public class Annote {    @Retention(RetentionPolicy.RUNTIME)    @Target({ElementType.TYPE,ElementType.METHOD,ElementType.FIELD,ElementType.CONSTRUCTOR})    public @interface RequiredRoles{        String name();        int id() default 0;    }        @RequiredRoles(name="type") //类成员注解    public class UserAnnotation {                @RequiredRoles(name="param", id=1) //类成员注解        private Integer age;                @RequiredRoles (name="construct", id=2)//构造方法注解        public UserAnnotation(){        }                @RequiredRoles(name="public method", id=3) //类方法注解        public void a(){            Map m = new HashMap(0);        }                @RequiredRoles(name="protected method", id=4) //类方法注解        protected void b(){            Map m = new HashMap(0);        }                @RequiredRoles(name="private method", id=5) //类方法注解        private void c(){            Map m = new HashMap(0);        }    }        public static void parseTypeAnnotation() throws ClassNotFoundException {          Class clazz = Class.forName("Annote$UserAnnotation");                Annotation[] annotations = clazz.getAnnotations();                for (Annotation annotation : annotations) {              RequiredRoles testA = (RequiredRoles)annotation;            System.out.println("id= "+testA.id()+" name= "+testA.name());          }      }         public static void parseMethodAnnotation(){        Method[] methods = UserAnnotation.class.getDeclaredMethods();          for (Method method : methods) {                          boolean hasAnnotation = method.isAnnotationPresent(RequiredRoles.class);              if (hasAnnotation) {                                  RequiredRoles annotation = method.getAnnotation(RequiredRoles.class);                  System.out.println("method = " + method.getName()  + " ; id = " + annotation.id() + " ; description = "+ annotation.name());              }          }      }            public static void main(String[] args) throws ClassNotFoundException{        parseTypeAnnotation();                parseMethodAnnotation();    }    }

详细参考：http://blog.sina.com.cn/s/blog_93dc666c0101gzn5.html

 

1、注解本质是就是对类、属性、方法的注释 2、区别是，如果在声明注解的时候加上了 @Retention(RetentionPolicy.RUNTIME) 属性， 就可以在运行的时候通过代码读取到具体的注解内容，而注释在运行时是读取不到的

 

 

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