withMandatoryParameter supports a error message from the caller

[marcusholl]

For some transport related steps it would be cool to have a message providing more details about what is going wrong.

[CCFenner]

I would suggest to make use of the SimpleTemplateEngine:

import groovy.text.SimpleTemplateEngine

def getMandatoryProperty(key, defaultValue = null, errorMessage = "ERROR - NO VALUE AVAILABLE FOR ${key}"){
  [...]
  errorMessage = SimpleTemplateEngine.newInstance()
    .createTemplate(errorMessage)
    .make([key: key]).toString()

  throw new IllegalArgumentException(errorMessage)

[marcusholl]

@CCFenner mmmhhhhhh ... Sounds like shooting on sparrows with cannons. Should we do that all the time we create a string containing a parameter? We have thousands of similar statements in the code using groovy strings for that. What is bad with the "good old" groovy string approach? Would make sense to use a template engine for big strings, like html templates where we have to replace variables with values when performance is an issue. But for a very simple and short string. What would be your general recommendation for using a TemplateEngine vs. using the groovy string pattern?

[CCFenner]

You are right, the key is handed in from the outside anyway...