Cannot resolve type description for [class of jdk]

[zhanjinhao]

Hello.

I have two agents.

One will isolate log4j2 by custom classloader which load class from specific directory instead of appclassloader, and the other will check whether the class's parents is target type.

the parent classloader of custom classloader is appclassloader.

the second agent's code that check the type of class's parent is below:

  @Override
  public boolean isMatch(TypeDescription typeDescription) {
    List<String> tmpList = new ArrayList<>(Arrays.asList(this.parentTypes));

    TypeList.Generic implInterfaces = typeDescription.getInterfaces();
    for (TypeDescription.Generic implInterface : implInterfaces) {
      matchHierarchyClass(implInterface, tmpList);
    }

    if (typeDescription.getSuperClass() != null) {
      matchHierarchyClass(typeDescription.getSuperClass(), tmpList);
    }

    return tmpList.isEmpty();
  }

  private void matchHierarchyClass(TypeDescription.Generic clazz, List<String> parentTypes) {
    parentTypes.remove(clazz.asRawType().getTypeName());
    if (parentTypes.isEmpty()) {
      return;
    }

    for (TypeDescription.Generic generic : clazz.getInterfaces()) {
      matchHierarchyClass(generic, parentTypes);
    }

    TypeDescription.Generic superClazz = clazz.getSuperClass();
    if (superClazz != null && !clazz.getTypeName().equals("java.lang.Object")) {
      matchHierarchyClass(superClazz, parentTypes);
    }

  }

when i run springboot with the two agents:

-javaagent:C:\workspace\project\incubating\port-trail\dist\porttrail-agent.jar
-javaagent:C:\workspace\learn\skywalking-agent-learn\dist\apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar

error will output:

2026-01-08 22:11:40.426 [main] WARN  [cn.addenda.porttrail.agent.transform.match.ProtectiveShieldMatcher.matches.33] - Byte-buddy occurs exception when match type [class org.apache.logging.log4j.spi.AbstractLogger].
cn.addenda.porttrail.dependency.net.bytebuddy.pool.TypePool$Resolution$NoSuchTypeException: Cannot resolve type description for java.io.Serializable
	at cn.addenda.porttrail.dependency.net.bytebuddy.pool.TypePool$Resolution$Illegal.resolve(TypePool.java:192) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.pool.TypePool$Default$WithLazyResolution$LazyTypeDescription.delegate(TypePool.java:1170) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.description.type.TypeDescription$AbstractBase$OfSimpleType$WithDelegation.getInterfaces(TypeDescription.java:8451) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.description.type.TypeDescription$Generic$OfNonGenericType.getInterfaces(TypeDescription.java:3698) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.matcher.HasSuperTypeMatcher.doMatch(HasSuperTypeMatcher.java:67) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.matcher.HasSuperTypeMatcher.doMatch(HasSuperTypeMatcher.java:32) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.matcher.ElementMatcher$Junction$ForNonNullValues.matches(ElementMatcher.java:249) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.matcher.ElementMatcher$Junction$Conjunction.matches(ElementMatcher.java:146) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.matcher.ElementMatcher$Junction$Disjunction.matches(ElementMatcher.java:214) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.agent.transform.match.ProtectiveShieldMatcher.matches(ProtectiveShieldMatcher.java:31) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$RawMatcher$ForElementMatchers.matches(AgentBuilder.java:1968) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doTransform(AgentBuilder.java:12703) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:12661) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.access$1800(AgentBuilder.java:12370) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:13070) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer$LegacyVmDispatcher.run(AgentBuilder.java:13008) ~[porttrail-agent.jar:?]
	at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_221]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.doPrivileged(AgentBuilder.java) ~[porttrail-agent.jar:?]
	at cn.addenda.porttrail.dependency.net.bytebuddy.agent.builder.AgentBuilder$Default$ExecutingTransformer.transform(AgentBuilder.java:12570) ~[porttrail-agent.jar:?]
	at sun.instrument.TransformerManager.transform(TransformerManager.java:188) ~[?:1.8.0_221]
	at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:428) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass(ClassLoader.java:642) ~[?:1.8.0_221]
	at cn.addenda.sal.agent.core.log.LogClassLoader.doFindClass(LogClassLoader.java:99) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at cn.addenda.sal.agent.core.log.LogClassLoader.loadClass(LogClassLoader.java:69) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass1(Native Method) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[?:1.8.0_221]
	at java.lang.ClassLoader.defineClass(ClassLoader.java:642) ~[?:1.8.0_221]
	at cn.addenda.sal.agent.core.log.LogClassLoader.doFindClass(LogClassLoader.java:99) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at cn.addenda.sal.agent.core.log.LogClassLoader.loadClass(LogClassLoader.java:69) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_221]
	at org.apache.logging.log4j.LogManager.<clinit>(LogManager.java:61) ~[log4j-api-2.17.2.jar:2.17.2]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_221]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_221]
	at cn.addenda.sal.agent.core.log.MyLoggerFactory.<clinit>(MyLoggerFactory.java:35) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at cn.addenda.sal.agent.SkywalkingLearnAgent.<clinit>(SkywalkingLearnAgent.java:36) ~[apm-agent-1.0-SNAPSHOT-jar-with-dependencies.jar:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_221]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_221]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_221]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_221]
	at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:386) ~[?:1.8.0_221]
	at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:401) ~[?:1.8.0_221]

