Bytebuddy - 拦截 java.net.ServerSocket 构造函数

Question

我正在尝试拦截 java.net.ServerSocket 的两个方法和一个构造函数。拦截 getLocalPort 和 getInetAddress 这两种方法可以正常工作。然而，应该处理构造函数 ServerSocket(int) 的 class 没有被触发。我要检测的代码（在主项目中包含的不同 jar 文件中）：

包检测；

public class Instrumenting {

    private static final String CLASS_NAME = "java.net.ServerSocket";

    public static void instrument(Instrumentation instrumentation) throws Exception {
        System.out.println("[Instrumenting] starting to instrument '" + CLASS_NAME + "'");

        instrumentation.appendToBootstrapClassLoaderSearch(new JarFile("C:\Users\Moritz\Instrumenting\dist\Instrumenting.jar"));

        File temp = Files.createTempDirectory("tmp").toFile();
        ClassInjector.UsingInstrumentation.of(temp, ClassInjector.UsingInstrumentation.Target.BOOTSTRAP, instrumentation).inject(Collections.singletonMap(
            new TypeDescription.ForLoadedType(GetLocalPortIntercept.class),
            ClassFileLocator.ForClassLoader.read(GetLocalPortIntercept.class)));


        new AgentBuilder.Default()
                .ignore(ElementMatchers.none())
                .with(new AgentBuilder.InjectionStrategy.UsingInstrumentation(instrumentation, temp))
                .type(ElementMatchers.named(CLASS_NAME))

                .transform((DynamicType.Builder<?> builder, TypeDescription td, ClassLoader cl, JavaModule jm) -> 
                        builder
                                .method(ElementMatchers.named("getLocalPort"))
                                .intercept(MethodDelegation.to(GetLocalPortIntercept.class))

                                .method(ElementMatchers.named("getInetAddress"))
                                .intercept(MethodDelegation.to(GetInetAddressIntercept.class))

                                .constructor(ElementMatchers.takesArguments(1).and(ElementMatchers.takesArguments(Integer.class)))
                                .intercept(MethodDelegation.to(ServerSocketIntercept.class))
                ).installOn(instrumentation);

        System.out.println("[Instrumenting] done");
    }

    public static class ServerSocketIntercept {

        public static void intercept(int port) throws Exception {
            System.out.println("[ServerSocketIntercept] port: " + port);
        }

    }

    public static class GetLocalPortIntercept {

        public static int intercept() throws Exception {
            System.out.println("[GetLocalPortIntercept]");

            return 42;
        }

    }

    public static class GetInetAddressIntercept {

        public static InetAddress intercept() throws Exception {
            System.out.println("[GetInetAddressIntercept]");

            return InetAddress.getByAddress(new byte[] {1, 2, 3 ,4});
        }

    }
}

如何计算：

import instrumenting.Instrumenting;

...


public class Main {

    public static void premain(String agentArgs, Instrumentation instrumentation) throws Exception {
        Instrumenting.instrument(instrumentation);
    }

    public static void main(String[] args) throws MalformedURLException, IOException {
        ServerSocket serverSocket = new ServerSocket(12345);
        System.out.println("Localport: " + serverSocket.getLocalPort());
        System.out.println("InetAddress: " + serverSocket.getInetAddress());
    }
}

输出：

[Instrumentation] starting to instrument 'java.net.ServerSocket'
[Instrumentation] done 
[GetLocalPortIntercept] Localport: 42
[GetInetAddressIntercept] InetAddress: /1.2.3.4

如您所见，

拦截 getLocalPort 和 getInetAddress 效果很好。但是为什么构造函数没有被拦截？

Answer 1

这是因为 ServerSocket 接受 int 而不是 Integer。但是，如果您尝试这样做，它会崩溃，因为 JVM 需要硬编码到任何构造函数中的超级方法调用。您需要运行: SuperMethodCall.INSTANCE.andThen(...) 在实际拦截之前才能使其正常工作。

一般来说，我建议您对 JVM 类上的此类 bootstrap 代理使用 Advice，您可以在其中将代码内联到目标中。会更稳健。

Bytebuddy - 拦截 java.net.ServerSocket 构造函数

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