Spring 5 中文解析核心篇-IoC容器之AOP编程(上)

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"面向切面的编程（AOP）通过提供另一种思考程序结构的方式来补充面向对像的编程（OOP）。OOP中模块化的关键单元是类，而在AOP中模块化是切面。切面使关注点（例如事务管理）的模块化可以跨越多种类型和对象。(这种关注在AOP文献中通常被称为“跨领域”关注。)"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring的关键组件之一是AOP框架。虽然Spring IoC容器不依赖于AOP(这意味着如果你不想使用AOP，就不需要使用AOP)，但AOP对Spring IoC进行了补充，提供了一个非常强大的中间件解决方案。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"​  "},{"type":"text","marks":[{"type":"strong"}],"text":"具有AspectJ切入点的Spring AOP"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring提供了使用"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-schema","title":null},"content":[{"type":"text","text":"基于schema"}]},{"type":"text","text":"的方法或"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-ataspectj","title":null},"content":[{"type":"text","text":"@AspectJ注解"}]},{"type":"text","text":"样式来编写自定义切面的简单而强大的方法。这两种样式都提供了完全类型化的建议，并使用了AspectJ切入点语言，同时仍然使用Spring AOP进行编织。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本章讨论基于"},{"type":"codeinline","content":[{"type":"text","text":"schema"}]},{"type":"text","text":"和基于"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"的AOP支持。"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-api","title":null},"content":[{"type":"text","text":"下一章"}]},{"type":"text","text":"将讨论较低级别的AOP支持。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"AOP在Spring框架中用于："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"提供声明式企业服务。此类服务中最重要的是"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/data-access.html#transaction-declarative","title":null},"content":[{"type":"text","text":"声明式事务管理"}]},{"type":"text","text":"。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"让用户实现自定义切面，并用AOP补充其对OOP的使用。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果你只对通用声明性服务或其他预包装的声明性中间件服务（例如池）感兴趣，则无需直接使用Spring AOP，并且可以跳过本章的大部分内容。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":5},"content":[{"type":"text","text":"5.1 AOP概念"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"让我们首先定义一些主要的AOP概念和术语。这些术语不是特定于Spring的。不幸的是，AOP术语并不是特别直观。但是，如果使用Spring自己的术语，将会更加令人困惑。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"切面：涉及多个类别的关注点的模块化。事务管理是企业Java应用程序中横切关注的一个很好的例子。在Spring AOP中，切面是通过使用常规类（"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-schema","title":null},"content":[{"type":"text","text":"基于schema"}]},{"type":"text","text":"的方法）或使用"},{"type":"codeinline","content":[{"type":"text","text":"@Aspect"}]},{"type":"text","text":"注解（"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-ataspectj","title":null},"content":[{"type":"text","text":"@AspectJ样式"}]},{"type":"text","text":"）注释的常规类来实现的。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"连接点：程序执行过程中的一点，例如方法的执行或异常的处理。在Spring AOP中，连接点始终代表方法的执行。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通知：切面在特定的连接点处采取的操作。不同类型的通知包括：“"},{"type":"codeinline","content":[{"type":"text","text":"around"}]},{"type":"text","text":"”，“"},{"type":"codeinline","content":[{"type":"text","text":"before"}]},{"type":"text","text":"”和“"},{"type":"codeinline","content":[{"type":"text","text":"after"}]},{"type":"text","text":"”通知。（通知类型将在后面讨论。）包括Spring在内的许多AOP框架都将通知建模为拦截器，并在连接点周围维护一系列拦截器。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"切入点：表示匹配连接点。通知与切入点表达式关联，并在与该切入点匹配的任何连接点处运行（例如，执行具有特定名称的方法）。切入点表达式匹配的连接点的概念是AOP的核心，默认情况下，Spring使用"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"切入点表达语言。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"引入：在类型上声明其他方法或字段。Spring AOP允许你向任何通知对象引入新的接口（和相应的实现）。例如，你可以使用引入使Bean实现IsModified接口，以简化缓存。（引入在"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"社区中称为类型间声明。）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"目标对象：一个或多个切面通知的对象。也称为“通知对象”。由于Spring AOP是使用运行时代理实现的，因此该对象始终是代理对象。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"AOP代理：由AOP框架创建的对象，用于实现切面约定（通知方法执行等）。在Spring Framework中，AOP代理是"},{"type":"codeinline","content":[{"type":"text","text":"JDK"}]},{"type":"text","text":"动态代理或"},{"type":"codeinline","content":[{"type":"text","text":"CGLIB"}]},{"type":"text","text":"代理。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"编织：将切面与其他应用程序类型或对象链接以创建通知的对象。这可以在编译时（例如，使用"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编译器），加载时或在运行时完成。像其他纯Java AOP框架一样，Spring AOP在运行时执行编织。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP包括以下类型的通知："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前置通知：在连接点之前运行但无法阻止执行流前进到连接点的通知（除非它引发异常）。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"后置通知：连接点正常完成后要运行的通知（例如，如果某个方法返回而没有引发异常）。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"后置异常通知：如果方法因抛出异常而退出，将执行的通知。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最终通知：无论连接点退出的方式如何（正常或异常返回），都将执行通知。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"环绕通知：围绕连接点的通知，例如方法调用。这是最强大的通知。环绕通知可以在方法调用之前和之后执行自定义行为。它还负责选择是继续到连接点，还是通过返回自己的返回值或抛出异常来简化通知的方法执行。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"环绕通知是最通用的通知。由于Spring AOP与"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"一样，提供了各种通知类型，因此我们建议你使用功能最弱的建议类型，以实现所需的行为。例如，如果你只需要使用方法的返回值更新缓存，则最好使用后置通知而不是环绕通知，尽管环绕通知可以完成相同的事情。使用最具体的通知类型可提供更简单的编程模型，并减少出错的可能性。例如，你不需要在用于环绕通知的"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}]},{"type":"text","text":"上调用"},{"type":"codeinline","content":[{"type":"text","text":"proceed()"}]},{"type":"text","text":"方法，因此，你不会失败。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所有通知参数都是静态类型的，因此你可以使用适当类型（例如，从方法执行返回的值的类型）而不是对象数组的 通知参数。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"切入点匹配的连接点的概念是AOP的关键，它与仅提供拦截功能的旧技术不同。切入点使通知的目标独立于面向对象的层次结构。例如，你可以将提供声明性事务管理的环绕通知应用于跨越多个对象（例在服务层中的所有业务操作）的一组方法。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":5},"content":[{"type":"text","text":"5.2 AOP能力和目标"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP是用纯Java实现的。不需要特殊的编译过程。Spring AOP不需要控制类加载器的层次结构，因此适合在Servlet容器或应用程序服务器中使用。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP当前仅支持方法执行连接点（通知在Spring Bean上执行方法）。尽管可以在不破坏核心Spring AOP API的情况下添加对字段拦截的支持，但并未实现字段拦截。如果需要通知字段访问和更新连接点，请考虑使用诸如"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"之类的语言。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP的AOP方法不同于大多数其他AOP框架。目的不是提供最完整的AOP实现（尽管Spring AOP相当强大）。相反，其目的是在AOP实现和Spring IoC之间提供紧密的集成，以帮助解决企业应用程序中的常见问题。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"因此，例如，通常将Spring Framework的AOP功能与Spring IoC容器结合使用。通过使用常规bean定义语法来配置切面（尽管这允许强大的“自动代理”功能）。这是与其他AOP实现的关键区别。使用Spring AOP不能轻松或有效地完成一些事情，比如通知非常细粒度的对象(通常是域对象)。在这种情况下，"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"是最佳选择。但是，我们的经验是，Spring AOP为AOP可以解决的企业Java应用程序中的大多数问题提供了出色的解决方案。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP从未努力与"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"竞争以提供全面的AOP解决方案。我们认为，基于代理的框架（如Spring AOP）和成熟的框架（如"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"）都是有价值的，它们是互补的，而不是竞争。Spring无缝地将Spring AOP和IoC与"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"集成在一起，以在基于Spring的一致应用程序架构中支持AOP的所有功能。这种集成不会影响Spring AOP API或AOP "},{"type":"codeinline","content":[{"type":"text","text":"Alliance"}]},{"type":"text","text":"API。Spring AOP仍然向后兼容。