关于java.lang.ClassCastException: org.jbpm.jpdl.internal.model.JpdlProcessDefinition cannot be cast to java.util.List

      一时犯懒，在Jbpm4.1安装包中用了ant create.user.webapp来创建一个Web应用，其中的lib包内容如下：

但在进行流程定义查询时
如List<ProcessDefinition> processDefinitions = repositoryService.createProcessDefinitionQuery().orderAsc(ProcessDefinitionQuery.PROPERTY_NAME).list();
发生如下错误：
java.lang.ClassCastException: org.jbpm.jpdl.internal.model.JpdlProcessDefinition cannot be cast to java.util.List
org.jbpm.pvm.internal.repository.ProcessDeployer.deploy(ProcessDeployer.java:64)
org.jbpm.pvm.internal.repository.DeployerManager.deploy(DeployerManager.java:46)
org.jbpm.pvm.internal.repository.RepositorySessionImpl.getObject(RepositorySessionImpl.java:120)
org.jbpm.pvm.internal.query.ProcessDefinitionQueryImpl.execute(ProcessDefinitionQueryImpl.java:72)
org.jbpm.pvm.internal.query.AbstractQuery.execute(AbstractQuery.java:81)
org.jbpm.pvm.internal.svc.DefaultCommandService.execute(DefaultCommandService.java:42)
org.jbpm.pvm.internal.tx.jta.JtaTransactionInterceptor.executeInNewTx(JtaTransactionInterceptor.java:79)
org.jbpm.pvm.internal.tx.jta.JtaTransactionInterceptor.execute(JtaTransactionInterceptor.java:61)
org.jbpm.pvm.internal.svc.RetryInterceptor.execute(RetryInterceptor.java:55)
org.jbpm.pvm.internal.tx.jta.JtaRetryInterceptor.executeWithRetry(JtaRetryInterceptor.java:52)
org.jbpm.pvm.internal.tx.jta.JtaRetryInterceptor.execute(JtaRetryInterceptor.java:45)
org.jbpm.pvm.internal.svc.EnvironmentInterceptor.execute(EnvironmentInterceptor.java:46)
org.jbpm.pvm.internal.query.AbstractQuery.untypedList(AbstractQuery.java:62)
org.jbpm.pvm.internal.query.ProcessDefinitionQueryImpl.list(ProcessDefinitionQueryImpl.java:141)
org.jbpm.integration.console.ProcessManagementImpl.getProcessDefinitions(ProcessManagementImpl.java:61)
org.jboss.bpm.console.server.ProcessMgmtFacade.getDefinitionsJSON(ProcessMgmtFacade.java:107)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:117)
org.jboss.resteasy.core.ResourceMethod.invokeOnTarget(ResourceMethod.java:260)
org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:232)
org.jboss.resteasy.core.ResourceMethod.invoke(ResourceMethod.java:166)
org.jboss.resteasy.core.DispatcherUtilities.getJaxrsResponse(DispatcherUtilities.java:142)
org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:356)
org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:173)
org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:93)
org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:68)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.jboss.bpm.console.server.util.GWTJsonFilter.doFilter(GWTJsonFilter.java:59)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
一直找不到原因，最后的原因竟然又是jar包的问题，解决方法：
将WEB-INF\lib下的jar包全部删除，把Jbpm安装包的lib目录下的所有jar包都复制过来，当然别忘了复制上一级目录的jbpm.jar包，当然如果用的是tomcat6.0以上的话，记得把那三个jar包（参考JBPM4项目和tomcat6.0的兼容问题）删除了，不然又出错了。以后还是自己老老实实导入jar包了，不推荐用命令产生的Web应用（里面没啥东西，不如不用）