Before decoding, you may need to pre-process the string data value. An example of this is when the source data has some characters not supported by the locale configuration on Numeric Decoding, such as the numeric value 876592.00 being represented as 876_592!00. To decode this value as (for instance) a double value, delete the underscore and replace the exclamation mark with a full-stop. You can specify a valuePreprocess decodeParam, which is a simple expression that you can applied to the String value before decoding it.