java RetentionPolicy CLASS 与 RUNTIME
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RetentionPolicy CLASS vs. RUNTIME
提问by Dima
What is the practical difference between RetentionPolicy.CLASSand RetentionPolicy.RUNTIME?
RetentionPolicy.CLASS和之间的实际区别是RetentionPolicy.RUNTIME什么？
It looks like both are recorded into the bytecode and both may be accessed at the run-time anyway.
看起来两者都记录在字节码中，无论如何都可以在运行时访问。
回答by skaffman
both may be accessed at the run-time anyway.
无论如何，两者都可以在运行时访问。
That's not what the javadocsays:
这不是javadoc所说的：
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.
RUNTIME：注解会被编译器记录在类文件中，并在运行时由VM保留，因此它们可以被反射读取。
CLASS: Annotations are to be recorded in the class file by the compiler but need not be retained by the VM at run time.
CLASS：注解将被编译器记录在类文件中，但不需要在运行时由 VM 保留。
In practice, I'm not aware of any use-cases for CLASS. It would only be useful if you wanted to read the bytecode programmatically, as opposed to via the classloader API, but that's a very specialised case, and I don't know why you wouldn't just use RUNTIME.
实际上，我不知道CLASS. 它仅在您想以编程方式读取字节码时才有用，而不是通过类加载器 API，但这是一个非常特殊的情况，我不知道您为什么不只使用RUNTIME.
Ironically, CLASSis the default behaviour.
具有讽刺意味的是，这CLASS是默认行为。
