我正在尝试使用基于Byte Buddy的Java代理来检测对javax. servlet.http.HttpServlet的service（）方法的调用。我代码中的premain函数被正确调用，但检测失败并导致堆栈跟踪：

java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at     sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at     sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at     sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:386)
  at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:401)
Caused by: java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
    at ub.jagent.ServletInstrumentation.instrument(ServletInstrumentation.java:24)
    at ub.jagent.StackTracerAgent.premain(StackTracerAgent.java:75)
    ... 6 more
Caused by: java.lang.ClassNotFoundException: javax.servlet.http.HttpServlet
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 8 more
FATAL ERROR in native method: processing of -javaagent failed

我使用代理生成器如下：

AgentBuilder b = new AgentBuilder.Default().ignore(ElementMatchers.none())
        .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
        .with(AgentBuilder.InitializationStrategy.NoOp.INSTANCE)
        .with(AgentBuilder.TypeStrategy.Default.REDEFINE)   
        .type(ElementMatchers.isSubTypeOf(HttpServlet.class))
            .transform((builder, type, classLoader) -> 
                builder.visit(Advice.to(ServletAdvice.class) 
                .on(ElementMatchers.named("service")
                .and(ElementMatchers.takesArgument(0, HttpServletRequest.class))
                .and(ElementMatchers.takesArgument(1, HttpServletResponse.class)))).installOn(inst);

我的建议实现如下所示：

public class ServletAdvice {

    @Advice.OnMethodEnter
    public static void before(@Advice.This Object obj,
                               @Advice.Argument(value = 0) HttpServletRequest a1,
                               @Advice.Argument(value = 1) HttpServletResponse a2,
                               @Advice.Origin Method method) 
        {
            System.out.println("\nRunning pre-method logic for " + obj.getClass().getCanonicalName() + ":" + method.getName() + "()");
        <...etc...>
        }
    }
}

奇怪的是，当我匹配特定的Tomcat实现类时：

.type(ElementMatchers.named("org.glassfish.jersey.servlet.ServletContainer"))

…然后代理设置就可以了（尽管在检测过程中，Adac方法中对HttpServletRequest和HttpServletResponse的引用会触发ClassNotFoundException）。

这是否意味着我必须在代理中包含所有代理依赖项（包括JavaServletAPI）。jar文件本身？

我正在使用ByteBuddy 1.6.2，Apache Tomcat v8.0。

编辑修订和工作代码（在拉斐尔的帮助下）如下所示：

         .type(ElementMatchers.isSubTypeOf(new TypeDescription.Latent("javax.servlet.GenericServlet", Modifier.PUBLIC | Modifier.ABSTRACT, TypeDescription.Generic.OBJECT, null)))
         .transform(
                 new AgentBuilder.Transformer.ForAdvice()
                    .include(getClass().getClassLoader())
                    .advice(
                        ElementMatchers.named("service")
                            .and(ElementMatchers.takesArgument(0, ElementMatchers.named("javax.servlet.http.HttpServletRequest"))
                            .and(ElementMatchers.takesArgument(1, ElementMatchers.named( "javax.servlet.http.HttpServletResponse")),
                        ServletAdvice.class.getName())
         );