Groovy: how to concatenate string constants in annotation?

Question

In java I can write @SomeAnnotation("abc"+"cd") . When I do the same in groovy i got compilation error 'expected ... to be an inline constant'. how can i concatenate string constants inside annotations in groovy?

Answer 1

You can't because this expression isn't a compile time constant in Groovy.

You have a few options here

• Declare a plain Java interface with constants and use it from Groovy

   @SomeAnnotation(Constants.MY_CONST) 

• If you can change source code of annotation you can try using closure annotation parameters

• You can also play with compile-time AST transformations here to achieve your goal in a dirty way. (Very probably you don't want to play with AST)

Inability to use expressions like 'aaa' + 'bbb' isn't the only problem, you can see errors like Attribute 'value' should have type 'java.lang.String'; but found type 'java.lang.Object' Attribute 'value' should have type 'java.lang.String'; but found type 'java.lang.Object' even with compile-time expressions. Here is a related issue GROOVY-3278 with possible workarounds.