I have searched the issue of bytebuddy and I know bytebuddy will analyze bytecode of class, so if there is not bytecode exists, bytebuddy can not get type.

but , my problem is : the type which can not be resolved is jdk's class.

All the class which match failed are class that loading from my custom classloader.

can somebody give me some advise. thanks!

[raphw]

How did you resolve your AgentBuilder?

[zhanjinhao]

@raphw

my first agent's AgentBuilder is :

  public static void premain(String args, Instrumentation instrumentation) {


    log.info("进入到premain, SkywalkingLearnAgent.class.classLoader = {}, args:{}",
            SkywalkingLearnAgent.class.getClassLoader(), args);


    log2.info("进入到premain, SkywalkingLearnAgent.class.classLoader = {}, args:{}",
            SkywalkingLearnAgent.class.getClassLoader(), args);

    PluginFinder pluginFinder;
    try {
      pluginFinder = new PluginFinder(new PluginBootstrap().loadPlugin());
    } catch (Exception e) {
      log.error("初始化失败", e);
      return;
    }

    ByteBuddy byteBuddy = new ByteBuddy().with(TypeValidation.of(true));

    AgentBuilder with = new AgentBuilder.Default(byteBuddy)
            .ignore(
                    nameStartsWith("net.bytebuddy.")
                            .or(nameStartsWith("org.springframework."))
                            .or(nameStartsWith("org.slf4j."))
                            .or(nameStartsWith("org.groovy."))
                            .or(nameContains("javassist"))
                            .or(nameContains(".asm."))
                            .or(nameContains(".reflectasm."))
                            .or(nameStartsWith("sun.reflect"))
                            .or(ElementMatchers.isSynthetic()))
            // 当要被拦截的type第一次要被加载的时候会进入这里
            .type(pluginFinder.buildMatch())
            .transform(new AgentTransformer(pluginFinder))
            .with(new Listener());

    with.installOn(instrumentation);
  }

and my custom classloader is :

package cn.addenda.sal.agent.core.log;

import cn.addenda.sal.agent.core.boot.AgentPackagePath;
import cn.addenda.sal.agent.core.plugin.PluginBootstrap;
import lombok.Getter;
import org.apache.commons.io.IOUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * 用于加载插件和插件的拦截器
 */
public class LogClassLoader extends ClassLoader {

  /**
   * 用于加载日志组件的加载器
   */
  @Getter
  private static LogClassLoader DEFAULT_LOADER;

  /**
   * 自定义类加载器加载类的路径
   */
  private List<File> classpath;
  private List<Jar> allJarList;

  public LogClassLoader(ClassLoader parent) {
    super(parent);

