best (or at least good) guide to Java annotations

Question

There must be a good book/PDF/HTML file that describes the essentials & good practices of annotations in Java. I sort of know what they are from other good Java books, but I'm looking for something that would teach me most of what I would need to know to make good use of them. (preferably in PDF/HTML so I can print it out & read at my leisure, book ok also but those go out of date so fast...)

Any recommendations?

edit: I found the Sun guides, as well as tutorials like these from O'Reilly and DevX, and the section of Effective Java that covers them... OK, so I know what they are and what tools to read them, but that doesn't tell me much about how they are put to use in practice. (other than a little bit in Effective Java and the O'Reilly article above that suggest their use in automated testing frameworks)

Answer 1

http://java.sun.com/j2se/1.5.0/docs/guide/language/annotations.html and http://java.sun.com/docs/books/tutorial/java/javaOO/annotations.html have basically everything I've needed.

Answer 2

For annotation processing, I'd suggest Getting Started with apt. Also see the Javadocs at http://java.sun.com/javase/6/docs/api/javax/annotation/processing/package-summary.html and http://java.sun.com/javase/6/docs/api/javax/lang/model/element/package-summary.html.

Answer 3

Some opinions on annotations: http://faler.wordpress.com/2007/11/21/when-to-use-and-not-to-use-java-annotations/

This guy is very much against them: http://www.softwarereality.com/programming/annotations.jsp

Best Practices: http://willcode4beer.com/opinion.jsp?set=annotations_gotchas_best_practices

Hope this helps. Let us know what you find.