Spring AOP - ProceedingJoinpoint - MethodSignature Downcast

Question

有没有办法从 ProceedingJoinPoint 获取 MethodSignature 而无需向下转换？

    private String toEventString(ProceedingJoinPoint pjp) {
    MethodSignature methodSignature = ((MethodSignature)pjp.getSignature());

    StringBuilder sb = new StringBuilder();

    String[] paramNames = methodSignature.getParameterNames();
    Class[] paramTypes = methodSignature.getParameterTypes();

    sb.append(methodSignature.getName()).append('(');

    for(int i = 0; i < paramNames.length; i++) {
        sb
            .append(paramTypes[i].getSimpleName())
            .append(" ")
            .append(paramNames[i]);
        if(i < paramNames.length - 1) {
            sb.append(", ");
        }
    }

    return sb.append(" )").toString();

}

Answer 1

简单的问题，简单的答案：不。

更新：也许您想知道为什么需要投射。除了方法签名，还有其他签名类型吗？哦，是的，有。例如。如果您使用within(SomeClass)，您可能会遇到以下任何签名类型：

• 方法
• 构造函数
• 类初始化器
• 字段
• 建议执行
• catch 子句
• 锁定/解锁（一种相当特殊的情况，如果方面是使用-Xjoinpoints:synchronization 编译的，则捕获同步块）

这是一个小例子：

驱动程序应用：

package de.scrum_master.app;

public class Application {
  private String name;

  public Application(String name) {
    this.name = name;
  }

  public static void main(String[] args) {
    Application application = new Application("my app");
    synchronized (application) {
      try {
        application.doSomething("foo", 11, false);
      }
      catch (RuntimeException e) {}
    }
  }

  private void doSomething(String string, int i, boolean b) {
    throw new RuntimeException("oops");
  }
}

Aspect 应该被拦截的通知执行：

package de.scrum_master.aspect;

public aspect MyOtherAspect {
  before() : execution(* main(..)) {}
}

方面打印签名类型：

package de.scrum_master.aspect;

import de.scrum_master.app.Application;

public aspect MyAspect {
  before() : within(Application) || within(MyOtherAspect) {
    System.out.println(thisJoinPoint);
    System.out.println("    " + thisJoinPoint.getSignature().getClass().getSimpleName());
  }
}

控制台日志：

staticinitialization(de.scrum_master.app.Application.<clinit>)
    InitializerSignatureImpl
staticinitialization(de.scrum_master.aspect.MyOtherAspect.<clinit>)
    InitializerSignatureImpl
preinitialization(de.scrum_master.aspect.MyOtherAspect())
    ConstructorSignatureImpl
initialization(de.scrum_master.aspect.MyOtherAspect())
    ConstructorSignatureImpl
execution(de.scrum_master.aspect.MyOtherAspect())
    ConstructorSignatureImpl
adviceexecution(void de.scrum_master.aspect.MyOtherAspect.before())
    AdviceSignatureImpl
execution(void de.scrum_master.app.Application.main(String[]))
    MethodSignatureImpl
call(de.scrum_master.app.Application(String))
    ConstructorSignatureImpl
preinitialization(de.scrum_master.app.Application(String))
    ConstructorSignatureImpl
initialization(de.scrum_master.app.Application(String))
    ConstructorSignatureImpl
execution(de.scrum_master.app.Application(String))
    ConstructorSignatureImpl
set(String de.scrum_master.app.Application.name)
    FieldSignatureImpl
lock(lock(Object))
    LockSignatureImpl
call(void de.scrum_master.app.Application.doSomething(String, int, boolean))
    MethodSignatureImpl
execution(void de.scrum_master.app.Application.doSomething(String, int, boolean))
    MethodSignatureImpl
call(java.lang.RuntimeException(String))
    ConstructorSignatureImpl
handler(catch(RuntimeException))
    CatchClauseSignatureImpl
unlock(unlock(Object))
    UnlockSignatureImpl

顺便说一句，每个*Impl 类都实现了相应的签名接口。