Question

我正在尝试在Spring MVC中运行一个项目。这是代码

的index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/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>Welcome to Spring Web MVC project</title>
    </head>

    <body>
        <h1>Spring 3 Register!</h1>
        <a href="register.htm">click</a>
        <form:form action="${pageContext.request.contextPath}/register" method="POST" modelAttribute="userForm">
            <table>
                <tr>
                    <td colspan="2" align="center">Spring MVC Form Demo - Registration</td>
                </tr>
                <tr>
                    <td>User Name</td>
                    <td><form:input path="username" /></td>
                </tr>
                <tr>
                    <td>Password</td>
                    <td><form:password path="password" /></td>
                </tr>
                <tr>
                    <td>Email</td>
                    <td><form:input path="email" /></td>
                </tr>
                <tr>
                    <td>BirthDate (mm/dd/yyyy)</td>
                    <td><form:input path="birthDate" /></td>
                </tr>
                <tr>
                    <td>Profession</td>
                    <td><form:select path="profession" items="${professionList}" /></td>
                </tr>
                <tr>
                    <td colspan="2" align="center"><input type="submit" value="Register" /></td>
                </tr>

            </table>
        </form:form>
    </body>
</html>

RegistrationController.java

package RegisterInfo;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 *
 * @author Harshit Shrivastava
 */
import RegisterInfo.model.User;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.ui.Model;

@Controller
@RequestMapping(value = "/register")
public class RegistrationController {

    @RequestMapping(method = RequestMethod.GET)
    public String viewRegistration(Model model)
    {
        User userForm = new User();
                model.addAttribute("userForm", new User());

                List<String> professionList = new ArrayList();
                professionList.add("Developer");
                professionList.add("Designer");
                professionList.add("IT Manager");
                model.put("professionList", professionList);
        return "index";
    }
    @InitBinder
    public void initBinder(WebDataBinder binder) {
         SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
         sdf.setLenient(true);
         binder.registerCustomEditor(Date.class, new CustomDateEditor(sdf, true));
    }
    @RequestMapping(method = RequestMethod.POST)
    public ModelAndView processRegistration(@ModelAttribute("userForm") User user, Map<String, Object> model)
    {       
        model.addAttribute("username", user.getUserName());
        model.addAttribute("password", user.getPassword());
        model.addAttribute("birthDate", user.getBirthDate());
        model.addAttribute("email", user.getEmail());
        model.addAttribute("profession", user.getProfession());                 
            return new ModelAndView("RegisterSuccess","userForm",new User());
    }
}

User.java

package RegisterInfo.model;

import java.util.Date;

public class User {
    private String username;
    private String password;
    private String email;
    private Date birthDate;
    private String profession;

    public String getUserName()
    {
        return username;
    }
    public void setUserName(String username)
    {
        this.username = username;
    }
        public String getPassword()
    {
        return password;
    }
    public void setPassword(String password)
    {
        this.password = password;
    }
        public String getEmail()
    {
        return email;
    }
    public void setEmail(String email)
    {
        this.email = email;
    }
        public Date getBirthDate()
    {
        return birthDate;
    }
    public void setBirthDate(Date birthDate)
    {
        this.birthDate = birthDate;
    }
        public String getProfession()
    {
        return profession;
    }
    public void setProfession(String profession)
    {
        this.profession = profession;
    }
}

RegisterSuccess.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/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>Welcome to Spring Web MVC project</title>
    </head>

    <body>
        <h1>Register Success!</h1>
            <table>
                <tr>
                    <td>User Name</td>
                    <td>${username}</td>
                </tr>
                <tr>
                    <td>Password</td>
                    <td>${password}</td>
                </tr>
                <tr>
                    <td>Email</td>
                    <td>${email}</td>
                </tr>
                <tr>
                    <td>BirthDate (mm/dd/yyyy)</td>
                    <td>${birthDate}</td>
                </tr>
                <tr>
                    <td>Profession</td>
                    <td>${profession}</td>
                </tr>
            </table>
    </body>
</html>

在上面的程序中，我可以打印所有字段但不能打印日期，即BirthDate。为什么不打印？

Answer 1

您忘记将已填充属性的model添加到以ModelAndView方法返回的新创建的processRegistration。您在渲染视图时获得了NullPointerException，因为Model中没有要显示的属性。

这是固定方法：

@RequestMapping(method = RequestMethod.POST)
public ModelAndView processRegistration(@ModelAttribute("userForm") User user, Map<String, Object> model)
{       
    model.addAttribute("username", user.getUserName());
    model.addAttribute("password", user.getPassword());
    model.addAttribute("birthDate", user.getBirthDate());
    model.addAttribute("email", user.getEmail());
    model.addAttribute("profession", user.getProfession());
    model.addAttribute("userForm", new User());                 
    return new ModelAndView("RegisterSuccess",model);
}

此外，如果仍然发生NullPointerException，您可以在RegisterSuccess.jsp中执行此操作：

<%@page contentType="text/html" pageEncoding="UTF-8" %>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!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>Welcome to Spring Web MVC project</title>
</head>

<body>
<h1>Register Success!</h1>
<table>
    <tr>
        <td>User Name</td>
        <td><c:if test="${not empty username}"> ${username}</c:if></td>
    </tr>
    <tr>
        <td>Password</td>
        <td><c:if test="${not empty password}">${password}</c:if></td>
    </tr>
    <tr>
        <td>Email</td>
        <td><c:if test="${not empty email}">${email}</c:if></td>
    </tr>
    <tr>
        <td>BirthDate (mm/dd/yyyy)</td>
        <td><c:if test="${not empty birthDate}">${birthDate}</c:if></td>
    </tr>
    <tr>
        <td>Profession</td>
        <td><c:if test="${not empty profession}">${profession}</c:if></td>
    </tr>
</table>
</body>
</html>

如果您看到其中一个参数未显示，则表示它具有空值。

Spring MVC Display Date变量

1 个答案: