1. 概述
1.2 简介
Java 8 对注解处理提供了两点改进，可重复的注解及可用于类型的注解
2. 重复注解
要想定义重复注解，必须给它定义的容器类，还要使用 @Repeatable 注解修饰一下
@Repeatable(RepetitionAnnotations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface RepetitionAnnotation {
String value() default “ling”;
}
/**
* 容器类
*/
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface RepetitionAnnotations {
RepetitionAnnotation[] value();
}
测试方法
public class AnnotationTest {
@Test
public void t1() throws Exception {
Class<AnnotationTest> clazz = AnnotationTest.class;
Method method = clazz.getMethod(“show”);
// 获取方法上的注解
RepetitionAnnotation[] ras = method.getAnnotationsByType(RepetitionAnnotation.class);
for (RepetitionAnnotation repetitionAnnotation : ras) {
System.out.println(repetitionAnnotation.value());
}
}
@RepetitionAnnotation(“Hello”)
@RepetitionAnnotation(“World”)
public void show() {
}
}
3. 类型注解
就是向 @Target 添加一种类型 TYPE_PARAMETER
@Repeatable(RepetitionAnnotations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE,TYPE_PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface RepetitionAnnotation {
String value() default “ling”;
}
使用
@RepetitionAnnotation(“Hello”)
@RepetitionAnnotation(“World”)
public void show(@RepetitionAnnotation String str) {
}
本文首发于凌风博客：Java 8 重复注解与类型注解作者：凌风