java - Spring MVC + Hibernate + JSP

Question

我是这些工具的新手，所以您可能会觉得这很愚蠢。

我在尝试访问我的网络应用程序时遇到此错误(我应该在其中显示数据库“用户”表中的每个用户。

HTTP ERROR 500

Problem accessing /maven-archetype-webapp/index. Reason:

    Neither BindingResult nor plain target object for bean name 'contact' available as request attribute
Caused by:

java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'contact' available as request attribute
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:141)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188)
    at org.springframework.web.servlet.tags.form.LabelTag.autogenerateFor(LabelTag.java:130)
    at org.springframework.web.servlet.tags.form.LabelTag.resolveFor(LabelTag.java:120)
    at org.springframework.web.servlet.tags.form.LabelTag.writeTagContent(LabelTag.java:90)
    at org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84)
    at org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80)
    at org.apache.jsp.WEB_002dINF.jsp.usuario_jsp._jspx_meth_form_label_0(org.apache.jsp.WEB_002dINF.jsp.usuario_jsp:299)
    at org.apache.jsp.WEB_002dINF.jsp.usuario_jsp._jspx_meth_form_form_1(org.apache.jsp.WEB_002dINF.jsp.usuario_jsp:222)
    at org.apache.jsp.WEB_002dINF.jsp.usuario_jsp._jspService(org.apache.jsp.WEB_002dINF.jsp.usuario_jsp:106)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:389)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:486)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:380)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
    at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:327)
    at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)
    at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:209)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:266)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1225)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1012)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
    at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
    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:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

所以我要向您发送我的 Controller 、我的 JSP 和我的服务实现。

UsuarioController.java

package org.maven.archetypes.Project.controller;


import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.maven.archetypes.Project.form.Usuario;
import org.maven.archetypes.Project.service.UsuarioService;


@Controller
public class UsuarioController {

    @Autowired
     private UsuarioService usuarioService;
    @RequestMapping("/index")
     public String listUsers(Map<String, Object> map) {
            map.put("usuario", new Usuario());
            map.put("usuarioList", usuarioService.listUsuario());
            return "usuario";
     } 


    @RequestMapping(value = "/add", method = RequestMethod.POST)
     public String addUsuario(@ModelAttribute("user")
        Usuario user, BindingResult result) {
        usuarioService.addUsuario(user);
        return "redirect:/index";
     }

    @RequestMapping("/delete/{email}")
     public String deleteUsuario(@PathVariable("email")
     String email) {
            usuarioService.removeUsuario(email);
            return "redirect:/index";
     }

}

Usuario.jsp

<%@taglib uri="http://www.springframework.org/tags" prefix="spring"%>
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
<head>
 <title>Spring 3 MVC Series - Contact Manager</title>
</head>
<body>
<!-- 

<h3>Usuarios</h3>
<c:if test="${!empty usuarioList}">
<table class="data">
<tr>
 <th><spring:message code="label.firstname"/></th>
 <th><spring:message code="label.email"/></th>
 <th>&nbsp;</th>
</tr>
<c:forEach items="${usuarioList}" var="usuario">
 <tr>
 <td>${usuario.lastname}, ${usuario.firstname} </td>
 <td>${usuario.email}</td>
 <td><a href="delete/${usuario.email}">Eliminar</a></td>
 </tr>
</c:forEach>
</table>
</c:if> 

</body>
</html>

UsuarioServiceImpl.java(接口(interface)UsuarioService.java的实现)

@Service
public class UsuarioServiceImpl implements UsuarioService {

     @Autowired
     private UsuarioDAO UsuarioDAO;

     @Transactional
     public void addUsuario(Usuario user) {
     UsuarioDAO.addUsuario(user);
     }

     @Transactional
     public List<Usuario> listUsuario() {

     return UsuarioDAO.listUsuario();
     }

     @Transactional
     public void removeUsuario(String email) {
     UsuarioDAO.removeUsuario(email);
     }  

}

我不知道是否有必要继续使用 DAO...问题是错误命名为“Contact”，我什至根本不使用该名称(我使用“Usuario” ).是的，在你问之前，我确实替换了一些带有“联系人”一词的互联网代码，但我将它们全部替换为我的代码。所以也许这造成了困惑，但我现在真的迷路了。希望你能帮我。如果有什么你不明白的，请不要犹豫，尽管问。

非常感谢!

Answer 1

您只是将您的对象放入 map 中。您需要将对象放入 http 请求中。 Spring 具有模型对象 Model 和 ModelAndView 执行此操作，如下所示:-

<code>
@RequestMapping("/index")
     public String listUsers(Model model) {
            model.addAttribute("usuario", new Usuario());
            model.addAttribute("usuarioList", usuarioService.listUsuario());
            return "usuario";
     }

</code> 

或

<code>
@RequestMapping("/index")
     public ModelAndView listUsers() {
           ModelAndView mav = new ModelAndView("usuario");
            mav.addObject("usuario", new Usuario());
            mav.addObject("usuarioList", usuarioService.listUsuario());
            return mav;
     }
 </code>