    File agentJarDir = AgentPackagePath.getPath();
    System.out.println(String.format("logLibDir: %s", agentJarDir));

    classpath = new ArrayList<>();
    allJarList = doGetJars();

    classpath.add(new File(new File(agentJarDir.getParent(), "lib"), "log"));
  }

  private static List<String> logPrefixList = new ArrayList<>();

  static {
    logPrefixList.add("org.slf4j.");
    logPrefixList.add("org.apache.logging.log4j.");
    logPrefixList.add("org.apache.logging.slf4j.");
  }

  @Override
  public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
    Class<?> loadedClass = findLoadedClass(name);
    if (loadedClass != null) {
      for (String logPrefix : logPrefixList) {
        if (name.startsWith(logPrefix)) {
          System.out.println("findLoadedClass : " + name);
        }
      }
      return loadedClass;
    }

    for (String logPrefix : logPrefixList) {
      if (name.startsWith(logPrefix)) {
        Class<?> aClass = doFindClass(name);
        if (resolve) {
          resolveClass(aClass);
        }
      }
    }

    return super.loadClass(name, resolve);
  }

  /**
   * loadClass --> findClass（自定义自己的类加载逻辑） --> defineClass
   */
  @Override
  protected Class<?> findClass(String name) throws ClassNotFoundException {
    return super.findClass(name);
  }

  private Class<?> doFindClass(String name) throws ClassNotFoundException {
    List<Jar> _allJarList = allJarList;

    String concat = name.replace(".", "/").concat(".class");
    for (Jar jar : _allJarList) {
      JarEntry jarEntry = jar.jarFile.getJarEntry(concat);
      if (jarEntry == null) {
        continue;
      }
      try {
        URL url = new URL("jar:file:" + jar.sourceFile.getAbsolutePath() + "!/" + concat);
        byte[] byteArray = IOUtils.toByteArray(url);
        return defineClass(name, byteArray, 0, byteArray.length);
      } catch (Exception e) {
        System.out.println(String.format("find class %s error", name));
      }
    }
    throw new ClassNotFoundException("can not find " + name);
  }

  private List<Jar> doGetJars() {
    List<Jar> _allJarList = new ArrayList<>();
    File agentJarDir = AgentPackagePath.getPath().getParentFile();
    System.out.println("Agent base directory: " + agentJarDir);
    File logLibDir = new File(new File(agentJarDir, "lib"), "log");

    if (logLibDir.exists() && logLibDir.isDirectory()) {
      String[] list = logLibDir.list((dir, name) -> name.endsWith(".jar"));
      if (list == null || list.length == 0) {
        return _allJarList;
      }
      for (String s : list) {
        File jarSourceFile = new File(logLibDir, s);
        try {
          Jar jar = new Jar(new JarFile(jarSourceFile), jarSourceFile);
          _allJarList.add(jar);
          System.out.println(String.format("load jar %s success.", jarSourceFile));
        } catch (Exception e) {
          System.out.println(String.format("jar %s load fail.", jarSourceFile));
          e.printStackTrace();
        }
      }
    }
    return _allJarList;
  }

  private static class Jar {
    /**
     * jar文件对对应的jarFile对象
     */
    private final JarFile jarFile;
    /**
     * jar文件
     */
    private final File sourceFile;

    public Jar(JarFile jarFile, File sourceFile) {
      this.jarFile = jarFile;
      this.sourceFile = sourceFile;
    }
  }

  @Override
  public Enumeration<URL> getResources(String name) throws IOException {
    List<URL> allResources = new ArrayList<>();
    for (Jar jar : allJarList) {
      JarEntry jarEntry = jar.jarFile.getJarEntry(name);
      if (jarEntry == null) {
        continue;
      }
      try {
        URL url = new URL("jar:file:" + jar.sourceFile.getAbsolutePath() + "!/" + name);
        allResources.add(url);
      } catch (Exception e) {
        System.out.println(String.format("find file {} error", name));
        e.printStackTrace();
      }
    }
    Iterator<URL> iterator = allResources.iterator();
    return new Enumeration<URL>() {
      @Override
      public boolean hasMoreElements() {
        return iterator.hasNext();
      }

      @Override
      public URL nextElement() {
        return iterator.next();
      }
    };
  }

