toJson(Object value) throws JsonProcessingException {
  		if (value == null)
  			return null;
  		return _mapper.writeValueAsString(value);
  	}
docs: Converts value into JSON string.
  
  @param value the value to convert.
  @return JSON string or null when value is null.
  @throws JsonProcessingException when conversion fails for any reason.