Spring Form 验证错误：java.lang.IllegalArgumentException：'items'不得为 null

我正在尝试Validate Spring形式，其中包括：

普通输入字段
控制器中设置选项的单选按钮(以后可能来自数据库(
选项也在控制器中设置的复选框
选择也在控制器中设置的字段

遵循方法 1 方法。

型：

public class Student {
    private Long id;
    @NotEmpty
    private String name;
    @NotEmpty
    private String address;
    @NotEmpty
    private String contactNumber;
    @NotEmpty
    private String grade;
    @NotEmpty
    private String gender;
    @NotEmpty
    @Email
    private String email;
    @NotEmpty
    private List<String> extraSubjects = new ArrayList<String>();
    /****  Corresponding getter setters ****/
}

控制器：-

@Controller
@RequestMapping("/student")
public class StudentController {
    private Logger logger = Logger.getLogger(StudentController.class);
    @RequestMapping("/home")
    public String getHomePage() {
        return "home";
    }
    @RequestMapping(value = "/add", method = RequestMethod.GET)
    public String addStudentForm(Model model) {
        Student student = new Student();
        model.addAttribute("studentForm", student);
        LinkedHashMap<Integer, String> gradeList = new LinkedHashMap<Integer, String>();
        gradeList.put(1, "Class 1");
        gradeList.put(2, "Class 2");
        gradeList.put(3, "Class 3");
        gradeList.put(4, "Class 4");
        gradeList.put(5, "Class 5");
        model.addAttribute("gradeList", gradeList);
        List<String> genderList = new ArrayList<String>();
        genderList.add("Male");
        genderList.add("Female");
        model.addAttribute("genderList", genderList);
        student.setGender("Male");
        List<String> extraSubjects = new ArrayList<String>();
        extraSubjects.add("Math II");
        extraSubjects.add("Population");
        List<String> extraSubjectsStd = new ArrayList<String>();
        extraSubjectsStd.add("Math II");
        extraSubjectsStd.add("Population");
        student.setExtraSubjects(extraSubjectsStd);
        extraSubjects.add("Computer");
        model.addAttribute("extraSubjects", extraSubjects);
        return "addstudent";
    }
    @RequestMapping(value = "/add", method = RequestMethod.POST)
    public String addStudent(
            @Valid @ModelAttribute("studentForm") Student student,
            BindingResult result) {
        if (result.hasErrors()) {
            logger.info("Returning add page with errors");
            return "addstudent";
        }
            //Stuffs to save in database 
        return "redirect:add";
    }
}

JSP页面：-

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring"%>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Insert title here</title>
<style>
.error {
    color: #ff0000;
}
.errorblock {
    color: #000;
    background-color: #ffEEEE;
    border: 3px solid #ff0000;
    padding: 8px;
    margin: 16px;
}
</style>
</head>
<body>
    <form:form action="add" method="post" commandName="studentForm">
        <form:errors path="*" cssClass="errorblock" element="div" />
        <table border="0">
            <tr>
                <td colspan="3" align="center"><h3>Add Student</h3></td>
            </tr>
            <tr>
                <td><form:label path="name">
                        <spring:message code="label.studentname" />
                    </form:label></td>
                <td><form:input path="name" /></td>
                <td><form:errors path="name" cssClass="error" /></td>
            </tr>
            <tr>
                <td><form:label path="address">
                        <spring:message code="label.address" />
                    </form:label></td>
                <td><form:input path="address" /></td>
                <td><form:errors path="address" cssClass="error" />
            </tr>
            <tr>
                <td>Contact Number:</td>
                <td><form:input path="contactNumber" /></td>
                <td><form:errors path="contactNumber" cssClass="error" />
            </tr>
            <tr>
                <td><form:label path="grade">
                        <spring:message code="label.grade" />
                    </form:label></td>
                <td><form:select path="grade">
                        <form:option value="" label="--- Select ---" />
                        <form:options items="${gradeList}" />
                    </form:select></td>
                <td><form:errors path="grade" cssClass="error" />
            </tr>
            <tr>
                <td>Gender:</td>
                <td><form:radiobuttons path="gender" items="${genderList}" />
                </td>
                <td><form:errors path="gender" cssClass="error" />
            </tr>
            <tr>
                <td>Extra Subjects:</td>
                <td><form:checkboxes items="${extraSubjects}"
                        path="extraSubjects" /></td>
                <td><form:errors path="extraSubjects" cssClass="error" />
            </tr>
            <tr>
                <td>Email Address:</td>
                <td><form:input items="${email}" path="email" /></td>
                <td><form:errors path="email" cssClass="error" />
            </tr>
            <tr>
                <td></td>
                <td align="center"><input type="submit" value="Save" /></td>
                <td></td>
            </tr>
        </table>
    </form:form>
</body>
</html>

