我正在编写一个Jsp页面,该页面使用scriptlet从控制器调用方法,该控制器使用DAO的方法,该方法执行存储在与该DAO相对应的模型中的命名查询.我希望此控制器方法返回一个Array@R_419_6818@,我可以对其进行迭代以检索其值以显示在页面上.
当Jsp进入方法调用时,它在控制器方法处给了我一个NPE,特别是在调用查询方法的那一行上.更令人烦恼的是,我在页面的前面调用了类似的方法,并且在那里没有异常.我的小组一直在使用带有Hibernate的Spring MVC框架来处理我们的映射.
我试图删除代码中不必要的部分,同时保留可能指向解决方案的内容.如果您需要更多信息,请告诉我,我们会尽快进行更新.
(我打算将来避免使用scriptlet,因为到目前为止我读过的所有问题都告诉我避免使用它们.)
这是代码：
ReportingController方法：
public Array@R_419_6818@<String> weekWorkPrints(User user,CurrentWeek week) { Array@R_419_6818@<UserTime> time@R_419_6818@ = userTimeDao .getPunchesForUserAscendingByTime(user); Array@R_419_6818@<String> prints = new Array@R_419_6818@<String>(); prints.add(utc.convertPeriodtoprint(utc.timeWorkedForADay( week.getSunday(),time@R_419_6818@))); return prints;}UserTimeDao方法调用查询：
@SuppressWarnings("unchecked")@Transactionalpublic Array@R_419_6818@<UserTime> getPunchesForUserAscendingByTime(User passedUser) { query loginquery = em .createnamedquery("fetchAllUserTimesForUserAscend"); loginquery.setParameter("user",passedUser); return (Array@R_419_6818@<UserTime>) loginquery.getResult@R_419_6818@();}UserTime模型中的命名查询：
@namedQuerIEs({ @namedquery(name = "fetchAllUserTimes",query = "SELECT ut FROM UserTime ut"),@namedquery(name = "fetchAllUserTimesForUserDesc",query = "SELECT ut FROM UserTime ut WHERE ut.user = :user ORDER BY ut.userClockIn DESC"),@namedquery(name = "fetchAllUserTimesForUserAscend",query = "SELECT ut FROM UserTime ut WHERE ut.user = :user ORDER BY ut.userClockIn")})JsP：
<%@ taglib uri="http://java.sun.com/Jsp/Jstl/core" prefix="c"%><%@page import="models.*"%><%@ page language="java" ContentType="text/HTML; charset=ISO-8859-1"pageEnCoding="ISO-8859-1"%><%@page import="models.*"%><%@page import="java.util.Array@R_419_6818@"%><%@page import="controllers.ReportingController"%><!DOCTYPE HTML PUBliC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/HTML4/loose.dtd"><Jsp:useBean ID="userDao" scope="request" /><Jsp:useBean ID="reportControl" scope="request" /><Jsp:useBean ID="currentWeekControl" scope="session" /><Jsp:useBean ID="userTimeDao" scope="request" /><HTML><head><link rel="stylesheet" type="text/CSS" href="CSS/global.CSS" /><link rel="stylesheet" type="text/CSS" href="CSS/reporting.CSS" /><Meta http-equiv="Content-Type" content="text/HTML; charset=ISO-8859-1"><Title>administrator - Reporting</Title></head><body><div ID="wrapper"> <div ID="header"> <h1>administrator Home</h1> <% User loginUser = (User) session.getAttribute("loginUser"); %> <p> Welcome,<%=loginUser.getUsername()%>! </p> </div><!-- ---- --> <table ID="loggedTimetable"> <% CurrentWeek currentWeek = (CurrentWeek) session .getAttribute("currentWeek"); %> <!-- --- --> <% for (User iteratedUser : userDao.getAlphabeticalUsers()) { Array@R_419_6818@<String> weekPrintouts = reportControl.weekWorkPrints( iteratedUser,currentWeek); %> <tr> <td><%=iteratedUser.getLastname()%>,<%=iteratedUser.getFirstname()%> </td> <td><%=weekPrintouts.get(0)%></td> </tr> <% } %> </table>空指针异常：
2012-08-19 21:21:02.315::WARN: nested in org.apache.jasper.JasperException: java.lang.NullPointerException: java.lang.NullPointerException at controllers.ReportingController.weekWorkPrints(ReportingController.java:106) at org.apache.Jsp.Jsp_002dpages.Reporting_Jsp._JspService(org.apache.Jsp.Jsp_002dpages.Reporting_Jsp:196) at org.apache.jasper.runtime.httpJspBase.service(httpJspBase.java:93) at javax.servlet.http.httpServlet.service(httpServlet.java:820) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373) at org.apache.jasper.servlet.JspServlet.serviceJspfile(JspServlet.java:470) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:364) at javax.servlet.http.httpServlet.service(httpServlet.java:820) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at org.mortbay.jetty.servlet.dispatcher.forward(dispatcher.java:285) at org.mortbay.jetty.servlet.dispatcher.forward(dispatcher.java:126) at org.springframework.web.servlet.vIEw.InternalResourceVIEw.renderMergedOutputModel(InternalResourceVIEw.java:238) at org.springframework.web.servlet.vIEw.AbstractVIEw.render(AbstractVIEw.java:250) at org.springframework.web.servlet.dispatcherServlet.render(dispatcherServlet.java:1047) at org.springframework.web.servlet.dispatcherServlet.dodispatch(dispatcherServlet.java:817) at org.springframework.web.servlet.dispatcherServlet.doService(dispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549) at javax.servlet.http.httpServlet.service(httpServlet.java:707) at javax.servlet.http.httpServlet.service(httpServlet.java:820) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:322) at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:116) at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.servletAPI.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:182) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.authentication.logout.logoutFilter.doFilter(logoutFilter.java:105) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87) at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:184) at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:155) at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237) at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:206) at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.httpconnection.handleRequest(httpconnection.java:505) at org.mortbay.jetty.httpconnection$RequestHandler.headerComplete(httpconnection.java:829) at org.mortbay.jetty.httpParser.parseNext(httpParser.java:514) at org.mortbay.jetty.httpParser.parseAvailable(httpParser.java:211) at org.mortbay.jetty.httpconnection.handle(httpconnection.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)您试图做的事情在Spring MVC中根本行不通,也不应该. MVC的目的是将模型,视图和控制器分开,但是您试图在视图内部创建控制器的实例.
相反,您拥有的返回JsP名称的控制器方法应首先调用您的weekWorkPrints方法,并将返回的@R_419_6818@放入Model中,以便JsP可以对其进行迭代.
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