  @Override
  public URL getResource(String name) {
    // todo 设置为线程上下文类加载器，再从这里读取外部目录的log4j2.xml
    for (Jar jar : allJarList) {
      JarEntry jarEntry = jar.jarFile.getJarEntry(name);
      if (jarEntry == null) {
        continue;
      }
      try {
        // 返回第一个
        URL url = new URL("jar:file:" + jar.sourceFile.getAbsolutePath() + "!/" + name);
        return url;
      } catch (Exception e) {
        System.out.println(String.format("find file {} error", name));
        e.printStackTrace();
      }
    }
    return null;
  }

  public static void initDefaultLoader() {
    if (DEFAULT_LOADER == null) {
      DEFAULT_LOADER = new LogClassLoader(PluginBootstrap.class.getClassLoader());
    }
  }

}

my second agent's AgentBuilder is :

  public static void premain(String args, Instrumentation instrumentation) {

    addBootLibToBootstrapClassLoaderSearch(instrumentation);

    PortTrailLogger log = AgentPortTrailLoggerFactory.getInstance().getPortTrailLogger(PortTrailAgent.class);

    log.info("{} start enhancement, and classLoader = {}, args:{}",
            PortTrailAgent.class, PortTrailAgent.class.getClassLoader(), args);

    InterceptorPointDefineGather interceptorPointDefineGather = getInterceptorGather();

    ByteBuddy byteBuddy = new ByteBuddy().with(TypeValidation.of(true));

    AgentBuilder with = new AgentBuilder.Default(byteBuddy)
            .with(new AgentBuilder.PoolStrategy() {
              @Override
              public TypePool typePool(ClassFileLocator classFileLocator, ClassLoader classLoader) {
                File bootDir = new File(AgentPackage.getPath(), "boot");
                File linkDir = new File(AgentPackage.getPath(), "link");

                // 收集所有JAR文件
                List<File> bootJars = searchJars(bootDir);
                List<File> linkJars = searchJars(linkDir);

                // 创建复合ClassFileLocator
                List<ClassFileLocator> locators = new java.util.ArrayList<>();
                locators.add(classFileLocator);

                for (File jar : bootJars) {
                  try {
                    locators.add(ClassFileLocator.ForJarFile.of(jar));
                  } catch (IOException e) {
                    log.error("Cannot create ClassFileLocator for jar: {}", jar.getAbsolutePath(), e);
                  }
                }

                for (File jar : linkJars) {
                  try {
                    locators.add(ClassFileLocator.ForJarFile.of(jar));
                  } catch (IOException e) {
                    log.error("Cannot create ClassFileLocator for jar: {}", jar.getAbsolutePath(), e);
                  }
                }

                return TypePool.Default.WithLazyResolution.of(
                        new ClassFileLocator.Compound(locators.toArray(new ClassFileLocator[0]))
                );
              }

              @Override
              public TypePool typePool(ClassFileLocator classFileLocator, ClassLoader classLoader, String name) {
                return typePool(classFileLocator, classLoader);
              }
            })
            .ignore(
                    nameStartsWith("net.bytebuddy.")
                            .or(nameStartsWith("org.springframework.")
//                                    .and(ElementMatchers.not(ElementMatchers.named(SERVER_PROPERTIES_SERVLET_NAME)))
                            )
                            .or(nameStartsWith("org.slf4j."))
                            .or(nameStartsWith("org.groovy."))
                            .or(nameContains("javassist"))
                            .or(nameContains(".asm."))
                            .or(nameContains(".reflectasm."))
                            .or(nameStartsWith("sun.reflect"))
                            .or(ElementMatchers.isSynthetic())
            )
            // 当要被拦截的type第一次要被加载的时候会进入这里
            .type(interceptorPointDefineGather.buildMatch())
            .transform(new AgentTransformer(interceptorPointDefineGather))
            .with(new AgentListener());

    with.installOn(instrumentation);
  }

In my second AgentBuilder, I customize a type pool because I add some jars to BootstrapClassLoaderSearch.

All the exception that "Cannot resolve type description " occurs when my custom classloader of first agent load log4j and slf4j from external jars.