现在，当我运行应用程序时，表单会在我perform get operation时加载。radio buttons, select fields, and checkboxes are loaded中的值，也已选中。如果我submit my form with no validation errors it works fine但是当我with validation errors发送表单时，我会收到以下错误：

堆栈跟踪：-

Jun 26, 2014 4:32:00 PM org.apache.catalina.core.ApplicationDispatcher invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.IllegalArgumentException: 'items' must not be null
    at org.springframework.util.Assert.notNull(Assert.java:112)
    at org.springframework.web.servlet.tags.form.AbstractMultiCheckedElementTag.setItems(AbstractMultiCheckedElementTag.java:85)
    at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspx_meth_form_005fradiobuttons_005f0(addstudent_jsp.java:810)
    at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspService(addstudent_jsp.java:360)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    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.doPost(FrameworkServlet.java:833)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
DEBUG org.springframework.web.servlet.DispatcherServlet- Error rendering view [org.springframework.web.servlet.view.JstlView: name 'addstudent'; URL [/WEB-INF/pages/addstudent.jsp]] in DispatcherServlet with name 'mvc-dispatcher'
org.apache.jasper.JasperException: An exception occurred processing JSP page /WEB-INF/pages/addstudent.jsp at line 62
59:             </tr>
60:             <tr>
61:                 <td>Gender:</td>
62:                 <td><form:radiobuttons path="gender" items="${genderList}" />
63:                 </td>
64:                 <td><form:errors path="gender" cssClass="error" />
65:             </tr>    
Stacktrace:
        at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
        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.doPost(FrameworkServlet.java:833)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)
    Caused by: java.lang.IllegalArgumentException: 'items' must not be null
        at org.springframework.util.Assert.notNull(Assert.java:112)
        at org.springframework.web.servlet.tags.form.AbstractMultiCheckedElementTag.setItems(AbstractMultiCheckedElementTag.java:85)
        at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspx_meth_form_005fradiobuttons_005f0(addstudent_jsp.java:810)
        at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspService(addstudent_jsp.java:360)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
        ... 42 more
    Jun 26, 2014 4:32:00 PM org.apache.catalina.core.StandardWrapperValve invoke
    SEVERE: Servlet.service() for servlet [mvc-dispatcher] in context with path [/sms] threw exception [An exception occurred processing JSP page /WEB-INF/pages/addstudent.jsp at line 62
    59:             </tr>
    60:             <tr>
    61:                 <td>Gender:</td>
    62:                 <td><form:radiobuttons path="gender" items="${genderList}" />
    63:                 </td>
    64:                 <td><form:errors path="gender" cssClass="error" />
    65:             </tr>

    Stacktrace:] with root cause
    java.lang.IllegalArgumentException: 'items' must not be null
        at org.springframework.util.Assert.notNull(Assert.java:112)
        at org.springframework.web.servlet.tags.form.AbstractMultiCheckedElementTag.setItems(AbstractMultiCheckedElementTag.java:85)
        at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspx_meth_form_005fradiobuttons_005f0(addstudent_jsp.java:810)
        at org.apache.jsp.WEB_002dINF.pages.addstudent_jsp._jspService(addstudent_jsp.java:360)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
        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.doPost(FrameworkServlet.java:833)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:807)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

我

能够弄清楚我用于specifying genders, gradeList, extraSubjects的List似乎是NULL after post request。

如果验证失败，如何在发布后再次呈现这些值？
我是否也必须像在 GET 方法中一样在 POST 方法的列表中设置值？

在你得到部分时，你填充你的模型，不仅用studentForm，还用genderList、gradeList和extraSubjects。并且您在 jsp 中使用所有内容。

