如何使用AspectJ拦截处理自身exception的方法
我正在尝试在发生某些特定exception时添加一些监控。 例如，如果我有这样的方面：
@Aspect public class LogAspect { @AfterThrowing(value = "execution(* *(..))", throwing = "e") public void log(JoinPoint joinPoint, Throwable e){ System.out.println("Some logging stuff"); } } 和测试类：
public class Example { public void divideByZeroWithCatch(){ try{ int a = 5/0; } catch (ArithmeticException e){ System.out.println("Can not divide by zero"); } } public void divideByZeroWithNoCatch(){ int b = 5/0; } public static void main (String [] args){ Example e = new Example(); System.out.println("***** Calling method with catch block *****"); e.divideByZeroWithCatch(); System.out.println("***** Calling method without catch block *****"); e.divideByZeroWithNoCatch(); } }
作为输出我会得到：
***** Calling method with catch block ***** Can not divide by zero ***** Calling method without catch block ***** Some logging stuff
我想知道是否有方法让我在抛出exception后拦截方法执行，在我的建议中做一些事情并继续在相应的catch块中执行代码？ 所以，如果我调用divideByZeroWithCatch()我可以得到：
Some logging stuff Can not divide by zero
是的你可以。 你需要一个handler()切入点：
package de.scrum_master.aspect; import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.AfterThrowing; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; @Aspect public class LogAspect { @AfterThrowing(value = "execution(* *(..))", throwing = "e") public void log(JoinPoint thisJoinPoint, Throwable e) { System.out.println(thisJoinPoint + " -> " + e); } @Before("handler(*) && args(e)") public void logCaughtException(JoinPoint thisJoinPoint, Exception e) { System.out.println(thisJoinPoint + " -> " + e); } }
日志输出，假设类Example在包de.scrum_master.app ：
***** Calling method with catch block ***** handler(catch(ArithmeticException)) -> java.lang.ArithmeticException: / by zero Can not divide by zero ***** Calling method without catch block ***** execution(void de.scrum_master.app.Example.divideByZeroWithNoCatch()) -> java.lang.ArithmeticException: / by zero execution(void de.scrum_master.app.Example.main(String[])) -> java.lang.ArithmeticException: / by zero Exception in thread "main" java.lang.ArithmeticException: / by zero at de.scrum_master.app.Example.divideByZeroWithNoCatch(Example.java:13) at de.scrum_master.app.Example.main(Example.java:21)
更新：如果您想知道exception处理程序的位置，有一种简单的方法：使用封闭的连接点的静态部分。 您还可以获取有关参数名称和类型等的信息。只需使用代码完成以查看可用的方法。
@Before("handler(*) && args(e)") public void logCaughtException( JoinPoint thisJoinPoint, JoinPoint.EnclosingStaticPart thisEnclosingJoinPointStaticPart, Exception e ) { // Exception handler System.out.println(thisJoinPoint.getSignature() + " -> " + e); // Method signature + parameter types/names MethodSignature methodSignature = (MethodSignature) thisEnclosingJoinPointStaticPart.getSignature(); System.out.println(" " + methodSignature); Class[] paramTypes = methodSignature.getParameterTypes(); String[] paramNames = methodSignature.getParameterNames(); for (int i = 0; i < paramNames.length; i++) System.out.println(" " + paramTypes[i].getName() + " " + paramNames[i]); // Method annotations - attention, reflection! Method method = methodSignature.getMethod(); for (Annotation annotation: method.getAnnotations()) System.out.println(" " + annotation); }
现在更新您的代码，如下所示：
package de.scrum_master.app; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; @Retention(RetentionPolicy.RUNTIME) public @interface MyAnnotation { int id(); String name(); String remark(); }
package de.scrum_master.app; public class Example { @MyAnnotation(id = 11, name = "John", remark = "my best friend") public void divideByZeroWithCatch(int dividend, String someText) { try { int a = 5 / 0; } catch (ArithmeticException e) { System.out.println("Can not divide by zero"); } } public void divideByZeroWithNoCatch() { int b = 5 / 0; } public static void main(String[] args) { Example e = new Example(); System.out.println("***** Calling method with catch block *****"); e.divideByZeroWithCatch(123, "Hello world!"); System.out.println("***** Calling method without catch block *****"); e.divideByZeroWithNoCatch(); } }
然后控制台日志说：
