SpringBoot中注解@AliasFor的使用详解 SpringBoot中注解@AliasFor的使用详

简介
用法1：注解的属性互为别名

简介
实例

用法2.继承父注解的属性，不重写属性名

简介
代码

用法3：继承父注解的属性，并重写属性名

简介
代码

简介本文用示例介绍@AliasFor（别名）注解的用法。

用法1：注解的属性互为别名

简介
【SpringBoot中注解@AliasFor的使用详解】它可以注解到自定义注解的两个属性上，表示这两个互为别名，也就是说这两个属性其实同一个含义。

其中一个属性名必须是"value"
无论指明设置哪个属性名设置属性值，另一个属性名也是同样属性值，也可以缺省属性名。
若两个都指明属性值，要求值必须相同，否则会报错。
使用简洁。这样使用之后，@MyAnno(location="shanghai")可以直接写为：@MyAnno("shanghai");

这个功能产生的原因：
若自定义注解有一个属性，且该属性命名上为了体现其含义，调用方必须每次使用自定义注解的时候，都必须写明属性，然后设置，这样稍微麻烦。

实例
注解

package com.example.annotation; import org.springframework.core.annotation.AliasFor; import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})@Documented@Inheritedpublic @interface MyAnnotation {@AliasFor(attribute = "location")String value() default ""; @AliasFor(attribute = "value")String location() default ""; }

控制器

package com.example.controller; import com.example.annotation.MyAnnotation; import org.springframework.core.annotation.AnnotationUtils; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController@RequestMapping("/hello")public class HelloController { @MyAnnotation(value = "https://www.it610.com/article/location")/*//下边这两种写法结果与上边是相同的@MyAnnotation("location")@MyAnnotation(location = "location")*/@RequestMapping("/test1")public String test1() {MyAnnotation myAnnotation = null; try {myAnnotation = AnnotationUtils.getAnnotation(this.getClass().getMethod("test1"), MyAnnotation.class); } catch (NoSuchMethodException e) {e.printStackTrace(); } return"value:" + myAnnotation.value() + "; loation:" + myAnnotation.location(); }}

测试
前端访问：http://localhost:8080/hello/test1
前端结果（value和location都是同一个值）

value:location; loation:location

用法2.继承父注解的属性，不重写属性名简介
子注解的属性值的读写，其实是对父注解的属性值的读写。（对继承的属性来说）
此时，只能读写继承了的属性值。

代码
注解

package com.example.annotation; import org.springframework.core.annotation.AliasFor; import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})@Documented@Inheritedpublic @interface MyAnnotation {@AliasFor(attribute = "location")String value() default ""; @AliasFor(attribute = "value")String location() default ""; }

package com.example.annotation; import org.springframework.core.annotation.AliasFor; import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})@Documented@Inherited@MyAnnotationpublic @interface SubMyAnnotation {@AliasFor(annotation = MyAnnotation.class)String location() default ""; //这个不能写，只能有一个与父属性名同名的属性，否则报错//@AliasFor(annotation = MyAnnotation.class)//String value() default ""; }

控制器

package com.example.controller; import com.example.annotation.MyAnnotation; import com.example.annotation.SubMyAnnotation; import org.springframework.core.annotation.AnnotatedElementUtils; import org.springframework.core.annotation.AnnotationUtils; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController@RequestMapping("/hello")public class HelloController {@SubMyAnnotation(location = "location(my)")@RequestMapping("/test")public String test() {SubMyAnnotation subMyAnnotation = null; MyAnnotation myAnnotation = null; MyAnnotation myAnnotation1 = null; try {subMyAnnotation = AnnotationUtils.getAnnotation(this.getClass().getMethod("test"), SubMyAnnotation.class); myAnnotation = AnnotationUtils.getAnnotation(this.getClass().getMethod("test"), MyAnnotation.class); myAnnotation1 = AnnotatedElementUtils.getMergedAnnotation(this.getClass().getMethod("test"), MyAnnotation.class); } catch (NoSuchMethodException e) {e.printStackTrace(); } return "loation(sub):" + subMyAnnotation.location() + "\n" +"location:" + myAnnotation.location() + "\n" +"location:" + myAnnotation1.location(); }}

测试
前端访问：http://localhost:8080/hello/test
结果

loation(sub):location(my)
location:
location:location(my)

用法3：继承父注解的属性，并重写属性名简介
子注解的属性值的读写，其实是对父注解的属性值的读写。（对重写的属性来说）
无论指明设置哪个属性名设置属性值，另一个属性名也是同样属性值，不可以缺省属性名。
若两个都指明属性值，要求值必须相同，否则会报错。
代码
注解

package com.example.annotation; import org.springframework.core.annotation.AliasFor; import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})@Documented@Inheritedpublic @interface MyAnnotation {@AliasFor(attribute = "location")String value() default ""; @AliasFor(attribute = "value")String location() default ""; }

package com.example.annotation; import org.springframework.core.annotation.AliasFor; import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME)@Target({ElementType.METHOD, ElementType.TYPE})@Documented@Inherited@MyAnnotationpublic @interface SubMyAnnotation {@AliasFor(attribute = "value", annotation = MyAnnotation.class)String subValue() default ""; @AliasFor(attribute = "location", annotation = MyAnnotation.class)String subLocation() default ""; //subLocation属性写成下边这两种结果是一样的//@AliasFor(attribute = "value", annotation = MyAnnotation.class)//String subLocation() default ""; //@AliasFor(value = "https://www.it610.com/article/location", annotation = MyAnnotation.class)//String subLocation() default ""; //}

控制器

package com.example.controller; import com.example.annotation.MyAnnotation; import com.example.annotation.SubMyAnnotation; import org.springframework.core.annotation.AnnotatedElementUtils; import org.springframework.core.annotation.AnnotationUtils; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController@RequestMapping("/hello")public class HelloController {@SubMyAnnotation(subValue = "https://www.it610.com/article/subLocation")//@SubMyAnnotation(subLocation = "subLocation")//这个与上边结果相同//@SubMyAnnotation("subLocation")//缺省属性名会报错@RequestMapping("/test")public String test() {SubMyAnnotation subMyAnnotation = null; MyAnnotation myAnnotation = null; MyAnnotation myAnnotation1 = null; try {subMyAnnotation = AnnotationUtils.getAnnotation(this.getClass().getMethod("test"), SubMyAnnotation.class); myAnnotation = AnnotationUtils.getAnnotation(this.getClass().getMethod("test"), MyAnnotation.class); myAnnotation1 = AnnotatedElementUtils.getMergedAnnotation(this.getClass().getMethod("test"), MyAnnotation.class); } catch (NoSuchMethodException e) {e.printStackTrace(); }return "subValue:" + subMyAnnotation.subValue() + "; subLoation:" + subMyAnnotation.subLocation() + "\n" +"value:" + myAnnotation.value() + "; location:" + myAnnotation.location() + "\n" +"value:" + myAnnotation1.value() + "; location:" + myAnnotation1.location(); }}

测试
前端访问：http://localhost:8080/hello/test
结果