How do different retention policies affect my annotations?

java annotations
xdevel2000 picture xdevel2000 · Jun 24, 2010 · Viewed 60k times · Source

Can anyone explain in a clear way the practical differences between the java.lang.annotation.RetentionPolicy constants SOURCE, CLASS, and RUNTIME?

I'm also not exactly sure what the phrase "retaining annotation" means.

Answer

Favonius picture Favonius · Jun 24, 2010

  • RetentionPolicy.SOURCE: Discard during the compile. These annotations don't make any sense after the compile has completed, so they aren't written to the bytecode.
    Example: @Override, @SuppressWarnings

  • RetentionPolicy.CLASS: Discard during class load. Useful when doing bytecode-level post-processing. Somewhat surprisingly, this is the default.

  • RetentionPolicy.RUNTIME: Do not discard. The annotation should be available for reflection at runtime. Example: @Deprecated

Source: The old URL is dead now hunter_meta and replaced with hunter-meta-2-098036. In case even this goes down, I am uploading the image of the page.

Image (Right Click and Select 'Open Image in New Tab/Window') Screenshot of Oracle website

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