实例详解Java 自定义注解及利用反射读取注解

package com.java.annotation;

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

@Target({ElementType.METHOD,ElementType.TYPE})
@Inherited
@Documented
@Retention(RetentionPolicy.RUNTIME)
public @interface Annotation_my {
 
 String name() default "张三";//defalt 表示默认值
 
 String say() default "hello world";
 
 int age() default 21;
 
}

package com.java.annotation;

@Annotation_my //使用我们刚才定义的注解
public interface Person {
 
 @Annotation_my
 public void name();
 
 @Annotation_my
 public void say();
 
 @Annotation_my
 public void age();

}

package com.java.annotation;

@Annotation_my
@SuppressWarnings("unused")
public class Student implements Person {
 
 private String name;

 @Override
 @Annotation_my(name="流氓公子") //赋值给name 默认的为张三
//在定义注解时没有给定默认值时，在此处必须name赋初值
 public void name() {
  
 }


 @Override
 @Annotation_my(say=" hello world ！")
 public void say() {
  
 }

 @Override
 @Annotation_my(age=20)
 public void age() {
  
 }
}

package com.java.annotation;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class Text {
 Annotation[] annotation = null;

 public static void main(String[] args) throws ClassNotFoundException {
  new Text().getAnnotation();
 }
 
 public void getAnnotation() throws ClassNotFoundException{
  Class<?> stu = Class.forName("com.java.annotation.Student");//静态加载类
  boolean isEmpty = stu.isAnnotationPresent(com.java.annotation.Annotation_my.class);//判断stu是不是使用了我们刚才定义的注解接口if(isEmpty){
   annotation = stu.getAnnotations();//获取注解接口中的
   for(Annotation a:annotation){
    Annotation_my my = (Annotation_my)a;//强制转换成Annotation_my类型
    System.out.println(stu+":\n"+my.name()+" say: "+my.say()+" my age: "+my.age());
   }
  }
  Method[] method = stu.getMethods();//
  System.out.println("Method");
  for(Method m:method){
   boolean ismEmpty = m.isAnnotationPresent(com.java.annotation.Annotation_my.class);
   if(ismEmpty){
    Annotation[] aa = m.getAnnotations();
    for(Annotation a:aa){
     Annotation_my an = (Annotation_my)a;
     System.out.println(m+":\n"+an.name()+" say: "+an.say()+" my age: "+an.age());
    }
   }
  }
  //get Fields by force
  System.out.println("get Fileds by force !");
  Field[] field = stu.getDeclaredFields();
  for(Field f:field){
   f.setAccessible(true);
   System.out.println(f.getName());
  }
  System.out.println("get methods in interfaces !");
  Class<?> interfaces[] = stu.getInterfaces();
  for(Class<?> c:interfaces){
   Method[] imethod = c.getMethods();
   for(Method m:imethod){
    System.out.println(m.getName());
   }
  }
 }

}