I need to read a file from the file system and load the entire contents into a string in a groovy controller, what\'s the easiest way to do that?
The shortest way is indeed just
String fileContents = new File('/path/to/file').text
but in this case you have no control on how the bytes in the file are interpreted as characters. AFAIK groovy tries to guess the encoding here by looking at the file content.
If you want a specific character encoding you can specify a charset name with
String fileContents = new File('/path/to/file').getText('UTF-8')
See API docs on File.getText(String) for further reference.