***** Calling method with catch block ***** catch(ArithmeticException) -> java.lang.ArithmeticException: / by zero void de.scrum_master.app.Example.divideByZeroWithCatch(int, String) int dividend java.lang.String someText @de.scrum_master.app.MyAnnotation(id=11, name=John, remark=my best friend) Can not divide by zero ***** Calling method without catch block ***** execution(void de.scrum_master.app.Example.divideByZeroWithNoCatch()) -> java.lang.ArithmeticException: / by zero execution(void de.scrum_master.app.Example.main(String[])) -> java.lang.ArithmeticException: / by zero Exception in thread "main" java.lang.ArithmeticException: / by zero at de.scrum_master.app.Example.divideByZeroWithNoCatch(Example.java:14) at de.scrum_master.app.Example.main(Example.java:22)
如果这对你来说足够好，那你就没事了。 但要注意，静态部分不是完整的连接点，因此您无法从那里访问参数值。 为此，您必须进行手动记账。 这可能很昂贵，可能会降低您的应用程序速度。 但是为了它的价值，我告诉你如何做到这一点：
package de.scrum_master.aspect; import java.lang.annotation.Annotation; import java.lang.reflect.Method; import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.AfterThrowing; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.reflect.MethodSignature; @Aspect public class LogAspect { private ThreadLocal enclosingJoinPoint; @AfterThrowing(value = "execution(* *(..))", throwing = "e") public void log(JoinPoint thisJoinPoint, Throwable e) { System.out.println(thisJoinPoint + " -> " + e); } @Before("execution(* *(..)) && within(de.scrum_master.app..*)") public void recordJoinPoint(JoinPoint thisJoinPoint) { if (enclosingJoinPoint == null) enclosingJoinPoint = ThreadLocal.withInitial(() -> thisJoinPoint); else enclosingJoinPoint.set(thisJoinPoint); } @Before("handler(*) && args(e)") public void logCaughtException(JoinPoint thisJoinPoint, Exception e) { // Exception handler System.out.println(thisJoinPoint + " -> " + e); // Method signature + parameter types/names JoinPoint enclosingJP = enclosingJoinPoint.get(); MethodSignature methodSignature = (MethodSignature) enclosingJP.getSignature(); System.out.println(" " + methodSignature); Class[] paramTypes = methodSignature.getParameterTypes(); String[] paramNames = methodSignature.getParameterNames(); Object[] paramValues = enclosingJP.getArgs(); for (int i = 0; i < paramNames.length; i++) System.out.println(" " + paramTypes[i].getName() + " " + paramNames[i] + " = " + paramValues[i]); // Target object upon which method is executed System.out.println(" " + enclosingJP.getTarget()); // Method annotations - attention, reflection! Method method = methodSignature.getMethod(); for (Annotation annotation: method.getAnnotations()) System.out.println(" " + annotation); } }
为什么我们需要一个ThreadLocal成员来进行连接点记录？ 好吧，因为很明显我们会在multithreading应用程序中遇到问题。
现在控制台日志说：
***** Calling method with catch block ***** handler(catch(ArithmeticException)) -> java.lang.ArithmeticException: / by zero void de.scrum_master.app.Example.divideByZeroWithCatch(int, String) int dividend = 123 java.lang.String someText = Hello world! de.scrum_master.app.Example@4783da3f @de.scrum_master.app.MyAnnotation(id=11, name=John, remark=my best friend) Can not divide by zero ***** Calling method without catch block ***** execution(void de.scrum_master.app.Example.divideByZeroWithNoCatch()) -> java.lang.ArithmeticException: / by zero execution(void de.scrum_master.app.Example.main(String[])) -> java.lang.ArithmeticException: / by zero Exception in thread "main" java.lang.ArithmeticException: / by zero at de.scrum_master.app.Example.divideByZeroWithNoCatch(Example.java:14) at de.scrum_master.app.Example.main(Example.java:22)
根据AspectJfunction的实际实现，它是可能的。 请参阅kriegaex的答案，了解如何做到这一点 。
但是，在某些情况下使用AspectJfunction时，您可能会发现并非所有切入点定义都受支持。 其中一个例子是Spring Framework AOP， 它只支持AspectJfunction的一个子集 。 你可以做的是有两种方法：一种不暴露但可检测的方法， 它不会捕获exception（你要检测的那种），以及暴露的捕获方法。 喜欢这个：
protected void divideByZeroNoCatch(int arg) { int r = arg / 0; } public void divideByZeroSafe(int arg) { try { divideByZeroNoCatch(arg); } catch(ArithmeticException ae) { logException(ae); } }
之后，您可以divideByZeroNoCatch ，这将使您能够进行AfterThrowing。 显然，切入点必须改变一点。 如果您对AspectJ的实现不支持检测非公共方法，那么这将不起作用。