Spring Support multiple aliases via @AliasFor

Previously, one annotation attribute only supported one alias. You can only do like this:

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Test1 {
        String test1() default "test1";
    }

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Test2 {
        String test2() default "test2";
    }

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Test1
    @Test2
    public @interface Test3 {

        @AliasFor(annotation = Test1.class, attribute = "test1")
        String test3() default "test3";

        @AliasFor(annotation = Test2.class, attribute = "test2")
        String test4() default "test4";
    }

But now, you can do this more easily:

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Test1
    @Test2
    public @interface Test3 {

        @AliasFor(annotation = Test1.class, attribute = "test1")
        @AliasFor(annotation = Test2.class, attribute = "test2")
        String test3() default "test3";
    }

Moreover, the mutual aliasing of different attributes in the same annotation can break the original limitation (although this kind of use scenario is less):

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Test4 {

        @AliasFor("test2")
        @AliasFor("test3")
        String test1() default "test";

        @AliasFor("test1")
        @AliasFor("test3")
        String test2() default "test";

        @AliasFor("test1")
        @AliasFor("test2")
        String test3() default "test";
    }

Combine examples above, you can use @AliasFor like this:

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Test5 {

        @AliasFor("test2")
        @AliasFor("test3")
        String test1() default "test1";

        @AliasFor("test1")
        @AliasFor("test3")
        String test2() default "test1";

        @AliasFor("test1")
        @AliasFor("test2")
        String test3() default "test1";
    }

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Test5
    public @interface Test6 {

        @AliasFor("test2")
        @AliasFor("test3")
        String test1() default "test2";

        @AliasFor("test1")
        @AliasFor("test3")
        String test2() default "test2";

        @AliasFor(annotation = Test5.class)
        @AliasFor("test1")
        @AliasFor("test2")
        String test3() default "test2";
    }

    @Target({ElementType.ANNOTATION_TYPE, ElementType.FIELD, ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Test6
    public @interface Test7 {

        @AliasFor(annotation = Test6.class)
        String test3() default "test3";
    }

    @Test7(test3 = "override the method")
    public static class Element4 {
    }

    @Test
    public void test3() {
        Test5 test5 = AnnotatedElementUtils.getMergedAnnotation(Element4.class, Test5.class);
        Test6 test6 = AnnotatedElementUtils.getMergedAnnotation(Element4.class, Test6.class);
        System.out.println(test5.toString());
        System.out.println(test6.toString());
        assertEquals("override the method", test6.test1());
        assertEquals("override the method", test6.test2());
        assertEquals("override the method", test6.test3());
        assertEquals("override the method", test5.test1());
        assertEquals("override the method", test5.test2());
        assertEquals("override the method", test5.test3());
    }

For more details, please read org.springframework.core.annotation.alisfors.AlisforsTests.

Comment From: pivotal-issuemaster

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Comment From: pivotal-issuemaster

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Comment From: sbrannen

Related to #18852

Comment From: sbrannen

Please note that we would not introduce this new feature in 4.3.x. Rather, if the team decides to introduce this, it would most likely be for 5.3.x or later.

In any case, please do not re-implement the feature against master until the team has decided in favor of the feature.

Comment From: loongs-zhang

Thank you for your valuable suggestions. I will re-support the sub-features in the 5.3.x branch, so please re-examine them at that time

Comment From: sbrannen

In https://github.com/spring-projects/spring-framework/pull/25592#issuecomment-674548229, I asked that you:

not re-implement the feature against master until the team has decided in favor of the feature.

However, since you disregarded that and submitted #25857 anyway, I am closing this as a duplicate.

Comment From: loongs-zhang

I'm very sorry to misunderstood your idea. I thought you asked me to redevelop this feature based on the latest code.

------------------ 原始邮件 ------------------ 发件人: "spring-projects/spring-framework" <notifications@github.com>; 发送时间: 2020年11月2日(星期一) 下午5:41 收件人: "spring-projects/spring-framework"<spring-framework@noreply.github.com>; 抄送: "炼龙"<1936978077@qq.com>;"Mention"<mention@noreply.github.com>; 主题: Re: [spring-projects/spring-framework] Support multiple aliases via @AliasFor (#25592)

In #25592 (comment), I asked that you:

not re-implement the feature against master until the team has decided in favor of the feature.

However, since you disregarded that and submitted #25857 anyway, I am closing this as a duplicate.

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