java.lang.IllegalArgumentException: node to traverse cannot be null!	org.hibernate.hql.ast.util.NodeTraverser.traverseDepthFirst(NodeTraverser.java:55)	org.hibernate.hql.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:280)	org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:182)	org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)	org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101)	org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80)	org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:94)	org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156)	org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135)	org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1651)	org.springframework.orm.hibernate3.HibernateTemplate$29.doInHibernate(HibernateTemplate.java:842)	org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:372)	org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:840)	org.springframework.orm.hibernate3.HibernateTemplate.find(HibernateTemplate.java:836)	org.bookonline.dao.imp.BookDAO.getTotalByCatalog(BookDAO.java:37)	org.bookonline.service.imp.BookService.getTotalByCatalog(BookService.java:28)	org.bookonline.action.BookAction.browseBookPaging(BookAction.java:53)	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)	com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)	com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)	org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)	org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:192)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)	org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)	org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:510)	org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)	org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)

　　解决的办法：

　　引起此种问题的原因就是hql有问题。今天一不小心 就把 from 写成了 form 。才导致这个错误。

node to traverse cannot be null!