如何编写可中断的方法

Question

我有一种方法,从概念上看,它看起来像:

Object f(Object o1) {
    Object o2 = longProcess1(o1);
    Object o3 = longProcess2(o2);
    return longProcess3(o3);
}

过程本身也可能是复合的:

Object longProcess1(Object o1) {
    Object o2 = longSubProcess1(o1);
    return longSubProcess2(o2);
}

等等,不同的过程可能存在于不同的模块中.大多数进程都很长,因为它们计算成本高,而不是IO绑定.

到目前为止f一切都那么好,但现在我想整体上是可以打断的.推荐的Java方法是定期检查中断标志Thread.interrupted().它非常简单,但如果我需要将我的方法更改为以下内容,它很快就会变得很麻烦:

Object f(Object o1) {
    Object o2 = longProcess1(o1);
    if (Thread.interrupted()) throw new InterruptedException();
    Object o3 = longProcess2(o2);
    if (Thread.interrupted()) throw new InterruptedException();
    return longProcess3(o3);
}

Object longProcess1(Object o1) {
    Object o2 = longSubProcess1(o1);
    if (Thread.interrupted()) throw new InterruptedException();
    return longSubProcess2(o2);
}

...

现在,我确实理解了这样工作的理性 - 它允许我更好地控制何时抛出InterruptedException(例如),避免让对象处于不一致状态 - 但我很想知道是否有更优雅的做法*.

*在Java中,不是AspectJ,我认为这是非常合适的,但我坚持使用Java.

Answer 1

您可以使用接口和动态代理:

public class Wrapper {
    public static <T> T wrap(Class<T> intf, final T impl) {
        ClassLoader cl = Thread.currentThread().getContextClassLoader();
        Object proxy = Proxy.newProxyInstance(cl, new Class<?>[] {intf},
                new InvocationHandler() {
            public Object invoke(Object proxy, Method method, Object[] args)
                    throws Throwable {
                if (Thread.interrupted()) {
                    throw new InterruptedException();
                }
                return method.invoke(impl, args);
            }
        });
        return intf.cast(proxy);
    }
}

interface Processes {
    Object longProcess1(Object o);
    ...
}

public class ProcessesImpl implement Processes {
    Processes self = Wrapper.wrap(Processes.class, this);

    public Object f(Object o1) {
        Object o2 = self.longProcess1(o1);
        Object o3 = self.longProcess2(o2);
        return self.longProcess3(o3);
    }

    public Object longProcess1(Object o1) {
        Object o2 = self.longSubProcess1(o1);
        return self.longSubProcess2(o2);
    }

    ....
}