在 post 部分中，您有一个由请求中的参数初始化的studentForm。但是您永远不会初始化列表。所以在JSP中，${gradeList}，${genderList}和${extraSubjects}，并且全部为空，所以错误。

如果验证失败，则必须在 addStudent 中初始化三个列表，然后再转发到视图。你可以按照Neil McGuigan的建议来做到这一点，即通过spring自动填充模型，或者通过自己填充它。例如，您可以有：

void initLists(Model model) {
    LinkedHashMap<Integer, String> gradeList = new LinkedHashMap<Integer, String>();
    gradeList.put(1, "Class 1");
    gradeList.put(2, "Class 2");
    gradeList.put(3, "Class 3");
    gradeList.put(4, "Class 4");
    gradeList.put(5, "Class 5");
    model.addAttribute("gradeList", gradeList);
    List<String> genderList = new ArrayList<String>();
    genderList.add("Male");
    genderList.add("Female");
    model.addAttribute("genderList", genderList);
    List<String> extraSubjects = new ArrayList<String>();
    extraSubjects.add("Math II");
    extraSubjects.add("Population");
    extraSubjects.add("Computer");
    model.addAttribute("extraSubjects", extraSubjects);
}

并用addStudentForm和addStudent打电话给initLists.最后一个示例代码：

@RequestMapping(value = "/add", method = RequestMethod.POST)
public String addStudent(
        @Valid @ModelAttribute("studentForm") Student student,
        BindingResult result, Model model) {
    if (result.hasErrors()) {
        logger.info("Returning add page with errors");
        initLists(model);
        return "addstudent";
    }
        //Stuffs to save in database 
    return "redirect:add";
}

当然，一旦您从那里调用initLists，所有列表初始化都应该从addStudentForm中删除......

将控制器更改为如下所示：

@Controller
@RequestMapping("/student")
@SessionAttributes({"studentForm", "gradeList", "genderList", "extraSubjects"})
public class StudentController {
    private Logger logger = Logger.getLogger(StudentController.class);
    @ModelAttribute("studentForm")
    Student getStudent() {
      Student student = new Student();
      student.setGender("Male");
      List<String> extraSubjectsStd = new ArrayList<String>();
      extraSubjectsStd.add("Math II");
      extraSubjectsStd.add("Population");
      student.setExtraSubjects(extraSubjectsStd);
      return student;
    }
    @ModelAttribute("gradeList")
    GradeList getGradeList() {
        LinkedHashMap<Integer, String> gradeList = new LinkedHashMap<Integer, String>();
        gradeList.put(1, "Class 1");
        gradeList.put(2, "Class 2");
        gradeList.put(3, "Class 3");
        gradeList.put(4, "Class 4");
        gradeList.put(5, "Class 5");
        return gradeList;
    }
    @ModelAttribute("genderList")
    List<String> getGenderList() {
        List<String> genderList = new ArrayList<String>();
        genderList.add("Male");
        genderList.add("Female");
        return genderList;
    }
    @ModelAttribute("extraSubjects")
    List<String> getExtraSubjects() {
        List<String> extraSubjects = new ArrayList<String>();
        extraSubjects.add("Math II");
        extraSubjects.add("Population");
        extraSubjects.add("Computer");
        return extraSubjects;
    }
    @RequestMapping("/home")
    public String getHomePage() {
        return "home";
    }
    @RequestMapping(value = "/add", method = RequestMethod.GET)
    public String addStudentForm() {
        return "addstudent";
    }
    @RequestMapping(value = "/add", method = RequestMethod.POST)
    public String addStudent(
            @Valid @ModelAttribute("studentForm") Student student,
            BindingResult result,
            SessionStatus sessionStatus) {
        if (result.hasErrors()) {
            logger.info("Returning add page with errors");
            return "addstudent";
        }
        sessionStatus.setComplete();
            //Stuffs to save in database 
        return "redirect:add";
    }
}

当我们在它的时候：

像gradeList这样的数据可能应该在数据库中。
/学生网址应为/学生
主页应位于其自己的控制器中

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