Java getMethod“；“未找到类”；

我有一个应用程序需要动态加载一些适配器。其中一些适配器被编译到应用程序中，而另一些则在运行时提供。一旦有了适配器，我就要调用适配器上的adapt（OrderToolRequest，Object）方法

我的问题是，当类在应用程序中时，我可以让它工作。但是，对于第三方适配器，我可以动态加载运行时提供的类，但我不知道如何调用该方法。我在OrderToolResponse上收到“未找到类”错误。我试图通过让所有适配器实现接口和强制转换，并通过简单地使用反射来获得方法来实现这一点

我假设这与不同的类装入器有关，但我的知识还不足以解决这个问题。谁能给我指出正确的方向吗

在下面的代码中，在调用getMethod（）之前，一切正常。如果我们在应用程序中找到该类，则会成功。如果该类是由URLClassLoader加载的，则会抛出“找不到类”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.

并在日志语句上设置断点，然后：

• e、 原因=“ClassNotFoundException”
• e、 详细信息= “com/ca/eai/model/canonical/OrderToolResponse”

编辑#2堆栈跟踪。我不得不截断30000多个字符

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

---

请勿关闭装载机。Javadoc：

关闭此URLClassLoader，使其不再用于加载 此加载程序定义的新类或资源

---

没有看到我们试图检索的类或方法，但是查看您提供的异常原因，我认为不会抛出ClassNotFoundException

---

相反，目标方法“adapt”的返回类型可能为com.ca.eai.model.canonical.OrderToolResponse，而该类不在类路径中

如下构造URL加载器解决了我的问题

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

---

我仍然不确定默认类加载器为什么不工作。

编译器如何知道OrderToolRequest是什么？它在生成文件中吗？它在通过Maven依赖项引入的类路径中的一个jar中。如何抛出类未找到异常？@A4L:如果找不到参数类型。@Ali C:注意，我没有说它在抛出异常；我说这是个错误。尽管如此，我还是编辑了文章以包含堆栈跟踪。

URLClassLoader=newurlclassloader（url，ClassLoader.getSystemClassLoader（））将是我的下一个想法。不仅为cls类提供URLClassLoader，还提供系统类装入器。或者
getClass.getClassLoader（）
。然而，这种想法确实让我找到了一个解决方法。更改为URLClassLoader=newURLClassLoader（URL，OrderToolResponse.class.getClassLoader（））；这个类和OrderToolRequest在同一个jar中。我可以在这个函数的代码中插入一行“OrderToolResponse=new OrderToolResponse（）；”，它工作得非常好。这与URLClassLoader在其路径中没有jar这一事实有关吗？尝试一下并没有什么坏处，但是按照您定义它的方式，URLClassLoader应该委托给默认的类加载器，这样就可以在类路径中找到东西。如果您使用新的URLClassLoader（URL，null）实例化URLClassLoader，它将不会委托，那么我会期望出现这种行为……URLClassLoader=newURLClassLoader（URL，OrderToolResponse.class.getClassLoader（））；工作。
URLClassLoader loader = new URLClassLoader( urls, OrderToolResponse.class.getClassLoader() );