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Java getMethod“找不到类”

[英]Java getMethod “class not found”

 原文  2014-10-21 15:16:16  5   3    java/ reflection/ classloader/ classnotfoundexception

问题描述

我有一个需要动态加载某些适配器的应用程序。 其中一些适配器被编译到应用程序中，而一些适配器在运行时提供。 一旦我有一个适配器，我想在其上调用adapt（OrderToolRequest，Object）方法。

我的问题是，当类在应用程序中时，我可以使它工作。 但是，对于第三方适配器，我可以动态加载运行时提供的类，但我无法弄清楚如何调用该方法。 我在OrderToolResponse上遇到“class not found”错误。 我试图通过让所有适配器实现接口和转换，并通过简单地使用反射来获取方法。

我假设这与不同的类加载器有某种关系，但我不足以解决问题。 谁能指出我正确的方向？

在下面的代码中，一切正常，直到调用getMethod（）。 如果我们在应用程序中找到该类，则会成功。 如果URLClassLoader加载了类，则抛出一个类错误 

Class<?> cls = null;

try
{
    // #1
    cls = Class.forName( adapterName );
}
catch ( ClassNotFoundException e )
{
    File file = new File( "Adapters" );
    URL url = file.toURI().toURL();
    URL[] urls = new URL[]{ url };

    URLClassLoader loader = new URLClassLoader( urls );
    try
    {
        // #2
        cls = loader.loadClass( adapterName );
    }
    finally 
    {
        loader.close();
    }
}

Constructor<?> constructor = cls.getConstructor();
Object instance = constructor.newInstance();

// #3 THE PROBLEM OCCURS HERE.  SUCCEEDS IF LOADED BY #1, BUT FAILS IF LOADED
// BY #2.
Method adaptMethod = cls.getMethod( "adapt", OrderToolRequest.class, Object.class );

...invoke the method, etc.

编辑更充分地解释

如果类由语句Class.forName（adapterName）加载，那么没有问题。

如果该类由loader.loadClass（adapterName）加载，则存在问题。

如果我改变代码阅读： 

Method adaptMethod = null;
try
{
    adaptMethod = cls.getMethod( "adapt", OrderToolRequest.class, Object.class );
}
catch ( Error e )
{
    log.error( "Didn't work" );
}

并在日志记录语句中设置断点，然后：

  • e.cause =“ClassNotFoundException”
  • e.detailMessage =“com / ca /​​ eai / model / canonical / OrderToolResponse”

