使用多个下拉菜单处理 Spring MVC 表单的问题答案

【问题标题】：Issue processing Spring MVC form with multiple dropdown menus使用多个下拉菜单处理 Spring MVC 表单的问题
【发布时间】：2015-02-05 01:01:06
【问题描述】：

我有一个带有两个下拉菜单的表格，用于选择学生和学生将要学习的课程。当我使用此表单加载页面时，我会收到将在下面包含的错误。

这是我的 jsp 表单。

assignStudent.jsp

<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<%@include file="header.jsp"%>
<p>
<h2>Assign a Student to a Course</h2>
<br />
<form:form method="POST" action="/myApp/assignStudent">
<table>
    <tr>
        <th>Student</th>
        <th>Course</th>
    </tr>
    <tr>
        <td>
            <form:select path="studentMap" items="${studentMap}">
            </form:select>
        </td>
        <td>
            <form:select path="courseMap" items="${courseMap}">
            </form:select>
        </td>
    </tr>
    <tr>
        <td align="center" colspan="2"><input type="submit" value="Submit" /></td>
    </tr>
    <tr>
</table>
</form:form>
</p>
<%@include file="footer.jsp"%>

这是我一直在修改的控制器类的相关部分：

@RequestMapping(value = "/assignStudent", method = RequestMethod.GET)
public ModelAndView enrollInCourse()
{
    Map<Integer, String> studentMap = new HashMap<Integer, String>();

    //Create a map to put into the student dropdown menu
    for (Student s : studentDAO.allStudents())
    {
        String fullName = s.getFirstName() + " " + s.getLastName();

        studentMap.put(s.getStudentID(), fullName);
    }

    Map<Integer, String> courseMap = new HashMap<Integer, String>();

    //Create a map to put into the course dropdown menu
    for (Course c : courseDAO.allCourses())
    {           
        courseMap.put(c.getCourseID(), c.getCourseName());
    }

    ModelAndView model = new ModelAndView("assignStudent", "command", new StudentCourse());

    model.addObject("studentMap", studentMap);
    model.addObject("courseMap", courseMap);

    return model;
}

以下是我得到的错误信息：

HTTP 状态 500 - 处理 JSP 页面时发生异常 /WEB-INF/jsp/assignStudent.jsp 第 14 行

输入异常报告

消息处理JSP页面发生异常 /WEB-INF/jsp/assignStudent.jsp 第 14 行

描述服务器遇到阻止它的内部错误完成此请求。

异常

org.apache.jasper.JasperException：发生异常处理 JSP 页面 /WEB-INF/jsp/assignStudent.jsp 在第 14 行

 11:    </tr> 
 12:    <tr> 
 13:        <td> 
 14:            <form:select path="studentMap" items="${studentMap}"> 
 15:            </form:select> 
 16:        </td>
 17:        <td>

堆栈跟踪： org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:725) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168) org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303) org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228) org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) javax.servlet.http.HttpServlet.service(HttpServlet.java:618) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) javax.servlet.http.HttpServlet.service(HttpServlet.java:725) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 根本原因

org.springframework.beans.NotReadablePropertyException: 无效 bean 类 [com.myapp.StudentCourse] 的属性“studentMap”：Bean 属性 'studentMap' 不可读或具有无效的 getter 方法： getter 的返回类型是否与 getter 的参数类型匹配二传手？ org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:726) org.springframework.beans.BeanWrapperImpl.getPropertyValue(BeanWrapperImpl.java:717) org.springframework.validation.AbstractPropertyBindingResult.getActualFieldValue(AbstractPropertyBindingResult.java:99) org.springframework.validation.AbstractBindingResult.getFieldValue(AbstractBindingResult.java:229) org.springframework.web.servlet.support.BindStatus.(BindStatus.java:120) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:154) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.autogenerateId(AbstractDataBoundFormElementTag.java:141) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.resolveId(AbstractDataBoundFormElementTag.java:132) org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:116) org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:422) org.springframework.web.servlet.tags.form.SelectTag.writeTagContent(SelectTag.java:194) org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84) org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80) org.apache.jsp.WEB_002dINF.jsp.assignStudent_jsp._jspx_meth_form_005fselect_005f0(assignStudent_jsp.java:267) org.apache.jsp.WEB_002dINF.jsp.assignStudent_jsp._jspx_meth_form_005fform_005f0(assignStudent_jsp.java:218) org.apache.jsp.WEB_002dINF.jsp.assignStudent_jsp._jspService(assignStudent_jsp.java:122) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:725) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:725) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168) org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303) org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228) org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011) org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955) org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877) org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) javax.servlet.http.HttpServlet.service(HttpServlet.java:618) org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) javax.servlet.http.HttpServlet.service(HttpServlet.java:725) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

我对 Spring MVC 还很陌生，所以非常感谢您的建议！

【问题讨论】：

标签： java spring jsp spring-mvc servlets

【解决方案1】：

您没有显示 StudentCourse 课程，而是根据根异常

org.springframework.beans.NotReadablePropertyException: Invalid property 'studentMap' of bean class [com.myapp.StudentCourse]: Bean property 'studentMap' is not readable or has an invalid getter method: Does the return type of the getter match the parameter type of the setter?

你的 StudentCourse 类没有 studentMap 属性，或者它缺少它的 setter 或者它被命名为 setStudentMap 以外的其他东西，所以解决方案是向你的类添加一个 studentMap 属性并编写一个 setter 和一个 getter遵循正确的命名规则（setStudentMap 和 getStudentMap）。

但是，如果您不希望 StudentCourse 类中包含 studentMap 属性，则可以使用 public ModelAndView(View view, java.util.Map model) 构造函数并传递您的 StudentCourse、studentMap 和 courseMap 对象。

【讨论】：