Annotation retention policy: what real benefit is there in declaring `SOURCE` or `CLASS`?
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watery
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Published on 2014-08-22T16:40:59Z
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2014/08/25
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I know there are three retention policies for Java annotations:
CLASS: Annotations are to be recorded in the class file by the compiler but need not be retained by the VM at run time.
RUNTIME: Annotations are to be recorded in the class file by the compiler and retained by the VM at run time, so they may be read reflectively.
SOURCE: Annotations are to be discarded by the compiler.
And although I understand their usage scenarios, I don't get why it is such an important thing to specify the retention policy that retention policies exist at all.
I mean, why aren't all the annotations just kept at runtime? Do they generate so much bytecode / occupy so much memory that stripping those undeclared as RUNTIME does make that much difference?
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