spring笔记-@AliasFor

1.概念

@AliasFor注解可以为注解本身提供别名

2.配对别名

public class AliasForDemo {


    public static class TestBean
    {

        @AliasFor("test")
        public void test()
        {}
    }


    @Test
    public void test1() throws NoSuchMethodException {
        Method method=TestBean.class.getMethod("test",null);

        AliasFor aliasFor1=method.getAnnotation(AliasFor.class);
        AliasFor aliasFor2=AnnotationUtils.synthesizeAnnotation(aliasFor1,null);
        AliasFor aliasFor3=AnnotationUtils.getAnnotation(method,AliasFor.class);
    }

    @Test
    public void test2() throws NoSuchMethodException {

        ContextConfig contextConfig1 = SimpleConfigTestCase.class.getAnnotation(ContextConfig.class);
        ContextConfig contextConfig2=AnnotationUtils.synthesizeAnnotation(contextConfig1,null);
        ContextConfig contextConfig3=AnnotationUtils.getAnnotation(SimpleConfigTestCase.class,ContextConfig.class);
    }

    @ContextConfig("simple.xml")
    static class SimpleConfigTestCase {
    }

    @Retention(RetentionPolicy.RUNTIME)
    @interface ContextConfig {

        @AliasFor("location")
        String value() default "";

        @AliasFor("value")
        String location() default "";

        Class klass() default Object.class;
    }
}

输出结果:

可以看到,如果使用jdk内置方法获取注解是无法使用别名特性的,因为该特性是spring提供,所以可以调用AnnotationUtils.synthesizeAnnotation方法来获取一个动态代理注解
也可以直接调用AnnotationUtils.getAnnotation来获取注解,内部会调用AnnotationUtils.synthesizeAnnotation方法

参考:
https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/annotation/AliasFor.html
http://ifeve.com/annotation-programming-model/