Over a million developers have joined DZone.
{{announcement.body}}
{{announcement.title}}

Subtle Changes in Java 8: Repeatable Annotations

DZone's Guide to

Subtle Changes in Java 8: Repeatable Annotations

· Java Zone ·
Free Resource

How do you break a Monolith into Microservices at Scale? This ebook shows strategies and techniques for building scalable and resilient microservices.

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:

How do you break a Monolith into Microservices at Scale? This ebook shows strategies and techniques for building scalable and resilient microservices.

Topics:

Published at DZone with permission of

Opinions expressed by DZone contributors are their own.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}