java - 如何在不使用构造函数的情况下初始化 AspectJ 切面？

Question

我的 AspectJ 方面看起来像这样:

@Aspect
public class MyAspect {
  private Child child;
  public MyAspect() {
    this.child = new Child();
  }
  @Around("... skipped ...")
  public Object wrap(ProceedingJoinPoint point) throws Throwable {
    // some custom functionality
    return point.proceed();
  }
}

这是行不通的，因为在 Child 的构造过程中调用了一个 wrap() 切入点并导致运行时异常，因为 的实例MyAspect 尚未就绪。

是否可以告诉 AspectJ 在实例化后立即调用 MyAspect 的某些方法？

Answer 1

新答案:

这是一个示例驱动程序类 Child:

public class Child {
    private String name;

    public Child(String name) {
        this.name = name;
        System.out.println("Constructing child named " + this.name);
    }

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public static void main(String[] args) {
        Child myChild = new Child("Penélope");
        System.out.println("My child is named " + myChild.getName());
        myChild.setName("María Elena");
        System.out.println("My child is now named " + myChild.getName());
    }
}

这是一个切面 MyAspect 拦截 Child 的公共(public)方法和构造函数执行，但不包括切面构造函数:

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class MyAspect {
    private Child child;

    public MyAspect() {
        child = new Child("Scarlett");
        System.out.println("Aspect child is named " + child.getName());
        child.setName("Cristina");
        System.out.println("Aspect child is now named " + child.getName());
    }

    @Around(
        "(execution(public * Child.*(..)) || execution(public Child.new(..)))" +
        "&& !cflow(initialization(MyAspect.new()))"
    )
    public Object wrap(ProceedingJoinPoint point) throws Throwable {
        System.out.println(point.getStaticPart());
        return point.proceed();
    }
}

这是示例输出:

Constructing child named Scarlett
Aspect child is named Scarlett
Aspect child is now named Cristina
execution(void Child.main(String[]))
execution(Child(String))
Constructing child named Penélope
execution(String Child.getName())
My child is named Penélope
execution(void Child.setName(String))
execution(String Child.getName())
My child is now named María Elena

您可以看到在切面构造期间没有拦截任何 Child 连接点。顺便说一句，否则您无论如何都会得到 NoAspectBoundException。 ;-)

---

旧答案:

您可以将您的切入点与类似(未测试)的内容结合起来:

... && !cflow(MyAspect.new())

这应该排除您不想拦截的内容。