Spring MVC-表单（Form）标签-下拉框（Dropdown）示例（转载实践）-白红宇

以下内容翻译自：

说明：示例基于Spring MVC 4.1.6。

以下示例显示如何使用Spring Web MVC框架在表单中使用Dropdown。首先，让我们使用Eclipse IDE，并按照以下步骤使用Spring Web Framework开发基于动态窗体的Web应用程序：

步骤	描述
1	创建一个名为HelloWeb的项目，在一个包com.tutorialspoint下，如Spring MVC - Hello World Example章节所述。
2	在com.tutorialspoint包下创建一个Java类User，UserController。
3	在jsp子文件夹下创建一个视图文件user.jsp，users.jsp。
4	最后一步是创建所有源和配置文件的内容并导出应用程序，如下所述。

User.java

package com.tutorialspoint;public class User {       private String username;   private String password;   private String address;   private boolean receivePaper;   private String [] favoriteFrameworks;      private String gender;   private String favoriteNumber;   private String country;      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 getAddress() {      return address;   }   public void setAddress(String address) {      this.address = address;   }   public boolean isReceivePaper() {      return receivePaper;   }   public void setReceivePaper(boolean receivePaper) {      this.receivePaper = receivePaper;   }   public String[] getFavoriteFrameworks() {      return favoriteFrameworks;   }   public void setFavoriteFrameworks(String[] favoriteFrameworks) {      this.favoriteFrameworks = favoriteFrameworks;   }   public String getGender() {      return gender;   }   public void setGender(String gender) {      this.gender = gender;   }   public String getFavoriteNumber() {      return favoriteNumber;   }   public void setFavoriteNumber(String favoriteNumber) {      this.favoriteNumber = favoriteNumber;   }   public String getCountry() {      return country;   }   public void setCountry(String country) {      this.country = country;   }}

UserController.java

package com.tutorialspoint;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;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.web.servlet.ModelAndView;import org.springframework.ui.ModelMap;@Controllerpublic class UserController {   @RequestMapping(value = "/user", method = RequestMethod.GET)   public ModelAndView user() {      User user = new User();            user.setFavoriteFrameworks((new String []{"Spring MVC","Struts 2"}));      user.setGender("M");      ModelAndView modelAndView = new ModelAndView("user", "command", user);      return modelAndView;   }   @RequestMapping(value = "/addUser", method = RequestMethod.POST)   public String addUser(@ModelAttribute("SpringWeb")User user,       ModelMap model) {      model.addAttribute("username", user.getUsername());      model.addAttribute("password", user.getPassword());      model.addAttribute("address", user.getAddress());      model.addAttribute("receivePaper", user.isReceivePaper());      model.addAttribute("favoriteFrameworks", user.getFavoriteFrameworks());      model.addAttribute("gender", user.getGender());      model.addAttribute("favoriteNumber", user.getFavoriteNumber());      model.addAttribute("country", user.getCountry());           return "users";   }      @ModelAttribute("webFrameworkList")   public List
     
       getWebFrameworkList()   {      List
      
        webFrameworkList = new ArrayList
       
        ();      webFrameworkList.add("Spring MVC");      webFrameworkList.add("Struts 1");      webFrameworkList.add("Struts 2");      webFrameworkList.add("Apache Wicket");      return webFrameworkList;   }      @ModelAttribute("numbersList")   public List
        
          getNumbersList()   {      List
         
           numbersList = new ArrayList
          
           (); numbersList.add("1"); numbersList.add("2"); numbersList.add("3"); numbersList.add("4"); return numbersList; } @ModelAttribute("countryList") public Map
           
             getCountryList() { Map
            
              countryList = new HashMap
             
              (); countryList.put("US", "United States"); countryList.put("CH", "China"); countryList.put("SG", "Singapore"); countryList.put("MY", "Malaysia");return countryList; }}

这里第一个服务方法user()，我们已经通过名为“command”的ModelAndView对象中传递了一个空的User对象，因为如果您在JSP中使用<form:form>标签，Spring框架将期望一个名为“command”的对象文件。所以当user()方法被调用时，它返回user.jsp视图。

将在HelloWeb/addUser URL上针对POST方法调用第二个服务方法addUser()。您将根据提交的信息准备您的模型对象。最后，将从服务方法返回“user”视图，这将导致渲染users.jsp

user.jsp

<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>   Spring MVC Form HandlingUser Information
        
      
                                       
          
           User Name
                            
                        
                                
          
           Age
                            
                        
                                  
          
           Address
                            
                        
                                  
          
           Subscribe Newsletter
                            
                        
                                 
          
           Favorite Web Frameworks
                            
                               
                                
          
           Gender
                                        
                      
                                 
                                
          
           Favorite Number
                                        
                                             
                                
          
           Country

这里我们使用<form:select />，<form:option />和<form:options />标签来呈现HTML选择。例如

它将呈现以下HTML内容。

users.jsp

<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>    Spring MVC Form HandlingSubmitted User Information
   
     
                                    Username                  ${username}              
                              Password                  ${password}              
                                  Address                  ${address}              
                                Subscribed to Newsletter                  ${receivePaper}              
                                  Favorite Web Frameworks                   <% String[] favoriteFrameworks = (String[])request.getAttribute("favoriteFrameworks");            for(String framework: favoriteFrameworks) {               out.println(framework);            }         %>              
                                        Gender                  ${(gender=="M"? "Male" : "Female")}              
                              Favourite Number                  ${favoriteNumber}              
                                 Country                  ${country}

完成创建源文件和配置文件后，导出应用程序。右键单击应用程序并使用Export->WAR File选项，并将您的HelloWeb.war文件保存在Tomcat的webapps文件夹中。

现在启动您的Tomcat服务器，并确保您可以使用标准浏览器从webapps文件夹访问其他网页。现在尝试URL http://localhost:8080/HelloWeb/user，如果您的Spring Web应用程序的一切都很好，您应该会看到以下结果：

提交所需信息后，点击提交按钮提交表单。如果您的Spring Web应用程序的一切都很好，您应该会看到以下结果：

Maven示例：

==>如有问题，请联系我：easonjim#163.com，或者下方发表评论。<==

User Name
Age
Address
Subscribe Newsletter
Favorite Web Frameworks
Gender
Favorite Number
Country

Username	${username}
Password	${password}
Address	${address}
Subscribed to Newsletter	${receivePaper}
Favorite Web Frameworks	<% String[] favoriteFrameworks = (String[])request.getAttribute("favoriteFrameworks"); for(String framework: favoriteFrameworks) { out.println(framework); } %>
Gender	${(gender=="M"? "Male" : "Female")}
Favourite Number	${favoriteNumber}
Country	${country}