* java8 新增的@Repeatable注解，其实只是语法糖而已．
* java8 注解的 {@link RepeatAnn} 类与 {@link Annotations}是等价的．
* 新注解讲语法糖转化为注解值为数组形式．
package com.github.jdk8.ebook.java8_recipes2nd_edition;
import java.lang.annotation.Annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Arrays;
/**
* java8 新增的@Repeatable注解，其实只是语法糖而已．
* java8 注解的 {@link RepeatAnn} 类与 {@link Annotations}是等价的．
* 新注解讲语法糖转化为注解值为数组形式．
* @author doctor
*
* @since 2015年2月3日 下午8:33:43
*/
public class Chapter2Code {
public static void main(String[] args) {
Annotation[] annotations = RepeatAnn.class.getAnnotations();
System.out.println(annotations.length); //1
Arrays.stream(annotations).forEach(System.out::println);//@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Roles(value=[@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=doctor), @com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=who)])
Annotation[] annotations2 = Annotations.class.getAnnotations();
System.out.println(annotations2.length);//1
Arrays.stream(annotations2).forEach(System.out::println);//@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Roles(value=[@com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=doctor), @com.github.jdk8.ebook.java8_recipes2nd_edition.Chapter2Code$Role(name=who)])
}
/**
* The same annotation can be applied to a declaration or type more than
* once, given that each annotation is marked as @Repeatable. In the
* following code, the @Repeatable annotation is used to develop an
* annotation that can be repeated, rather than grouped together as in
* previous releases of Java. In this situation, an annotation named Role is
* being created, and it will be used to signify a role for an annotated
* class or method.
*
* @author doctor
*
* @since 2015年2月3日 下午8:51:09
*/
@Repeatable(value = Roles.class)
public static @interface Role {
String name() default "doctor";
}
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public static @interface Roles {
Role[] value();
}
@Role(name = "doctor")
@Role(name = "who")
public static class RepeatAnn{
}
@Roles({@Role(name="doctor"),
@Role(name="who")})
public static class Annotations{
}
}
原文地址：http://blog.csdn.net/doctor_who2004/article/details/43457689
