如何获取类注解的java吗？ [英] How to get class annotation in java?

问题描述

我已经创建了自己的注释类型是这样的：

I have created my own annotation type like this:

public @interface NewAnnotationType {}

和它连接到一个类：

@NewAnnotationType
public class NewClass {
    public void DoSomething() {}
}

和我想通过这样的反射来获取类注解：

and I tried to get the class annotation via reflection like this :

Class newClass = NewClass.class;

for (Annotation annotation : newClass.getDeclaredAnnotations()) {
    System.out.println(annotation.toString());
}

但它不打印任何东西。我在做什么错了？

but it's not printing anything. What am I doing wrong?

推荐答案

默认保留策略是<一个href=\"http://docs.oracle.com/javase/7/docs/api/java/lang/annotation/RetentionPolicy.html#CLASS\"><$c$c>RetentionPolicy.CLASS这意味着，在默认情况下，注释信息在运行时没有保留：

The default retention policy is RetentionPolicy.CLASS which means that, by default, annotation information is not retained at runtime:

注解是要记录在由编译器在类文件中，但不一定由VM在运行时被保留。这是默认的行为。

Annotations are to be recorded in the class file by the compiler but need not be retained by the VM at run time. This is the default behavior.

相反，使用<一个href=\"http://docs.oracle.com/javase/7/docs/api/java/lang/annotation/RetentionPolicy.html#RUNTIME\"><$c$c>RetentionPolicy.RUNTIME:

注解要被记录在由编译器的类文件，并在运行时由VM保留，所以它们可以被反射性地读取。

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.

...您指定使用<$c$c>@Retention元注释：

...which you specify using the @Retention meta-annotation:

@Retention(RetentionPolicy.RUNTIME)
public @interface NewAnnotationType {
}

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