code: public static Map<String, Object> toNullableMap(String value) {
  		if (value == null)
  			return null;
  
  		try {
  			Map<String, Object> map = _mapper.readValue((String) value, typeRef);
  			return RecursiveMapConverter.toNullableMap(map);
  		} catch (Exception ex) {
  			return null;
  		}
  	}
docs: Converts JSON string into map object or returns null when conversion is not
  possible.
  
  @param value the JSON string to convert.
  @return Map object value or null when conversion is not supported.
  
  @see MapConverter#toNullableMap(Object)