请参阅"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-api","title":null},"content":[{"type":"text","text":"下一章"}]},{"type":"text","text":"，以讨论Spring AOP API。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring框架的中心宗旨之一是非侵入性。这就是不应该强迫你将特定于框架的类和接口引入你的业务或领域模型的思想。但是，在某些地方，Spring Framework确实为你提供了将特定于Spring Framework的依赖项引入代码库的选项。提供此类选项的理由是，在某些情况下，以这种方式阅读或编码某些特定功能可能会变得更加容易。但是，Spring框架（几乎）总是为你提供选择：你可以自由地就哪个选项最适合你的特定用例或场景做出明智的决定。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"与本章相关的一种选择是选择哪种AOP框架（以及哪种AOP样式）。你可以选择"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"和或Spring AOP。你也可以选择"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"注解样式方法或Spring XML配置样式方法。本章选择首先介绍"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"风格的方法，这不能表明Spring比Spring XML配置风格更喜欢"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"注释风格的方法(备注：使用"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编写例子不能说明Spring更喜欢"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"注解编程)。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有关每种样式的“来龙去脉”的更完整讨论，请参见"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-choosing","title":null},"content":[{"type":"text","text":"选择要使用的AOP声明样式"}]},{"type":"text","text":"。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":5},"content":[{"type":"text","text":"5.3 AOP代理"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP默认将标准JDK动态代理用于AOP代理。这使得可以代理任何接口（或一组接口）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP也可以使用CGLIB代理。这对于代理类而不是接口是必需的。默认情况下，如果业务对象未实现接口，则使用CGLIB。由于对接口而不是对类进行编程是一种好习惯，因此业务类通常实现一个或多个业务接口。在某些情况下（可能极少发生），你需要通知在接口上未声明的方法，或需要将代理对象作为具体类型传递给方法，则可以"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-proxying","title":null},"content":[{"type":"text","text":"强制使用CGLIB"}]},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"掌握Spring AOP是基于代理的这一事实很重要。请参阅"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-understanding-aop-proxies","title":null},"content":[{"type":"text","text":"了解AOP代理"}]},{"type":"text","text":"以全面了解此实现细节的实际含义。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":5},"content":[{"type":"text","text":"5.4 @AspectJ支持"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"是一种将切面声明为带有注解的常规Java类的样式。"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"样式是"},{"type":"link","attrs":{"href":"https://www.eclipse.org/aspectj","title":null},"content":[{"type":"text","text":"AspectJ项目"}]},{"type":"text","text":"在AspectJ 5版本中引入的。Spring使用"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"提供的用于切入点解析和匹配的库来解释与AspectJ 5相同的注解。但是，AOP运行时仍然是纯Spring AOP，并且不依赖于"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编译器或编织器。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编译器和编织器可以使用完整的"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"语言，有关"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-using-aspectj","title":null},"content":[{"type":"text","text":"在Spring Applications中使用AspectJ"}]},{"type":"text","text":"进行了讨论。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.1 激活"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}],"marks":[{"type":"strong"}]},{"type":"text","marks":[{"type":"strong"}],"text":"支持"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"要在Spring配置中使用"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"切面，你需要启用Spring支持以基于"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"切面配置Spring 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AOP。接下来的两个示例显示了一个不太有用的切面所需的最小定义。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"两个示例中的第一个示例显示了应用程序上下文中的常规bean定义，该定义指向具有"},{"type":"codeinline","content":[{"type":"text","text":"@Aspect"}]},{"type":"text","text":"注解的bean类："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"html"},"content":[{"type":"text","text":"\n \n\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这两个示例中的第二个示例显示了"},{"type":"codeinline","content":[{"type":"text","text":"NotVeryUsefulAspect"}]},{"type":"text","text":"类定义，该类定义使用"},{"type":"codeinline","content":[{"type":"text","text":"org.aspectj.lang.annotation.Aspect"}]},{"type":"text","text":"注解进行注释；"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"package org.xyz;\nimport org.aspectj.lang.annotation.Aspect;\n\n@Aspect\npublic class NotVeryUsefulAspect 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AOP中，切面本身不能成为其他切面的通知目标。类上的"},{"type":"codeinline","content":[{"type":"text","text":"@Aspect"}]},{"type":"text","text":"注解将其标记为一个切面，因此将其从自动代理中排除。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.3 声明切入点"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"切入点确定了感兴趣的连接点，从而使我们能够控制何时执行通知。Spring AOP仅支持Spring Bean的方法执行连接点，因此你可以将切入点视为与Spring Bean上的方法执行匹配。切入点声明由两部分组成：一个包含名称和任何参数的签名，以及一个切入点表达式，该表达式精确确定我们感兴趣的方法执行。在AOP的"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"注解样式中，常规方法定义提供了切入点签名，并且使用"},{"type":"codeinline","content":[{"type":"text","text":"@Pointcut"}]},{"type":"text","text":"注解指示了切入点表达式（用作切入点签名的方法必须具有"},{"type":"codeinline","content":[{"type":"text","text":"void"}]},{"type":"text","text":"返回类型）。一个示例可能有助于使切入点签名和切入点表达式之间的区别变得清晰。下面的示例定义一个名为"},{"type":"codeinline","content":[{"type":"text","text":"anyOldTransfer"}]},{"type":"text","text":"的切入点，该切入点与任何名为"},{"type":"codeinline","content":[{"type":"text","text":"transfer"}]},{"type":"text","text":"方法的执行相匹配："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Pointcut(\"execution(* transfer(..))\") // 切入点表达式\nprivate void anyOldTransfer() {} // 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）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"支持的切入点指示符"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP支持以下在切入点表达式中使用的"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"切入点指示符（PCD）："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"execution"}]},{"type":"text","text":": 用于匹配方法执行的连接点。这是使用Spring 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AOP解释的切入点表达式中使用这些切入点指示符会导致抛出"},{"type":"codeinline","content":[{"type":"text","text":"IllegalArgumentException"}]},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP支持的切入点指示符集合可能会在将来的版本中扩展，以支持更多的 "},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"切入点指示符。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"由于Spring AOP仅将匹配限制为仅方法执行连接点，因此前面对切入点指示符的讨论所给出的定义比在"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编程指南中所能找到的要窄。此外，"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"本身具有基于类型的语义，并且在执行连接点处，"},{"type":"codeinline","content":[{"type":"text","text":"this"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"target"}]},{"type":"text","text":"都引用同一个对象：执行该方法的对象。Spring AOP是基于代理的系统，可区分代理对象本身（绑定到此对象）和代理背后的目标对象（绑定到目标）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"由于Spring的AOP框架基于代理的性质，因此根据定义，不会拦截目标对象内的调用。对于JDK代理，只能拦截代理上的公共接口方法调用。使用CGLIB，将拦截代理上的公共方法和受保护的方法调用（必要时甚至包可见的方法）。但是，通常应通过公共签名设计通过代理进行的常见交互。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"请注意，切入点定义通常与任何拦截方法匹配。如果严格地将切入点设置为仅公开使用，即使在CGLIB代理方案中通过代理可能存在非公开交互，也需要相应地进行定义。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果你的拦截需要在目标类中包括方法调用甚至构造函数，请考虑使用Spring驱动的"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.7.RELEASE/spring-framework-reference/core.html#aop-aj-ltw","title":null},"content":[{"type":"text","text":"本地AspectJ编织"}]},{"type":"text","text":"，而不是Spring的基于代理的AOP框架。