分享程序员开发的那些事...
更新时间：2022-06-12 04:31:25
As you've discovered, you need to add @Retention(RUNTIME) to your composed annotation in order for JUnit to see it. Annotations in Java have three different retention policies:
注释将被编译器丢弃.
Annotations are to be discarded by the compiler.
RetentionPolicy.CLASS
注释由编译器记录在类文件中，但VM不必在运行时保留. 这是默认行为. [添加了重点]
RetentionPolicy.RUNTIME
注释由编译器记录在类文件中，并在运行时由VM保留，以便可以通过反射方式读取.
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.
如上所述，如果您未明确添加@Retention(...)，则会使用CLASS策略.这不适用于JUnit，因为JUnit不会扫描*.class文件(即字节码)中的注释，而是以反射方式扫描 loaded 类以找到测试方法.没有RUNTIME保留策略，您的注释将无法反射访问，因此JUnit永远不会看到它，因此不会执行测试.
As I emphasized above, if you don't explicitly add @Retention(...) then the CLASS policy is used. This won't work with JUnit because JUnit doesn't scan the *.class files (i.e. byte-code) for the annotations, it scans the loaded classes reflectively to find test methods. Without a RUNTIME retention policy your annotation is not reflectively accessible, thus JUnit never sees it and consequently doesn't execute the test.