java是否可以使用ByteBuddy建议机制将本机方法封装在线程中？

2 年，4 月 Questions & Answers 87

我试图延迟写入单独线程中的socket，以使用javaagent模拟网络堆栈中的延迟。使用ByteBuddy，我设法装饰了本机java.net.SocketOutputStream::writeSocket0。然而，这样做，我暂停了当前线程，这不是我想要实现的。为了避免这个问题，我考虑创建一个线程，从中可以调用本机方法。不幸的是，我对ByteBuddy的了解仍然相当有限，我没有找到实现这一点的方法。我的最佳尝试如下所示：

//premain function
public static void premain(final String agentArgs, final Instrumentation instrumentation) {
    try{
        BootLoaderInjector.inject(DelayedExecutor.class);
        long duration = 100;

        new AgentBuilder.Default()
            .with(new ByteBuddy().with(Implementation.Context.Disabled.Factory.INSTANCE))
            .with(AgentBuilder.InitializationStrategy.NoOp.INSTANCE)
            .with(AgentBuilder.TypeStrategy.Default.REBASE)
            .enableNativeMethodPrefix("somePrefix")
            .with(AgentBuilder.Listener.StreamWriting.toSystemError().withErrorsOnly())
            .ignore(nameStartsWith("net.bytebuddy."))
            .type(named("java.net.SocketOutputStream"))
            .transform((transformer, typeDescription, classLoader, javaModule) ->
                transformer.method(named("socketWrite0"))
                    .intercept(
                        Advice.withCustomMapping().bind(Duration.class, duration)
                        .to(DelayInterceptor.class)
                )
            )
            .installOn(instrumentation);
    }
    catch (Throwable t){
        System.err.printf(t.getMessage());
    }
}

// interceptor class
public class DelayInterceptor {
    @Advice.OnMethodEnter
    public static void intercept(@SuperCall Callable<?> caller, @Duration long duration) {
        DelayedExecutor.execute(callable, duration);
    }
}

// execute the intercepted method in a new thread with a delay
public class DelayedExecutor implements Runnable {
    private final Callable<?> callable;
    private final long delay;

    private DelayedExecutor(Callable<?> callable, long delay) {
        this.callable = callable;
        this.delay = delay;
    }

    public static void execute(Callable<?> callable, long delay){
        new Thread(new DelayedExecutor(callable, delay)).start();
    }

    @Override
    public void run() {
        try {
            Thread.sleep(this.delay);
            this.callable.call();
        } catch (Exception ignore) {}
    }
}

但是，这失败了，因为@Callable不是AdviceAPI的一部分

不使用这些建议似乎会造成严重的限制。实际上，使用MethodDelegation会引发以下错误：

Registration of auxiliary types was disabled: net.bytebuddy.implementation.auxiliary.MethodCallProxy@3206bfce

有没有一种方法可以使用ByteBuddy的AdviceAPI将函数调用包装到块中

编辑

为了更清楚地说明问题并解决答案建议，下面是BootLoaderInjector.inject的实现，它显示了如何根据ClassInjector.UsingUnsafe.ofBootLoader()将类型添加到引导加载程序类加载程序中：

public class BootLoaderInjector {
    public static void inject(Class<?> targetClass) {
        try {
            ClassInjector.UsingUnsafe.ofBootLoader().inject(singletonMap(
                    new TypeDescription.ForLoadedType(targetClass),
                    ClassFileLocator.ForClassLoader.read(targetClass)
            ));
        } catch (Throwable e){
            System.out.println("Something went terribly wrong: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

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java是否可以使用ByteBuddy建议机制将本机方法封装在线程中？

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