Java 注解@AliasFor使用方式及实际案例

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AliasFor {
    String value() default "";
    Class<? extends Annotation> annotation() default Annotation.class;
    String attribute() default "";
}

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyMapping {
    @AliasFor("path")
    String value() default "";
    @AliasFor("value")
    String path() default "";
}

@MyMapping("/hello")
public void sayHello() {}
// 或者
@MyMapping(path = "/hello")
public void sayHello() {}

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Component
public @interface MyService {
    @AliasFor(annotation = Component.class, attribute = "value")
    String name() default "";
}

@MyService("myBean")
public class MyBean {}

private static Map<String, List<String>> resolveAliasMappings(Class<? extends Annotation> annotationType) {
    Map<String, List<String>> aliasMap = new HashMap<>();
    for (Method attribute : annotationType.getDeclaredMethods()) {
        AliasFor aliasFor = attribute.getAnnotation(AliasFor.class);
        if (aliasFor != null) {
            String aliasName = aliasFor.value();
            aliasMap.computeIfAbsent(attribute.getName(), k -> new ArrayList<>()).add(aliasName);
        }
    }
    return aliasMap;
}

@AliasFor("value")
String path() default "/default"; // 不一致将抛出异常

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@PreAuthorize("hasRole('ADMIN')")
public @interface AdminOnly {
    @AliasFor(annotation = PreAuthorize.class, attribute = "value")
    String value() default "hasRole('ADMIN')";
}

@RestController
public class UserController {
    @AdminOnly
    public String getAdminData() {
        return "only for admin";
    }
    @AdminOnly("hasRole('MANAGER')")
    public String getManagerData() {
        return "only for manager";
    }
}