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Subtle Changes in Java 8: Repeatable Annotations

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Subtle Changes in Java 8: Repeatable Annotations

· Java Zone
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Check out this 8-step guide to see how you can increase your productivity by skipping slow application redeploys and by implementing application profiling, as you code! Brought to you in partnership with ZeroTurnaround.

Apart from the “big stuff”, related to extension methodslambda, and the streams API, Java 8 also has a couple of minor, very subtle changes. One of them is the fact that you can now annotate an object several times with the same annotation!

An example taken from the tutorial:

@Alert(role="Manager")
@Alert(role="Administrator")
public class UnauthorizedAccessException { ... }

For this to work, your @Alert annotation has to be meta-annotated with java.lang.annotation.Repeatable.

Tools, which heavily rely on annotation processing might need to review their code to get ready for Java 8. Existing methods, such as AnnotatedElement.getAnnotations(), have not been retrofitted to return repeatable annotations. Instead, other, new methods, such as AnnotatedElement.getAnnotationsByType(Class) and AnnotatedElement.getDeclaredAnnotationsByType(Class) have been added to the JDK, in order to be able to discover repeated annotations on any element.

More authoritative information can be found here:

The Java Zone is brought to you in partnership with ZeroTurnaround. Check out this 8-step guide to see how you can increase your productivity by skipping slow application redeploys and by implementing application profiling, as you code!

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Published at DZone with permission of Lukas Eder, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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