深入理解Java注解的使用方法

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.METHOD})
@Inherited
public @interface AnnoInherited {
  
}

public class TestAnnoInherated {
  public static void main(String[] args) {
    Annotation[] annos=new Goo().getClass().getAnnotations();
    for(Annotation a:annos){
      System.out.println(a);
    }
  }
}

@AnnoInherited
class Foo{
  
}

class Goo extends Foo{
  
}  

package test.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AnimalInfo {
  String shout() default "";
  
  //能不能看门
  boolean isGuard() default true;
}

public class TestAnimalInfo {
  public static void main(String[] args) {
    Animal animal=new Animal();
    AnimalInfo info=animal.getClass().getAnnotation(AnimalInfo.class);
    if(info!=null){
      Annotation anno=info;//此处并没有报错.Annotation是一个接口.info是一个注解.这是因为编译器会将注解编译成接口,并且继承了Annotation
      System.out.println("Annotation类信息:"+Annotation.class);
      System.out.println("AnimalInfo类信息:"+AnimalInfo.class);
      Class[] cs=AnimalInfo.class.getInterfaces();
      for(Class c:cs){
        System.out.println(c); //AnimalInfo编译后就是一个接口,并且继承了Annotation,这里得到了证实.
      }
      System.out.println("info对象的类信息:"+info.getClass());
      if("wangwang".equals(info.shout())&&info.isGuard()){
        System.out.println("the animal is a dog");
      }else if("miaomiao".equals(info.shout())&&!info.isGuard()){
        System.out.println("the animal is a cat");
      }else{
        System.out.println("the animal is not a dog or cat");
      }
    }else{
      System.out.println("it's not a animal");
    }
  }
}

@AnimalInfo(shout="wangwang",isGuard=true)
class Animal{
  
}

Annotation类信息:interface java.lang.annotation.Annotation
AnimalInfo类信息:interface test.annotation.AnimalInfo
interface java.lang.annotation.Annotation
info对象的类信息:class com.sun.proxy.$Proxy1
the animal is a dog