Classpath problems while Instrumenting Springboot application

问题

I have a springboot application which I'm trying to instrument using bytebuddy. I'm running into classpath issues which I'm not able to understand.

Firstly, the following is other literature on this:

https://github.com/raphw/byte-buddy/issues/473

https://github.com/raphw/byte-buddy/issues/87

Unable to instrument apache httpclient using javaagent for spring boot uber jar application

https://github.com/raphw/byte-buddy/issues/109

https://github.com/raphw/byte-buddy/issues/473

https://github.com/raphw/byte-buddy/issues/489

https://github.com/spring-projects/spring-boot/issues/4868

https://github.com/alibaba/transmittable-thread-local/issues/161

Problem is that Spring-boot bundles the application into one uber-jar, which contains other jars inside it

A thing to note here is, that if I run the application using IntelliJ, it doesn't use the uber-jar and runs via main class with a bunch of jars as classpath arguments.

Due to this difference, When running via uber-jar(java -jar target/demo-0.0.1-SNAPSHOT.jar), some classes are not available at the time the Agent runs. The classes are loadable at the time of application main, as spring-boot uses its own classloader, which is created at some time b/w agent and application main methods.

I'll describe the behaviour at various points of time below:

At time of PreMain of Agent

Thread.currentThread().getContextClassLoader() = Launcher$AppClassLoader
Agent.class.classLoader = Launcher$AppClassLoader
Class.forName("org.springframework.web.servlet.HandlerAdapter") => ClassNotFoundException
Class.forName("javax.servlet.http.HttpServletRequest") => ClassNotFoundException

Both spring and javax classes are not loaded as they are not directly in the classpath as per the App Classloader. It's part of an inner jar, something like app.jar!/BOOT-INF/lib/some.jar App Classloader won't be able to load this.

At time of Main of Application Class

Thread.currentThread().getContextClassLoader() = org.springframework.boot.loader.LaunchedURLClassLoader
DemoApplication.class.classloader = same as above
Class.forName("org.springframework.web.servlet.HandlerAdapter") => loads successfully
Same for javax class, loads successfully.

After loading, Class.forName("javax.servlet.http.HttpServletRequest").classLoader is also the same LaunchedURLClassLoader.

At the time of `builder.visit` call (when bytebuddy is modifying the class definitions)

Code:

I have two classes, SpringBootInterceptor (which contains the intercept method) and SpringBootInterceptorOne (which contains the entry and exit method)

  @Override
  public AgentBuilder intercept(AgentBuilder agentBuilder) {
    return agentBuilder
      .type(isSubTypeOf(HandlerAdapter.class))
      .transform((builder, typeDescription, classLoader, module) ->
        builder.visit(Advice.to(SpringBootInterceptorOne.class, SpringBootInterceptorOne.class).on(named("handle").and(isMethod())))
      );
  }

The function intercept() is called in the premain path.

The function visit is called when the type is actually attempted to load. At that point bytebuddy tris to intercept those methods and modify bytecode.

In the current version of this code, the function intercept() throws ClassNotFoundException and interception doesn't happen.

Caused by: java.lang.NoClassDefFoundError: org/springframework/web/servlet/HandlerAdapter

So, I tried to change the code, to the following:

  @Override
  public AgentBuilder intercept(AgentBuilder agentBuilder) {
    return agentBuilder
//      .type(isSubTypeOf(HandlerAdapter.class))
      .type(not(isInterface())
        .and(safeHasSuperType(named("org.springframework.web.servlet.HandlerAdapter"))))
      .transform((builder, typeDescription, classLoader, module) ->
        builder.visit(Advice.to(SpringBootInterceptorOne.class, SpringBootInterceptorOne.class).on(named("handle").and(isMethod())))
      );
  }

Here, basically loading the class lazily. Helper functions from datadog:

https://github.com/DataDog/dd-trace-java/blob/master/dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/ByteBuddyElementMatchers.java

After doing this, the intercept function doesn't fail, but the visit() function behaves strangely:

java.lang.IllegalStateException: Could not locate class file for my.package.name.SpringBootInterceptorOne
    at net.bytebuddy.dynamic.ClassFileLocator$Resolution$Illegal.resolve(ClassFileLocator.java:118)
    at net.bytebuddy.asm.Advice.to(Advice.java:431)
    at net.bytebuddy.asm.Advice.to(Advice.java:400)
    at net.bytebuddy.asm.Advice.to(Advice.java:375)
    at net.bytebuddy.asm.Advice.to(Advice.java:361)
    at my.package.name.SpringBootInterceptor.lambda$intercept$0(SpringBootInterceptor.java:30)
    at net.bytebuddy.agent.builder.AgentBuilder$Transformer$Compound.transform(AgentBuilder.java:2612)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$Transformation$Simple$Resolution.apply(AgentBuilder.java:10117)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doTransform(AgentBuilder.java:10494)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10457)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.access$1500(AgentBuilder.java:10223)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:10833)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:10780)
    at java.security.AccessController.doPrivileged(Native Method)
    at net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:10380)
    at sun.instrument.TransformerManager.transform(TransformerManager.java:188)
    at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:428)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:757)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
    at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:92)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.getDeclaredMethods(Class.java:1975)
    at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:463)
    at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:358)
    at org.springframework.util.ReflectionUtils.getUniqueDeclaredMethods(ReflectionUtils.java:414)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.lambda$getTypeForFactoryMethod$2(AbstractAutowireCapableBeanFactory.java:743)
    at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1688)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:742)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:681)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:649)
    at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1604)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:520)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:491)
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.collectBeanNamesForType(OnBeanCondition.java:230)
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getBeanNamesForType(OnBeanCondition.java:223)
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getBeanNamesForType(OnBeanCondition.java:213)
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchingBeans(OnBeanCondition.java:167)
    at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:142)
    at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47)
    at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:108)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForBeanMethod(ConfigurationClassBeanDefinitionReader.java:184)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass(ConfigurationClassBeanDefinitionReader.java:144)
    at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClassBeanDefinitionReader.java:120)
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:331)
    at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:236)
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:275)
    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:95)
    at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:706)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
    at com.example.demo.DemoApplication.main(DemoApplication.java:10)
    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 org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:51)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:52)