这构成了具有不同特征的AOP使用模式，因此在做出决定之前一定要熟悉编织。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP还支持其他名为bean的PCD。使用PCD，可以将连接点的匹配限制为特定的命名Spring Bean或一组命名Spring Bean（使用通配符时）。Bean PCD具有以下形式："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"bean(idOrNameOfBean)\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"idOrNameOfBean"}]},{"type":"text","text":"标记可以是任何Spring bean的名称。提供了使用"},{"type":"codeinline","content":[{"type":"text","text":"*"}]},{"type":"text","text":"字符的有限通配符支持，因此，如果为Spring bean建立了一些命名约定，则可以编写bean PCD表达式来选择它们。与其他切入点指示符一样，bean PCD可以与"},{"type":"codeinline","content":[{"type":"text","text":"&&"}]},{"type":"text","text":"(和)、"},{"type":"codeinline","content":[{"type":"text","text":"||"}]},{"type":"text","text":"(或)、和"},{"type":"codeinline","content":[{"type":"text","text":"!"}]},{"type":"text","text":"(否定)运算符一起使用。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Bean PCD仅在Spring AOP中受支持，而在本地"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编织中不受支持。它是"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"定义的标准PCD的特定于Spring的扩展，因此不适用于"},{"type":"codeinline","content":[{"type":"text","text":"@Aspect"}]},{"type":"text","text":"模型中声明的切面。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Bean PCD在实例级别（基于Spring bean名称概念构建）上运行，而不是仅在类型级别（基于编织的AOP受其限制）上运行。基于实例的切入点指示符是Spring基于代理的AOP框架的特殊功能，并且与Spring bean工厂紧密集成，因此可以自然而直接地通过名称识别特定bean。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"组合切入点表达式"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"&&"}]},{"type":"text","text":"、"},{"type":"codeinline","content":[{"type":"text","text":"||"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"!"}]},{"type":"text","text":"组合切入点表达式。你还可以按名称引用切入点表达式。以下示例显示了三个切入点表达式："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Pointcut(\"execution(public * *(..))\")\nprivate void anyPublicOperation() {} //1\n\n@Pointcut(\"within(com.xyz.someapp.trading..*)\")\nprivate void inTrading() {} //2\n\n@Pointcut(\"anyPublicOperation() && inTrading()\")\nprivate void tradingOperation() {} //3\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"numberedlist","attrs":{"start":null,"normalizeStart":1},"content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","text":"如果方法执行连接点表示任何公共方法的执行，则"},{"type":"codeinline","content":[{"type":"text","text":"anyPublicOperation"}]},{"type":"text","text":"匹配。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","text":"如果交易模块中有方法执行，则"},{"type":"codeinline","content":[{"type":"text","text":"inTrading"}]},{"type":"text","text":"匹配。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":3,"align":null,"origin":null},"content":[{"type":"text","text":"如果方法执行代表交易模块中的任何公共方法，则"},{"type":"codeinline","content":[{"type":"text","text":"tradingOperation"}]},{"type":"text","text":"匹配。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最佳实践是从较小的命名组件中构建更复杂的切入点表达式，如先前所示。按名称引用切入点时，将应用常规的Java可见性规则（你可以看到相同类型的private切入点，层次结构中"},{"type":"codeinline","content":[{"type":"text","text":"protected"}]},{"type":"text","text":"的切入点，任何位置的public切入点，等等）。可见性不影响切入点匹配。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"共享通用切入点定义"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在企业级应用中，开发人员通常希望从多个方面引用应用程序的模块和特定的操作集。我们建议为此定义一个"},{"type":"codeinline","content":[{"type":"text","text":"SystemArchitecture"}]},{"type":"text","text":"切面，以捕获常见的切入点表达式意图。这样的切面通常类似于以下示例："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"package com.xyz.someapp;\n\nimport org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.Pointcut;\n\n@Aspect\npublic class SystemArchitecture {\n\n /**\n * A join point is in the web layer if the method is defined\n * in a type in the com.xyz.someapp.web package or any sub-package\n * under that.\n */\n @Pointcut(\"within(com.xyz.someapp.web..*)\")\n public void inWebLayer() {}\n\n /**\n * A join point is in the service layer if the method is defined\n * in a type in the com.xyz.someapp.service package or any sub-package\n * under that.\n */\n @Pointcut(\"within(com.xyz.someapp.service..*)\")\n public void inServiceLayer() {}\n\n /**\n * A join point is in the data access layer if the method is defined\n * in a type in the com.xyz.someapp.dao package or any sub-package\n * under that.\n */\n @Pointcut(\"within(com.xyz.someapp.dao..*)\")\n public void inDataAccessLayer() {}\n\n /**\n * A business service is the execution of any method defined on a service\n * interface. This definition assumes that interfaces are placed in the\n * \"service\" package, and that implementation types are in sub-packages.\n *\n * If you group service interfaces by functional area (for example,\n * in packages com.xyz.someapp.abc.service and com.xyz.someapp.def.service) then\n * the pointcut expression \"execution(* com.xyz.someapp..service.*.*(..))\"\n * could be used instead.\n *\n * Alternatively, you can write the expression using the 'bean'\n * PCD, like so \"bean(*Service)\". (This assumes that you have\n * named your Spring service beans in a consistent fashion.)\n */\n @Pointcut(\"execution(* com.xyz.someapp..service.*.*(..))\")\n public void businessService() {}\n\n /**\n * A data access operation is the execution of any method defined on a\n * dao interface. This definition assumes that interfaces are placed in the\n * \"dao\" package, and that implementation types are in sub-packages.\n */\n @Pointcut(\"execution(* com.xyz.someapp.dao.*.*(..))\")\n public void dataAccessOperation() {}\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以在需要切入点表达式的任何地方引用在此切面定义的切入点。例如，要使服务层具有事务性，你可以编写以下内容："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"html"},"content":[{"type":"text","text":"\n \n\n\n\n \n \n \n\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-schema","title":null},"content":[{"type":"text","text":"基于schema的AOP支持"}]},{"type":"text","text":"中讨论了"},{"type":"codeinline","content":[{"type":"text","text":""}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":""}]},{"type":"text","text":"元素。"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/data-access.html#transaction","title":null},"content":[{"type":"text","text":"事务管理"}]},{"type":"text","text":"中讨论了事务元素。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"实例"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP用户可能最常使用"},{"type":"codeinline","content":[{"type":"text","text":"execution"}]},{"type":"text","text":"切入点指示符。执行表达式的格式如下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"execution(modifiers-pattern? ret-type-pattern declaring-type-pattern?name-pattern(param-pattern)\n throws-pattern?)\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"除了返回类型模式（前面的代码片段中的"},{"type":"codeinline","content":[{"type":"text","text":"ret-type-pattern"}]},{"type":"text","text":"），名称模式("},{"type":"codeinline","content":[{"type":"text","text":"name-pattern"}]},{"type":"text","text":")和参数模式("},{"type":"codeinline","content":[{"type":"text","text":"param-pattern"}]},{"type":"text","text":")以外的所有部分都是可选的。返回类型模式确定要匹配连接点、方法的返回类型必须是什么。"},{"type":"text","marks":[{"type":"italic"}],"text":"最常用作返回类型模式。它匹配任何返回类型。仅当方法返回给定类型时，标准类型名称才匹配。