In Java, it's possible to pass a constant String as a parameter to an annotation, but I can't figure out how to do the same in Groovy.
For example:
@Retention(RetentionPolicy.RUNTIME) @Target(value=[ElementType.METHOD]) public @interface MyGroovyAnnotation { String value() } class MyGroovyClass { public static final String VALUE = "Something" @MyGroovyAnnotation(value=VALUE) public String myMethod(String value) { return value } }
Here, where the method myMethod
is annotated with @MyGroovyAnnotation
, if I pass a String literal like @MyGroovyAnnotation(value="Something")
, it works perfectly, but if I try to pass VALUE
like in the example above, I get:
From Eclipse:
Groovy:Expected 'VALUE' to be an inline constant of type java.lang.String in @MyGroovyAnnotation
Running from GroovyConsole:
expected 'VALUE' to be an inline constant of type java.lang.String not a field expression in @MyGroovyAnnotation at line: 20, column: 31 Attribute 'value' should have type 'java.lang.String'; but found type 'java.lang.Object' in @MyGroovyAnnotation at line: -1, column: -1
Does anybody have any idea what I need to do to get this to work, or if it's even possible? Thanks for any help or insight you can provide.
if the compiler expects an "Array Initializer" to be passed to the Annotation, declaring a compile-time constant like private static final String[] AB = { ... }; should do. it's understood that Annotation processing happens before the actual compilation, but then the error message is not accurate.
Advertisements. Annotations are a form of metadata wherein they provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate.
groovy Groovy Truth (true-ness)Groovy evaluates conditions in if, while and for statements the same way as Java does for standard Java conditions : in Java you must provide a boolean expression (an expression that evaluates to a boolean) and the result is the result of the evaluation.
I ran into this same issue and Gerard's answer works, but I didn't need to make a new Constants class, just refer to the existing class.
For example:
@Retention(RetentionPolicy.RUNTIME) @Target(value=[ElementType.METHOD]) public @interface MyGroovyAnnotation { String value() } class MyGroovyClass { public static final String VALUE = "Something" @MyGroovyAnnotation(value=MyGroovyClass.VALUE) public String myMethod(String value) { return value } }
I wanted to leave a comment on the accepted answer, but I didn't have 50 reputation.
The question that's suggested as similar here (accessing-static-field-in-annotation), is different to this, as the answer there was to make the String final, which is already the case here. I've gotten a way to make this work, so I guess it's best that I answer here for others with the same question! :)
The above code doesn't work, but specifying the String to pass to the annotation as a field in another class works fine, oddly enough:
Retention(RetentionPolicy.RUNTIME) @Target(value=[ElementType.METHOD]) public @interface MyGroovyAnnotation { String value() } class Constants { public static final String VALUE = "Something" } public class MyGroovyClass { @MyGroovyAnnotation(value=Constants.VALUE) public String myMethod(String value) { return value } }
I'm not sure exactly why one of these situations works and the other doesn't. Reading the comments in the bug mentioned in the aforementioned similar question, it seems that the Groovy developers ran into problems covering all cases that Java covers with respect to passing constant String references as annotation parameters.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With