At this point,

Thread.currentThread().getContextClassLoader() => LaunchedURLClassLoader
SpringBootInterceptor.class.getClassLoader() = null
Typing SpringBootInterceptor.class in the debugger window doesn't fail, but
Class.forName("my.package.name.SpringBootInterceptorOne") => NoClassDefFound

Next, I tried the following:

  @Override
  public AgentBuilder intercept(AgentBuilder agentBuilder) {
    ClassLoader cl = Thread.currentThread().getContextClassLoader();
    return agentBuilder
//      .type(isSubTypeOf(HandlerAdapter.class))
      .type(not(isInterface())
        .and(safeHasSuperType(named("org.springframework.web.servlet.HandlerAdapter"))))
      .transform((builder, typeDescription, classLoader, module) -> {
          try {
            Class<?> claz = Thread.currentThread().getContextClassLoader().loadClass("my.package.name.SpringBootInterceptorOne");
            return builder.visit(Advice.to(claz, claz,
              new ClassFileLocator.Compound(ClassFileLocator.ForClassLoader.of(cl),
              ClassFileLocator.ForClassLoader.of(Thread.currentThread().getContextClassLoader())
              )).on(named("handle").and(isMethod())));
          } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return builder;
          }
        }
      );
  }

This causes the interceptor to be "installed". The entry and exit methods are called okay. But casting the arguments to proper types gives error for the types of the arguments

exit spring boot
[Ljava.lang.Object;@c83066a
java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest
    at my.package.name.SpringBootInterceptorOne.getEndpoint(SpringBootInterceptorOne.java:36)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

Here is SpringBootInterceptorOne for reference:

  @Advice.OnMethodExit
  static void exit(@Advice.Origin final Executable executable,
                   @Advice.This Object handlerAdapter,
                   @Advice.AllArguments Object[] arguments,
                   @Advice.Enter final TimerContext ctx) {
//      final long duration = ctx.getDuration();
    System.out.println("exit spring boot");
    String e = getEndpoint(arguments);
    System.out.println(e);
  }

  public static String getEndpoint(Object[] arguments) {
    System.out.println(arguments);
    HttpServletRequest request = (HttpServletRequest) arguments[0];
    HandlerMethod  handler = (HandlerMethod) arguments[2];
    return "ad";
  }

UPDATE:

As per the advice offered in an answer, I tried the following:

  @Override
  public AgentBuilder intercept(AgentBuilder agentBuilder) {
    return agentBuilder
//      .type(isSubTypeOf(HandlerAdapter.class))
      .type(not(isInterface())
        .and(safeHasSuperType(named("org.springframework.web.servlet.HandlerAdapter"))))
      .transform(new AgentBuilder.Transformer.ForAdvice()
        .include(SpringBootInterceptorOne.class.getClassLoader())
        .include(getClass().getClassLoader())
        .advice(named("handle"), SpringBootInterceptorOne.class.getName())
      );
  }

It again throws Error:

java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest
    at io.signoz.interceptors.http.server.springboot.SpringBootInterceptorOne.getEndpoint(SpringBootInterceptorOne.java:37) ~[na:na]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar!/:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_242]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_242]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.30.jar!/:9.0.30]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_242]

回答1:

The problem is that the advice class will be loaded on the system class loader as a part of the agent whereas the actual application code is loaded on a sub-class loader that is not visible to the system class loader. This situation does not change if you load your agent on the boot loader either. Therefore, the agent cannot load the HttpServletRequest class which is part of the uber-jar.

This is a typical problem with agents and Byte Buddy has a standard way to circumvent it by using a Transformer.ForAdvice instance instead of using the Advice class directly. Byte Buddy then creates a virtual class loader hierarchy that considers classes represented by both class loaders.

Update: The problem is that you are calling down to your interceptor that is defined in the system class loader where the class in question is not available. The annotated code will be inlined but the invoked method will not. If you copy-pasted the code into the annotated method, the behavior is as you'd expect it. Byte Buddy uses the annotated code as template and reuses a lot of information emitted by javac to guarantee a speedy conversion. Therefore, the library cannot simply copy the method and should rather feed the entire method body to javac.

来源：https://stackoverflow.com/questions/60237664/classpath-problems-while-instrumenting-springboot-application

标签

java