编辑＃2堆栈跟踪。 我不得不截断超过30,000个字符

您将看到由ClassNotFoundException引起的NoClassDefFoundError。 

java.lang.NoClassDefFoundError: com/ca/eai/model/canonical/OrderToolResponse
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2442)
    at java.lang.Class.getMethod0(Class.java:2685)
    at java.lang.Class.getMethod(Class.java:1620)
    at com.ca.eai.esb.transformer.orchestration.AdapterInvokingTransformer.findAdapter(AdapterInvokingTransformer.java:73)
    at com.ca.eai.esb.transformer.orchestration.AdapterInvokingTransformer.transformMessage(AdapterInvokingTransformer.java:106)
    at org.mule.transformer.AbstractMessageTransformer.transform(AbstractMessageTransformer.java:145)
    at org.mule.transformer.AbstractMessageTransformer.transform(AbstractMessageTransformer.java:93)
    at org.mule.DefaultMuleMessage.transformMessage(DefaultMuleMessage.java:1455)
    at org.mule.DefaultMuleMessage.applyAllTransformers(DefaultMuleMessage.java:1363)
    at org.mule.DefaultMuleMessage.applyTransformers(DefaultMuleMessage.java:1341)
    at org.mule.DefaultMuleMessage.applyTransformers(DefaultMuleMessage.java:1333)
    at org.mule.transformer.AbstractTransformer.process(AbstractTransformer.java:123)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:95)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:54)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:26)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:70)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:65)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:95)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:54)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:26)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:70)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:65)
    at org.mule.routing.AbstractSelectiveRouter.processEventWithProcessor(AbstractSelectiveRouter.java:312)
    at org.mule.routing.AbstractSelectiveRouter.routeWithProcessors(AbstractSelectiveRouter.java:302)
    at org.mule.routing.AbstractSelectiveRouter.process(AbstractSelectiveRouter.java:202)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:95)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:106)
    at org.mule.interceptor.AbstractEnvelopeInterceptor.process(AbstractEnvelopeInterceptor.java:55)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:106)
    at org.mule.processor.AsyncInterceptingMessageProcessor.process(AsyncInterceptingMessageProcessor.java:101)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:95)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:106)
    at org.mule.interceptor.AbstractEnvelopeInterceptor.process(AbstractEnvelopeInterceptor.java:55)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:106)
    at org.mule.processor.AbstractFilteringMessageProcessor.process(AbstractFilteringMessageProcessor.java:44)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.AbstractInterceptingMessageProcessorBase.processNext(AbstractInterceptingMessageProcessorBase.java:106)
    at org.mule.construct.AbstractPipeline$1.process(AbstractPipeline.java:112)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:95)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:54)
    at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:70)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.access$001(InterceptingChainLifecycleWrapper.java:26)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper$1.process(InterceptingChainLifecycleWrapper.java:70)
    at org.mule.execution.ExceptionToMessagingExceptionExecutionInterceptor.execute(ExceptionToMessagingExceptionExecutionInterceptor.java:27)
    at org.mule.execution.MessageProcessorNotificationExecutionInterceptor.execute(MessageProcessorNotificationExecutionInterceptor.java:61)
    at org.mule.execution.MessageProcessorExecutionTemplate.execute(MessageProcessorExecutionTemplate.java:47)
    at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:65)
    at org.mule.construct.Flow$1.process(Flow.java:74)
    at org.mule.construct.Flow$1.process(Flow.java:69)
    at org.mule.execution.ExecuteCallbackInterceptor.execute(ExecuteCallbackInterceptor.java:20)
    at org.mule.execution.HandleExceptionInterceptor.execute(HandleExceptionInterceptor.java:34)
    at org.mule.execution.HandleExceptionInterceptor.execute(HandleExceptionInterceptor.java:18)
    at org.mule.execution.BeginAndResolveTransactionInterceptor.execute(BeginAndResolveTransactionInterceptor.java:58)
    at org.mule.execution.SuspendXaTransactionInterceptor.execute(SuspendXaTransactionInterceptor.java:54)
    at org.mule.execution.RethrowExceptionInterceptor.execute(RethrowExceptionInterceptor.java:32)
    at org.mule.execution.RethrowExceptionInterceptor.execute(RethrowExceptionInterceptor.java:17)
    at org.mule.execution.ErrorHandlingExecutionTemplate.execute(ErrorHandlingExecutionTemplate.java:63)
    at org.mule.execution.ErrorHandlingExecutionTemplate.execute(ErrorHandlingExecutionTemplate.java:34)
    at org.mule.construct.Flow.process(Flow.java:68)
...SOME STUFF REMOVED HERE...
Caused by: java.lang.ClassNotFoundException: com.ca.eai.model.canonical.OrderToolResponse
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    ... 260 more

3 个解决方案

解决方案1
 1  2014-10-21 15:27:31

不要关闭装载机。 的Javadoc：

关闭此URLClassLoader，以便它不再可用于加载此加载程序定义的新类或资源。

解决方案2
 0  2014-10-21 16:36:52

如果没有看到我们尝试检索的类或方法，但是看看你提供的异常，我不相信Class＃getMethod会抛出ClassNotFoundException。

相反，目标方法“adapt”可能具有com.ca.eai.model.canonical.OrderToolResponse的返回类型，并且该类不在Classpath中。

解决方案3
 0  2014-10-21 17:07:04

构建URL加载器如下解决了我的问题。 

URLClassLoader loader = new URLClassLoader( urls, OrderToolResponse.class.getClassLoader() );

我仍然不确定为什么默认的类加载器不起作用。

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