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java - Bytebuddy - 拦截 java.net.ServerSocket 构造函数

问题描述

我试图拦截java.net.ServerSocket. 拦截这两种方法getLocalPort并且getInetAddress工作正常。ServerSocket(int)但是，不会触发应该处理构造函数的类。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});
        }

    }
}

它是如何命名的：

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和工作正常。getInetAddress但是为什么构造函数没有被拦截呢？

标签： javabytecodebyte-buddy

解决方案

这是因为ServerSocket接受 anint而不是Integer. 但是，如果您尝试这样做，它会崩溃，因为 JVM 需要将超级方法调用硬编码到任何构造函数中。您需要运行：SuperMethodCall.INSTANCE.andThen(...)在实际拦截之前使其工作。

一般来说，我建议您Advice在 JVM 类上使用此类引导代理，您可以在其中将代码内联到目标中。它会更健壮。

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