Evaluate Java 8 repeatable annotations [SPR-10532]

[spring-projects-issues]

Juergen Hoeller opened SPR-10532 and commented

http://docs.oracle.com/javase/tutorial/java/annotations/repeating.html

We should be able to use @Repeatable without backwards compatibility issues, since unknown annotations will be ignored by the JVM at runtime.

Identifying Spring annotations that are actually repeatable according to their semantics is an important part of this exercise (e.g. @Scheduled).

Since @Repeatable requires implicit container annotations anyway, we should be able to provide those in a way that works on Java 6 and 7 as well.

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This issue is a sub-task of #14273

1 votes, 4 watchers

[spring-projects-issues]

Juergen Hoeller commented

Implemented for @Scheduled at the moment, with @Schedules as a Java 8 compliant container annotation that is also usable on Java 6 and 7.

@Caching, as an existing container-style annotation, allows for combining several kinds of operation annotations. This doesn't seem to translate well to the Java 8 repeatable annotation mechanism which is only focused on repetition of one specific annotation, so @Caching remains as-is for the time being.

Another candidate might be @RequestMapping, although it's less clear what the use case there is. The interaction with parameter-level annotations also suggests that a @RequestMapping specification should rather remain unique.

Juergen

[spring-projects-issues]

Stefan Gheorghiu commented

Scala 2.10 compiler fails to compile a class with a method annotated with @Scheduled on JDK version less than 8, just because it cannot find the java.lang.annotation.Repeatable class. As a workaround, I had to create a dummy @Repeatable annotation in my codebase for Java 7.