名称模式与方法名称匹配。你可以将"},{"type":"text","text":"通配"},{"type":"codeinline","content":[{"type":"text","text":"*"}]},{"type":"text","text":"符用作名称模式的全部或一部分。如果你指定了声明类型模式，请在其后加上"},{"type":"codeinline","content":[{"type":"text","text":"."}]},{"type":"text","text":"将其加入名称模式组件。参数模式稍微复杂一些："},{"type":"codeinline","content":[{"type":"text","text":"()"}]},{"type":"text","text":"匹配不带参数的方法，而"},{"type":"codeinline","content":[{"type":"text","text":"(..)"}]},{"type":"text","text":"匹配任意数量（零个或多个）的参数。"},{"type":"codeinline","content":[{"type":"text","text":"(*)"}]},{"type":"text","text":"模式与采用任何类型的一个参数的方法匹配。"},{"type":"codeinline","content":[{"type":"text","text":"(*，String)"}]},{"type":"text","text":"与采用两个参数的方法匹配。第一个可以是任何类型，而第二个必须是字符串。有关更多信息，请查阅AspectJ编程指南的“"},{"type":"link","attrs":{"href":"https://www.eclipse.org/aspectj/doc/released/progguide/semantics-pointcuts.html","title":null},"content":[{"type":"text","text":"语言语义"}]},{"type":"text","text":"”部分。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以下示例显示了一些常用的切入点表达式："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"任何公共方法的执行："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"名称以"},{"type":"codeinline","content":[{"type":"text","text":"set"}]},{"type":"text","text":"开头的任何方法的执行："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"AccountService"}]},{"type":"text","text":"接口定义的任何方法的执行："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"service"}]},{"type":"text","text":"包中定义的任何方法的执行："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"service"}]},{"type":"text","text":"包或其子包之一中定义的任何方法的执行："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"service"}]},{"type":"text","text":"包中的任何连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"service"}]},{"type":"text","text":"包或其子包之一中的任何连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"代理实现"},{"type":"codeinline","content":[{"type":"text","text":"AccountService"}]},{"type":"text","text":"接口的任何连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"目标对象实现"},{"type":"codeinline","content":[{"type":"text","text":"AccountService"}]},{"type":"text","text":"接口的任何连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"任何采用单个参数并且在运行时传递的参数为"},{"type":"codeinline","content":[{"type":"text","text":"Serializable"}]},{"type":"text","text":"的连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"目标对象具有"},{"type":"codeinline","content":[{"type":"text","text":"@Transactional"}]},{"type":"text","text":"注解的任何连接点（仅在Spring AOP中方法执行）："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你也可以在绑定形式中使用"},{"type":"codeinline","content":[{"type":"text","text":"@target"}]},{"type":"text","text":"。有关如何使注解对象在建议正文中可用的信息，请参见“"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-advice","title":null},"content":[{"type":"text","text":"声明通知"}]},{"type":"text","text":"”部分。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"目标对象的声明类型具有"},{"type":"codeinline","content":[{"type":"text","text":"@Transactional"}]},{"type":"text","text":"注解的任何连接点（仅在Spring AOP中方法执行）："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你也可以在绑定形式中使用"},{"type":"codeinline","content":[{"type":"text","text":"@within"}]},{"type":"text","text":"。有关如何使注解对象在通知正文中可用的信息，请参见“"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-advice","title":null},"content":[{"type":"text","text":"声明通知"}]},{"type":"text","text":"”部分。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"任何执行方法带有"},{"type":"codeinline","content":[{"type":"text","text":"@Transactional"}]},{"type":"text","text":"注解的连接点（仅在Spring AOP中是方法执行）："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你也可以在绑定形式中使用"},{"type":"codeinline","content":[{"type":"text","text":"@annotation"}]},{"type":"text","text":"。有关如何使注解对象在通知正文中可用的信息，请参见“"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-advice","title":null},"content":[{"type":"text","text":"声明通知"}]},{"type":"text","text":"”部分。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"任何采用单个参数的连接点（仅在Spring AOP中是方法执行），并且传递的参数的运行时类型具有"},{"type":"codeinline","content":[{"type":"text","text":"@Classified"}]},{"type":"text","text":"注解："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你也可以在绑定形式中使用"},{"type":"codeinline","content":[{"type":"text","text":"@args"}]},{"type":"text","text":"。请参阅“"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-advice","title":null},"content":[{"type":"text","text":"声明通知"}]},{"type":"text","text":"”部分，如何使通知对象中的注解对象可用。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"名为"},{"type":"codeinline","content":[{"type":"text","text":"tradeService"}]},{"type":"text","text":"的Spring bean上的任何连接点（仅在Spring AOP中执行方法）："}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring Bean上具有与通配符表达式"},{"type":"codeinline","content":[{"type":"text","text":"* Service"}]},{"type":"text","text":"匹配的名称的任何连接点（仅在Spring AOP中才执行方法）："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"写一个好的连接点"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在编译期间，"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"处理切入点以优化匹配性能。检查代码并确定每个连接点是否（静态或动态）匹配给定的切入点是一个耗时的过程。（动态匹配意味着无法从静态分析中完全确定匹配，并且在代码中进行了测试以确定在运行代码时是否存在实际匹配）。首次遇到切入点声明时，"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"将其重写为匹配过程的最佳形式。这是什么意思？基本上，切入点以DNF（析取范式）重写，并且对切入点的组件进行排序，以便首先检查那些较便宜(消耗最小)的组件。这意味着你不必担心理解各种切入点指示符的性能，并且可以在切入点声明中以任何顺序提供它们。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但是，"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"只能使用所告诉的内容。为了获得最佳的匹配性能，你应该考虑他们试图达到的目标，并在定义中尽可能缩小匹配的搜索空间。现有的指示符自然分为三类之一：同类、作用域和上下文："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Kinded"}]},{"type":"text","text":"指示器选择特定类型的连接点:"},{"type":"codeinline","content":[{"type":"text","text":"execution"}]},{"type":"text","text":"、 "},{"type":"codeinline","content":[{"type":"text","text":"get"}]},{"type":"text","text":"、 "},{"type":"codeinline","content":[{"type":"text","text":"set"}]},{"type":"text","text":"、"},{"type":"codeinline","content":[{"type":"text","text":"call"}]},{"type":"text","text":"和 "},{"type":"codeinline","content":[{"type":"text","text":"handler"}]},{"type":"text","text":"。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Scoping"}]},{"type":"text","text":"指示器选择一组感兴趣的连接点(可能是多种类型的):"},{"type":"codeinline","content":[{"type":"text","text":"within"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"withincode"}]}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Contextual"}]},{"type":"text","text":"指示符根据上下文匹配(和可选绑定):"},{"type":"codeinline","content":[{"type":"text","text":"this"}]},{"type":"text","text":"、"},{"type":"codeinline","content":[{"type":"text","text":"target"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"@annotation"}]}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"编写正确的切入点至少应包括前两种类型（"},{"type":"codeinline","content":[{"type":"text","text":"Kinded"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"Scoping"}]},{"type":"text","text":"）。你可以包括上下文指示符以根据连接点上下文进行匹配，也可以绑定该上下文以在通知中使用。仅提供"},{"type":"codeinline","content":[{"type":"text","text":"Kinded"}]},{"type":"text","text":"的标识符或仅提供"},{"type":"codeinline","content":[{"type":"text","text":"Contextual"}]},{"type":"text","text":"的标识符是可行的，但是由于额外的处理和分析，可能会影响编织性能（使用的时间和内存）。"