当我在IDE中使用URLClassLoader时，我没有问题。当我尝试将我的代码作为jar应用程序（java -jar myApp.jar）执行时，则类加载器无法正常工作。
详细地，当以jar执行并且仅当我使用自己的类作为参数时，只有getMethod（）方法无法正常工作。
URL url = DAPBPropertyBuilder.class.getProtectionDomain().getCodeSource().getLocation().toURI().toURL();
URLClassLoader cl = URLClassLoader.newInstance(new URL[]{url});
Class<?> c = cl.loadClass("my.path.to.class.Myclass);
Constructor constructor = c.getConstructor();
Object dapbBuilderInstance = constructor.newInstance();
Class[] cArg = new Class[4];
cArg[0] = java.lang.String.class;
cArg[1] = java.util.List.class;
//Here the curious part: When I add the MyDTO.class as parameter, it throws an java.lang.NoSuchMethodException. When I reduce this parameter, everything works fine (also when executing as JAR).
cArg[2] = MyDTO.class;
cArg[3] = java.util.Map.class;
//This is throwing an exception only when executed as JAR
java.lang.reflect.Method method = dapbBuilderInstance.getClass().getMethod("builder", cArg);
如上面的源代码中所述，我已经可以确定问题出在MyDTO.class参数上。当我减少“ builder”方法中的参数以使此类不再是参数时，它可以正常工作。
我试图找出可能不匹配的地方，并写了以下几行：
// Give me all methods you know.
Method[] m = dapbBuilderInstance.getClass().getMethods();
for(int i =0; i<m.length;i++){
System.out.println( "Found method: " +m[i].getName());
//Found parameter:
System.out.println("params: " + Arrays.toString( m[i].getParameterTypes()));
//Used parameter for getMethod():
System.out.println("params: " +Arrays.toString( cArg ));
}
这里输出：
MethodName: builder
param: [class java.lang.String, interface java.util.List, class my.path.to.class.MyDTO, interface java.util.Map]
param: [class java.lang.String, interface java.util.List, class my.path.to.class.MyDTO, interface java.util.Map]
因此，应该没问题，但仍然出现异常：
java.lang.NoSuchMethodException: my.path.to.class.MyClass.builder(java.lang.String, java.util.List, my.path.to.class.MyDTO, java.util.Map)
at java.lang.Class.getMethod(Unknown Source)
...
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at javax.el.BeanELResolver.invoke(BeanELResolver.java:158)
at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:79)
at org.apache.el.parser.AstValue.getValue(AstValue.java:159)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:190)
at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:115)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:200)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:187)
at javax.faces.component.UIOutput.getValue(UIOutput.java:179)
at javax.faces.component.UIInput.getValue(UIInput.java:311)
at org.primefaces.util.ComponentUtils.getValueToRender(ComponentUtils.java:97)
at org.primefaces.util.ComponentUtils.getValueToRender(ComponentUtils.java:61)
at org.primefaces.extensions.component.codemirror.CodeMirrorRenderer.encodeMarkup(CodeMirrorRenderer.java:103)
at org.primefaces.extensions.component.codemirror.CodeMirrorRenderer.encodeEnd(CodeMirrorRenderer.java:87)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:949)
at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:91)
at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:73)
at org.primefaces.component.dialog.DialogRenderer.encodeContent(DialogRenderer.java:192)
at org.primefaces.component.dialog.DialogRenderer.encodeMarkup(DialogRenderer.java:116)
at org.primefaces.component.dialog.DialogRenderer.encodeEnd(DialogRenderer.java:48)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:949)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1912)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:918)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1905)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1908)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1908)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:491)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:194)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:126)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:223)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
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.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManagerInViewFilter.java:185)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.servlet.resource.ResourceUrlEncodingFilter.doFilter(ResourceUrlEncodingFilter.java:63)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:119)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:74)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270)
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:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
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:92)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
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.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
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:200)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
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:200)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
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:408)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
[也许您有一个想法，当我将MyDTO类作为java -jar MyApp.jar执行时，将MyDTO类用作“ builder”方法的参数时，为什么Java无法找到该方法。
我有点没主意了。
谢谢！
约翰内斯得到了答案。
cArg[2] = cl.loadClass(DataSourceDescription.class.getName());
解决了问题。