Spring自定义注释：如何继承属性？

Question

我正在创建自己的自定义快捷方式注释，如Spring Documentation中所述 ：

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Transactional(value = "Custom", readOnly = true)
public @interface CustomTransactional {
}

是否有可能，通过我的自定义注释，我还可以设置@Transactional中可用的任何其他属性？ 我想能够使用我的注释，例如，像这样：

@CustomTransactional(propagation = Propagation.REQUIRED)
public class MyClass {

}

Answer 1

不，如果您想要以这种方式在自定义注释本身上设置其他属性，那将无效：

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Transactional(value = "Custom", readOnly = true, propagation = Propagation.REQUIRED)
public @interface CustomTransactional {
}

一个解决方案（坏的:-)）可以用您在场景中看到的基本案例集来定义多个注释：

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Transactional(value = "Custom", readOnly = true, propagation = Propagation.REQUIRED)
public @interface CustomTransactionalWithRequired {
}

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Transactional(value = "Custom", readOnly = true, propagation = Propagation.SUPPORTED)
public @interface CustomTransactionalWithSupported {
}

Answer 2

在（至少）Spring 4中，您可以通过指定注释中的元素来完成此操作，例如：

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Transactional(value = "Custom", readOnly = true)
public @interface CustomTransactional {
    Propagation propagation() default Propagation.SUPPORTED;
}

资料来源： http ： //docs.spring.io/spring/docs/current/spring-framework-reference/html/beans.html#beans-meta-annotations