},{"type":"codeinline","content":[{"type":"text","text":"Scoping"}]},{"type":"text","text":"指定符的匹配非常快，使用它们意味着"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"可以非常迅速地消除不应进一步处理的连接点组。一个好的切入点应尽可能包括一个切入点。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"参考代码："},{"type":"codeinline","content":[{"type":"text","text":"com.liyong.ioccontainer.starter.AopIocContiner"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.4 声明通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通知与切入点表达式关联，并且在切入点匹配的方法执行之前、之后或周围运行。切入点表达式可以是对命名切入点的简单引用，也可以是在适当位置声明的切入点表达式。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"前置通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"@Before"}]},{"type":"text","text":"注解在一个切面中声明前置通知："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.Before;\n\n@Aspect\npublic class BeforeExample {\n\n @Before(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\")\n public void doAccessCheck() {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果使用就地切入点表达式，则可以将前面的示例重写为以下示例："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.Before;\n\n@Aspect\npublic class BeforeExample {\n\n @Before(\"execution(* com.xyz.myapp.dao.*.*(..))\")\n public void doAccessCheck() {\n // ...\n }\n\n}\n\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"返回通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在当匹配方法正常的执行返回时，返回通知运行。你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"@AfterReturning"}]},{"type":"text","text":"注解进行声明："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.AfterReturning;\n\n@Aspect\npublic class AfterReturningExample {\n\n @AfterReturning(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\")\n public void doAccessCheck() {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以在同一切面内拥有多个通知声明（以及其他成员）。在这些示例中，我们仅显示单个通知声明，以及其中每个通知的效果。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有时，你需要在通知正文中访问返回的实际值。你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"@AfterReturning"}]},{"type":"text","text":"的形式绑定返回值以获取该访问，如以下示例所示："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.AfterReturning;\n\n@Aspect\npublic class AfterReturningExample {\n\n @AfterReturning(\n pointcut=\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\",\n returning=\"retVal\")\n public void doAccessCheck(Object retVal) {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"返回属性中使用的名称必须与"},{"type":"codeinline","content":[{"type":"text","text":"advice"}]},{"type":"text","text":"方法中的参数名称相对应。当方法执行返回时，返回值将作为相应的参数值传递到通知方法。"},{"type":"codeinline","content":[{"type":"text","text":"returning"}]},{"type":"text","text":"也将匹配限制为仅返回指定类型值的方法执行（在这种情况下为Object，它匹配任何返回值）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"请注意，当使用返回后通知时，不可能返回完全不同的引用。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"异常后置通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在抛异常通知后，当匹配的方法执行通过抛出异常退出时运行。你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"@AfterThrowing"}]},{"type":"text","text":"注解进行声明，如以下示例所示："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.AfterThrowing;\n\n@Aspect\npublic class AfterThrowingExample {\n\n @AfterThrowing(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\")\n public void doRecoveryActions() {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通常，你希望通知仅在引发给定类型的异常时才运行，并且你通常还需要访问通知正文中的引发异常。你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"throwing"}]},{"type":"text","text":"属性来限制匹配（如果需要）（否则，请使用"},{"type":"codeinline","content":[{"type":"text","text":"Throwable"}]},{"type":"text","text":"作为异常类型），并将抛出的异常绑定到通知的参数。以下示例显示了如何执行此操作："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.AfterThrowing;\n\n@Aspect\npublic class AfterThrowingExample {\n\n @AfterThrowing(\n pointcut=\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\",\n throwing=\"ex\")\n public void doRecoveryActions(DataAccessException ex) {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"throwing"}]},{"type":"text","text":"属性中使用的名称必须与通知方法中的参数名称相对应。当通过抛出异常退出方法执行时，该异常将作为相应的参数值传递给通知的方法。"},{"type":"codeinline","content":[{"type":"text","text":"throwing"}]},{"type":"text","text":"还将匹配仅限制为抛出指定类型的异常（在这种情况下为"},{"type":"codeinline","content":[{"type":"text","text":"DataAccessException"}]},{"type":"text","text":"）的方法执行。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"最终通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当匹配的方法执行退出时，通知（最终）运行。通过使用"},{"type":"codeinline","content":[{"type":"text","text":"@After"}]},{"type":"text","text":"注解声明它。之后必须准备处理正常和异常返回条件的通知。它通常用于释放资源和类似目的。以下示例显示了最终通知的用法："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.After;\n\n@Aspect\npublic class AfterFinallyExample {\n\n @After(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation()\")\n public void doReleaseLock() {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"环绕通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"最后一种通知是环绕通知。环绕通知在匹配方法的执行过程中“环绕”运行。它有机会在方法执行之前和之后执行工作，并确定何时、如何执行，甚至是否真的执行方法。如果需要以线程安全的方式（例如，启动和停止计时器）在方法执行之前和之后共享状态，则通常使用环绕通知。始终使用能力最小的通知来满足你的要求（也就是说，在通知可以使前置通知时，请勿用环绕通知）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通过使用"},{"type":"codeinline","content":[{"type":"text","text":"@Around"}]},{"type":"text","text":"注解来声明环绕通知。通知方法的第一个参数必须是"},{"type":"codeinline","content":[{"type":"text","text":"ProceedingJoinPoint"}]},{"type":"text","text":"类型。在通知的正文中，在"},{"type":"codeinline","content":[{"type":"text","text":"ProceedingJoinPoint"}]},{"type":"text","text":"上调用"},{"type":"codeinline","content":[{"type":"text","text":"proceed()"}]},{"type":"text","text":"会使底层(真正的执行方法)方法执行。"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"方法也可以传入"},{"type":"codeinline","content":[{"type":"text","text":"Object []"}]},{"type":"text","text":"。数组中的值用作方法执行时的参数。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当用"},{"type":"codeinline","content":[{"type":"text","text":"Object []"}]},{"type":"text","text":"进行调用时，"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"的行为与"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编译器所编译的"},{"type":"codeinline","content":[{"type":"text","text":"around"}]},{"type":"text","text":" 通知的"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"为略有不同。对于使用传统"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"语言编写的环绕通知，传递给"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"的参数数量必须与传递给环绕通知的参数数量（而不是基础连接点采用的参数数量）相匹配，并且传递给给定的参数位置会取代该值绑定到的实体的连接点处的原始值（不要担心，如果这现在没有意义）。Spring采取的方法更简单，并且更适合其基于代理的，仅执行的语义。如果你编译为Spring编写的"},{"type":"codeinline","content":[{"type":"text","text":"@AspectJ"}]},{"type":"text","text":"切面，并在"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编译器和"},{"type":"codeinline","content":[{"type":"text","text":"weaver"}]},{"type":"text","text":"中使用参数进行处理，则只需要意识到这种区别。有一种方法可以在Spring AOP和"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"之间100％兼容，并且在下面有关"},{"type":"link","attrs":{"href":"https://docs.spring.io/spring/docs/5.2.6.RELEASE/spring-framework-reference/core.html#aop-ataspectj-advice-params","title":null},"content":[{"type":"text","text":"通知参数的部分"}]},{"type":"text","text":"中对此进行了讨论。