如何劫持/拦截来自第三方(EclipseLink)jar 甚至 JDK 的类的方法? [英] How to hijacked/intercept method of a class which from third party(EclipseLink) jar or even JDK?

问题描述

我尝试劫持/拦截 EclipseLink 中某个类的方法.我曾尝试过 Spring AOP 和 AspectJ，但失败了.当 class org.eclipse.persistence.internal.localization.i18n.TraceLocalizationResource 在调用方法 getString(..); 时抛出异常时，我想做一些事情我的实现如下:

I try to hijack/intercept a method of a class in EclipseLink. I had tried Spring AOP and AspectJ and I failed. I want to do something when class org.eclipse.persistence.internal.localization.i18n.TraceLocalizationResource throw exception while calling method getString(..); My implementation as below:

@AfterThrowing(pointcut = "execution(* org.eclipse.persistence.internal.localization.i18n.TraceLocalizationResource.getString(..))",throwing="error")
    public void logAfterThrowing(JoinPoint joinPoint,Throwable error) {
....
}

并且调用了 calssTraceLocalizationResource(我调试它).但是没有调用劫持方法.

And calssTraceLocalizationResource was called (I debug into it). But the hijack method wasn't called.

我的问题:

1. 我做错了吗?
2. 我们要劫持或拦截的目标类必须是自定义类型吗?
3. 如果我想劫持像 java.lang.String 这样的 JDK 类怎么办?

推荐答案

1. 基本上语法看起来不错，但我没有尝试复制此处来自您的代码片段的完整方面.此外，我只使用原生 AspectJ 语法，我不太熟悉基于注释的语法，所以如果有问题，我可能不会看过了.

1. Basically the syntax looks okay, but I have not tried to replicate a full aspect from your code snippet here. Furthermore, I only use native AspectJ syntax and am not quite familiar with annotation-based syntax, so if there is a problem there I might not have seen it.

不可以，但是如果您想编织主应用程序使用的库(JAR 或解压到文件系统中)，您必须确保它位于编织器的路径中.请查阅 AspectJ 文档以了解语法.我今天早些时候在另一个答案中发布了一些有用的链接.

No, but if you want to weave a library (JAR or unpacked into the file system) used by your main application, you must make sure that it is in the in-path for the weaver. Please consult AspectJ documentation for the syntax. I posted some helpful links in another answer earlier today.

默认情况下，包org.aspectj、java 和javax 被排除在编织之外.对于后两者，有命令行开关来启用编织.但是 LTW 充其量是棘手的，最坏的情况是在 a**(几乎不可能)中痛苦，因为那里有一个鸡蛋和鸡蛋的问题:AspectJ weaver 运行时类需要 JDK，而 JDK 引导发生在任何 Java 之前像织布工一样的代理是附加的.因此，您最好的选择是在编译时编织 JDK 类，然后稍后在您的应用程序中使用编织的 rt.jar.即使使用编译时编织，如果您的建议本身使用 JDK 编织类，您也可能会遇到问题.您要确保避免在那里出现无限递归.但这是可能的.

By default, packages org.aspectj, java and javax are excluded from weaving. For the latter two, there are command line switches to enable weaving. But LTW will be tricky at best and a pain in the a** (next to impossible) at worst because you have a hen-and-egg problem there: The AspectJ weaver runtime classes need the JDK, and JDK bootstrapping happens before any Java agent like the weaver is attached. So your best bet is compile-time weaving for JDK classes and then using the woven rt.jar later in your application. Even with compile-time weaving you might run into issues if your advice use JDK woven classes themselves. You want to make sure to avoid infinite recursions there. But it is possible.

更新: 对于使用 AspectJ 一段时间的人来说，另一个提示有时似乎太简单而无法提及:而不是 execution 切入点，这使得必须编织目标类，您可以只使用 call 切入点，它拦截(顾名思义)对客户端类中任何地方的目标的调用.它可能效率稍低，但可能是您最好和最简单的选择，除非您真的想不厌其烦地编织 JDK.

Update: Another hint which sometimes seems too simple to mention for someone who has used AspectJ for a while: Instead of an execution pointcut which makes it necessary to weave the target class, you may just use a call pointcut which intercepts (as the name implies) calls to the target everywhere in your client classes. It might be a little less efficient, but maybe your best and easiest bet unless you really want to take the trouble of weaving the JDK.

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