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以下示例显示了如何使用环绕通知："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"import org.aspectj.lang.annotation.Aspect;\nimport org.aspectj.lang.annotation.Around;\nimport org.aspectj.lang.ProceedingJoinPoint;\n\n@Aspect\npublic class AroundExample {\n\n @Around(\"com.xyz.myapp.SystemArchitecture.businessService()\")\n public Object doBasicProfiling(ProceedingJoinPoint pjp) throws Throwable {\n // start stopwatch\n Object retVal = pjp.proceed();\n // stop stopwatch\n return retVal;\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"环绕通知返回的值是该方法的调用者看到的返回值。例如，如果一个简单的缓存切面有一个值，则它可以从缓存中返回一个值，如果没有，则调用"},{"type":"codeinline","content":[{"type":"text","text":"proceed()"}]},{"type":"text","text":"。请注意，在环绕通知的正文中，"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"可能被调用一次，多次或完全不被调用。所有这些都是合法的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"参考代码："},{"type":"codeinline","content":[{"type":"text","text":"com.liyong.ioccontainer.starter.AopIocContiner"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"通知参数"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring提供了完全类型化的通知，这意味着你可以在通知签名中声明所需的参数（如我们先前在返回和抛出示例中所看到的），而不是一直使用"},{"type":"codeinline","content":[{"type":"text","text":"Object []"}]},{"type":"text","text":"数组。我们将在本节的后面部分介绍如何使参数和其他上下文值可用于通知主体。首先，我们看一下如何编写通用通知，以了解该通知当前通知的方法。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"获取当前"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}],"marks":[{"type":"strong"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"任何通知方法都可以将"},{"type":"codeinline","content":[{"type":"text","text":"org.aspectj.lang.JoinPoint"}]},{"type":"text","text":"类型的参数声明为其第一个参数。请注意，环绕通知声明"},{"type":"codeinline","content":[{"type":"text","text":"ProceedingJoinPoint"}]},{"type":"text","text":"类型为第一个参数，该参数是"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}]},{"type":"text","text":"的子类。"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}]},{"type":"text","text":"接口提供了许多有用的方法："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"getArgs()"}]},{"type":"text","text":": 返回方法参数。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"getThis()"}]},{"type":"text","text":": 返回代理对象。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"getTarget()"}]},{"type":"text","text":": 返回目标对象。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"getSignature()"}]},{"type":"text","text":": 返回通知使用的方法的描述。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"toString()"}]},{"type":"text","text":": 打印有关所有通知方法的有用描述。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有关更多详细信息，请参见"},{"type":"link","attrs":{"href":"https://www.eclipse.org/aspectj/doc/released/runtime-api/org/aspectj/lang/JoinPoint.html","title":null},"content":[{"type":"text","text":"javadoc"}]},{"type":"text","text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"传递参数给通知"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我们已经看到了如何绑定返回的值或异常值（在返回之后和引发通知之后）。要使参数值可用于通知正文，可以使用"},{"type":"codeinline","content":[{"type":"text","text":"args"}]},{"type":"text","text":"的绑定形式。如果在"},{"type":"codeinline","content":[{"type":"text","text":"args"}]},{"type":"text","text":"表达式中使用参数名称代替类型名称，则在调用通知时会将相应参数的值作为参数值传递。一个例子应该使这一点更清楚。假设你要通知以"},{"type":"codeinline","content":[{"type":"text","text":"Account"}]},{"type":"text","text":"对象作为第一个参数的"},{"type":"codeinline","content":[{"type":"text","text":"DAO"}]},{"type":"text","text":"操作的执行，并且你需要在通知正文中访问该帐户。你可以编写以下内容："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation() && args(account,..)\")\npublic void validateAccount(Account account) {\n // ...\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"切入点表达式的"},{"type":"codeinline","content":[{"type":"text","text":"args(account，..)"}]},{"type":"text","text":"部分有两个用途。首先，它将匹配限制为仅方法采用至少一个参数且传递给该参数的参数为"},{"type":"codeinline","content":[{"type":"text","text":"Account"}]},{"type":"text","text":"实例的那些方法执行。其次，它通过"},{"type":"codeinline","content":[{"type":"text","text":"account"}]},{"type":"text","text":"参数使实际的"},{"type":"codeinline","content":[{"type":"text","text":"Account"}]},{"type":"text","text":"对象可用于通知。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"写这个的另一种方法是声明一个切入点，当它匹配一个连接点时提供"},{"type":"codeinline","content":[{"type":"text","text":"Account"}]},{"type":"text","text":"对象值，然后从通知中引用命名的切入点。如下所示："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Pointcut(\"com.xyz.myapp.SystemArchitecture.dataAccessOperation() && args(account,..)\")\nprivate void accountDataAccessOperation(Account account) {}\n\n@Before(\"accountDataAccessOperation(account)\")\npublic void validateAccount(Account account) {\n // ...\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有关更多详细信息，请参见"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"编程指南。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"代理对象（"},{"type":"codeinline","content":[{"type":"text","text":"this"}]},{"type":"text","text":"）、目标对象（"},{"type":"codeinline","content":[{"type":"text","text":"target"}]},{"type":"text","text":"）和注解（"},{"type":"codeinline","content":[{"type":"text","text":"@within"}]},{"type":"text","text":"，"},{"type":"codeinline","content":[{"type":"text","text":"@target"}]},{"type":"text","text":"，"},{"type":"codeinline","content":[{"type":"text","text":"@annotation"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"@args"}]},{"type":"text","text":"）都可以以类似的方式绑定。接下来的两个示例显示如何匹配使用"},{"type":"codeinline","content":[{"type":"text","text":"@Auditable"}]},{"type":"text","text":"注解的方法的执行并提取审计代码："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这两个示例中的第一个显示了"},{"type":"codeinline","content":[{"type":"text","text":"@Auditable"}]},{"type":"text","text":"注解的定义："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Retention(RetentionPolicy.RUNTIME)\n@Target(ElementType.METHOD)\npublic @interface Auditable {\n AuditCode value();\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这两个示例中的第二个示例显示了与"},{"type":"codeinline","content":[{"type":"text","text":"@Auditable"}]},{"type":"text","text":"方法的执行相匹配的通知："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(\"com.xyz.lib.Pointcuts.anyPublicMethod() && @annotation(auditable)\")\npublic void audit(Auditable auditable) {\n AuditCode code = auditable.value();\n // ...\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"通知参数和泛型"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Spring AOP可以处理类声明和方法参数中使用的泛型。假设你具有如下通用类型："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"public interface Sample {\n void sampleGenericMethod(T param);\n void sampleGenericCollectionMethod(Collection param);\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以通过在要拦截方法的参数类型中键入advice参数，将方法类型的拦截限制为某些参数类型："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(\"execution(* ..Sample+.sampleGenericMethod(*)) && args(param)\")\npublic void beforeSampleMethod(MyType param) {\n // Advice implementation\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这种方法不适用于泛型集合。因此，你不能按以下方式定义切入点："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(\"execution(* ..Sample+.sampleGenericCollectionMethod(*)) && args(param)\")\npublic void beforeSampleMethod(Collection param) {\n // Advice implementation\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"为了使这项工作有效，我们将不得不检查集合的每个元素，这是不合理的，因为我们也无法决定通常如何处理"},{"type":"codeinline","content":[{"type":"text","text":"null"}]},{"type":"text","text":"。要实现类似的目的，你必须将参数键入"},{"type":"codeinline","content":[{"type":"text","text":"Collection >"}]},{"type":"text","text":"并手动检查元素的类型。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"确定参数名称"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通知调用中的参数绑定依赖于切入点表达式中使用的名称与通知和切入点方法签名中声明的参数名称的匹配。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通过Java反射无法获得参数名称，因此Spring AOP使用以下策略来确定参数名称："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果用户已明确指定参数名称，则使用指定的参数名称。通知和切入点注解均具有可选的"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性，你可以使用该属性来指定带注解的方法的参数名称。这些参数名称在运行时可用。以下示例显示如何使用"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(value=\"com.xyz.lib.Pointcuts.anyPublicMethod() && target(bean) && @annotation(auditable)\",\n argNames=\"bean,auditable\")\npublic void audit(Object bean, Auditable auditable) {\n AuditCode code = auditable.value();\n // ... use code and bean\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果第一个参数是"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}]},{"type":"text","text":"、"},{"type":"codeinline","content":[{"type":"text","text":"ProceedingJoinPoint"}]},{"type":"text","text":"或"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint.StaticPart"}]},{"type":"text","text":"类型，则可以从"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性的值中忽略该参数的名称。例如，如果你修改前面的通知以接收连接点对象，则"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性不需要包括它："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(value=\"com.xyz.lib.Pointcuts.anyPublicMethod() && target(bean) && @annotation(auditable)\",\n argNames=\"bean,auditable\")\npublic void audit(JoinPoint jp, Object bean, Auditable auditable) {\n AuditCode code = auditable.value();\n // ... use code, bean, and jp\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"对"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint"}]},{"type":"text","text":"、"},{"type":"codeinline","content":[{"type":"text","text":"ProceedingJoinPoint"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"JoinPoint.StaticPart"}]},{"type":"text","text":"类型的第一个参数给予的特殊处理对于不收集任何其他连接点上下文的通知实例特别方便。在这种情况下，你可以省略"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性。例如，以下通知无需声明"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"属性："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Before(\"com.xyz.lib.Pointcuts.anyPublicMethod()\")\npublic void audit(JoinPoint jp) {\n // ... use jp\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用'"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"'属性有点笨拙，因此，如果未指定'"},{"type":"codeinline","content":[{"type":"text","text":"argNames"}]},{"type":"text","text":"'属性，Spring AOP将查找该类的调试信息，并尝试从局部变量表中确定参数名称。只要已使用调试信息（至少是"},{"type":"codeinline","content":[{"type":"text","text":" -g：vars"}]},{"type":"text","text":"）编译了类，此信息就会存在。 启用此标志时进行编译的后果是：（1）你的代码稍微易于理解（逆向工程），（2）类文件的大小略大（通常无关紧要），（3）编译器未应用删除未使用的局部变量的优化。换句话说，通过启用该标志，你应该不会遇到任何困难。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果在没有必要调试信息的情况下编译了代码，Spring AOP将尝试推断绑定变量与参数的配对（例如，如果切入点表达式中仅绑定了一个变量，并且advice方法仅接受一个参数，则配对很明显）。如果在给定可用信息的情况下变量的绑定不明确，则抛出"},{"type":"codeinline","content":[{"type":"text","text":"AmbiguousBindingException"}]},{"type":"text","text":"。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果以上所有策略均失败，则抛出"},{"type":"codeinline","content":[{"type":"text","text":"IllegalArgumentException"}]},{"type":"text","text":"。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"proceed参数"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"前面我们提到过，我们将描述如何编写一个在Spring AOP和"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"中始终有效的参数的"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"调用。解决方案是确保通知签名按顺序绑定每个方法参数。以下示例显示了如何执行此操作："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Around(\"execution(List find*(..)) && \" +\n \"com.xyz.myapp.SystemArchitecture.inDataAccessLayer() && \" +\n \"args(accountHolderNamePattern)\")\npublic Object preProcessQueryPattern(ProceedingJoinPoint pjp,\n String accountHolderNamePattern) throws Throwable {\n String newPattern = preProcess(accountHolderNamePattern);\n return pjp.proceed(new Object[] {newPattern});\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在许多情况下，无论如何都要进行此绑定（如上例所示）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"通知顺序"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当多条通知都希望在同一连接点上运行时会发生什么？ Spring AOP遵循与"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"相同的优先级规则来确定通知执行的顺序。优先级最高的通知在进入时首先运行(因此，给定两个"},{"type":"codeinline","content":[{"type":"text","text":"before"}]},{"type":"text","text":"通知，优先级最高的通知首先运行)。在从连接点出来的过程中，优先级最高的通知最后运行(因此，给定两个"},{"type":"codeinline","content":[{"type":"text","text":"after"}]},{"type":"text","text":"通知，优先级最高的通知将排在第二)。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在不同切面定义的两个通知都需要在同一个连接点上运行时，除非另行指定，否则执行顺序是未定义的。你可以通过指定优先级来控制执行顺序。通过在切面类中实现"},{"type":"codeinline","content":[{"type":"text","text":"org.springframework.core.Ordered"}]},{"type":"text","text":"接口或使用Order注解对其进行注解，可以通过常规的Spring方法来完成。给定两个切面，从"},{"type":"codeinline","content":[{"type":"text","text":"Ordered.getValue()"}]},{"type":"text","text":"（或注解值）返回较低值的切面具有较高的优先级"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"当在同一个切面中定义的两个通知都需要在同一个连接点上运行时，顺序是未定义的(因为无法通过java编译类的反射检索声明顺序)。考虑将此类通知方法分解为每个切面类中的每个连接点的一个通知方法，或者将通知片段重构为可以在切面级别排序的单独切面类。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.5 引入"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"引入(在AspectJ中称为类型间声明)使能够声明已通知的对象实现给定接口，并代表这些对象提供该接口的实现。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以使用"},{"type":"codeinline","content":[{"type":"text","text":"@DeclareParents"}]},{"type":"text","text":"注解进行介绍。此注解用于声明匹配类型具有新的父类（因此具有名称）。例如，给定一个名为"},{"type":"codeinline","content":[{"type":"text","text":"UsageTracked"}]},{"type":"text","text":"的接口和该接口的一个名为"},{"type":"codeinline","content":[{"type":"text","text":"DefaultUsageTracked"}]},{"type":"text","text":"的实现，下面的切面声明了服务接口的所有实现者也实现了"},{"type":"codeinline","content":[{"type":"text","text":"UsageTracked"}]},{"type":"text","text":"接口(例如通过"},{"type":"codeinline","content":[{"type":"text","text":"JMX"}]},{"type":"text","text":"公开统计信息)："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Aspect\npublic class UsageTracking {\n\n @DeclareParents(value=\"com.xzy.myapp.service.*+\", defaultImpl=DefaultUsageTracked.class)\n public static UsageTracked mixin;\n\n @Before(\"com.xyz.myapp.SystemArchitecture.businessService() && this(usageTracked)\")\n public void recordUsage(UsageTracked usageTracked) {\n usageTracked.incrementUseCount();\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"要实现的接口由带注解的字段的类型确定。"},{"type":"codeinline","content":[{"type":"text","text":"@DeclareParents"}]},{"type":"text","text":"注解的"},{"type":"codeinline","content":[{"type":"text","text":"value"}]},{"type":"text","text":"属性是"},{"type":"codeinline","content":[{"type":"text","text":"AspectJ"}]},{"type":"text","text":"类型的模式。匹配类型的任何bean都实现"},{"type":"codeinline","content":[{"type":"text","text":"UsageTracked"}]},{"type":"text","text":"接口。注意，在前面示例的"},{"type":"codeinline","content":[{"type":"text","text":"before"}]},{"type":"text","text":"通知中，服务bean可以直接用作"},{"type":"codeinline","content":[{"type":"text","text":"UsageTracked"}]},{"type":"text","text":"接口的实现。如果以编程方式访问bean，则应编写以下内容："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"UsageTracked usageTracked = (UsageTracked) context.getBean(\"myService\");\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"参考代码："},{"type":"codeinline","content":[{"type":"text","text":"com.liyong.ioccontainer.starter.AopDeclareParentsIocContiner"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.6 切面实例化模型"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这是一个高级主题。如果你刚开始使用AOP，则可以放心地跳过它，直到以后。"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"默认情况下，应用程序上下文中每个切面都有一个实例。 AspectJ将此称为单例实例化模型。可以使用bean生命周期来定义切面。Spring支持AspectJ的"},{"type":"codeinline","content":[{"type":"text","text":"perthis"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"pertarget"}]},{"type":"text","text":"实例化模型（当前不支持"},{"type":"codeinline","content":[{"type":"text","text":"percflow"}]},{"type":"text","text":"，"},{"type":"codeinline","content":[{"type":"text","text":"percflowbelow"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"pertypewithin"}]},{"type":"text","text":"）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"你可以通过在"},{"type":"codeinline","content":[{"type":"text","text":"@Aspect"}]},{"type":"text","text":"注解中指定"},{"type":"codeinline","content":[{"type":"text","text":"perthis"}]},{"type":"text","text":"来声明"},{"type":"codeinline","content":[{"type":"text","text":"perthis"}]},{"type":"text","text":"切面。考虑以下示例："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Aspect(\"perthis(com.xyz.myapp.SystemArchitecture.businessService())\")\npublic class MyAspect {\n\n private int someState;\n\n @Before(com.xyz.myapp.SystemArchitecture.businessService())\n public void recordServiceUsage() {\n // ...\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在前面的示例中，“ "},{"type":"codeinline","content":[{"type":"text","text":"perthis"}]},{"type":"text","text":"”子句的作用是为每个执行业务服务的唯一服务对象（每个与切入点表达式匹配的连接点绑定到“ "},{"type":"codeinline","content":[{"type":"text","text":"this"}]},{"type":"text","text":"”的唯一对象）创建一个切面实例。切面实例是在服务对象上首次调用方法时创建的。当服务对象超出范围时，切面将超出范围。在创建切面实例之前，其中的任何通知都不会执行。一旦创建了切面实例，在其中声明的通知就会在匹配的连接点上执行，但仅当服务对象与此切面相关联时才执行。有关每个子句的更多信息，请参见AspectJ编程指南。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"pertarget"}]},{"type":"text","text":"实例化模型的工作方式与"},{"type":"codeinline","content":[{"type":"text","text":"perthis"}]},{"type":"text","text":"完全相同，但是它在匹配的连接点为每个唯一目标对象创建一个切面实例。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"5.4.7 AOP例子"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"现在你已经了解了所有组成部分是如何工作的，我们可以将它们组合在一起做一些有用的事情。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有时由于并发问题（例如，死锁失败），业务服务的执行可能会失败。如果重试该操作，则很可能在下一次尝试中成功。对于适合在这种情况下重试的业务服务（不需要为解决冲突而需要返回给用户的幂等操作），我们希望透明地重试该操作，以避免客户端看到"},{"type":"codeinline","content":[{"type":"text","text":"PessimisticLockingFailureException"}]},{"type":"text","text":"。这是一个明显跨越服务层中的多个服务的需求，因此非常适合通过切面实现。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"因为我们想重试该操作，所以我们需要使用环绕通知，以便可以多次调用"},{"type":"codeinline","content":[{"type":"text","text":"proceed"}]},{"type":"text","text":"。以下清单显示了基本切面的实现："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Aspect\npublic class ConcurrentOperationExecutor implements Ordered {\n\n private static final int DEFAULT_MAX_RETRIES = 2;\n\n private int maxRetries = DEFAULT_MAX_RETRIES;\n private int order = 1;\n\n public void setMaxRetries(int maxRetries) {\n this.maxRetries = maxRetries;\n }\n\n public int getOrder() {\n return this.order;\n }\n\n public void setOrder(int order) {\n this.order = order;\n }\n\n @Around(\"com.xyz.myapp.SystemArchitecture.businessService()\")\n public Object doConcurrentOperation(ProceedingJoinPoint pjp) throws Throwable {\n int numAttempts = 0;\n PessimisticLockingFailureException lockFailureException;\n do {\n numAttempts++;\n try {\n return pjp.proceed();\n }\n catch(PessimisticLockingFailureException ex) {\n lockFailureException = ex;\n }\n } while(numAttempts <= this.maxRetries);\n throw lockFailureException;\n }\n\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"请注意，切面实现了"},{"type":"codeinline","content":[{"type":"text","text":"Ordered"}]},{"type":"text","text":"接口，以便我们可以将切面的优先级设置为高于事务通知的优先级(每次重试时都需要一个新的事务)。"},{"type":"codeinline","content":[{"type":"text","text":"maxRetries"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"order"}]},{"type":"text","text":"属性均由Spring配置。通知的主要动作发生在"},{"type":"codeinline","content":[{"type":"text","text":"doConcurrentOperation"}]},{"type":"text","text":"中。请注意，目前，我们将重试逻辑应用于每个"},{"type":"codeinline","content":[{"type":"text","text":"businessService()"}]},{"type":"text","text":"。我们尝试继续，如果失败并出现"},{"type":"codeinline","content":[{"type":"text","text":"PessimisticLockingFailureException"}]},{"type":"text","text":"，则我们将再次重试，除非我们用尽了所有重试尝试。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"对应的Spring配置如下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"html"},"content":[{"type":"text","text":"\n\n\n \n \n\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"为了完善切面，使其仅重试幂等操作，我们可以定义以下幂等注解："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Retention(RetentionPolicy.RUNTIME)\npublic @interface Idempotent {\n // marker annotation\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"然后，我们可以使用注解来注释服务操作的实现。切面更改为仅重试幂等操作涉及更改切入点表达式，以便仅"},{"type":"codeinline","content":[{"type":"text","text":"@Idempotent"}]},{"type":"text","text":"操作匹配，如下所示："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"@Around(\"com.xyz.myapp.SystemArchitecture.businessService() && \" +\n \"@annotation(com.xyz.myapp.service.Idempotent)\")\npublic Object doConcurrentOperation(ProceedingJoinPoint pjp) throws Throwable {\n // ...\n}\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"作者"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"个人从事金融行业，就职过易极付、思建科技、某网约车平台等重庆一流技术团队，目前就职于某银行负责统一支付系统建设。自身对金融行业有强烈的爱好。同时也实践大数据、数据存储、自动化集成和部署、分布式微服务、响应式编程、人工智能等领域。同时也热衷于技术分享创立公众号和博客站点对知识体系进行分享。关注公众号："},{"type":"text","marks":[{"type":"strong"}],"text":"青年IT男"},{"type":"text","text":" 获取最新技术文章推送！"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"博客地址："},{"type":"text","text":" "},{"type":"link","attrs":{"href":"http://youngitman.tech/","title":null},"content":[{"type":"text","text":"http://youngitman.tech"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"CSDN："},{"type":"text","text":" "},{"type":"link","attrs":{"href":"https://blog.csdn.net/liyong1028826685","title":null},"content":[{"type":"text","text":"https://blog.csdn.net/liyong1028826685"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"微信公众号："},{"type":"text","text":" "}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/0e/0e1ef0e34fb3ecf6b6c553250015a224.jpeg","alt":null,"title":"","style":[{"key":"width","value":"25%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}