以下內容翻譯自：https://www.tutorialspoint.com/springmvc/springmvc_dropdown.htm
說明：示例基于Spring MVC 4.1.6。
以下示例顯示如何使用Spring Web MVC框架在表單中使用Dropdown。首先，讓我們使用Eclipse IDE，并按照以下步驟使用Spring Web Framework開發基于動態窗體的Web應用程序：
| 步驟 | 描述 |
|---|---|
| 1 | 創建一個名為HelloWeb的項目，在一個包com.tutorialspoint下，如Spring MVC - Hello World Example章節所述。 |
| 2 | 在com.tutorialspoint包下創建一個Java類User，UserController。 |
| 3 | 在jsp子文件夾下創建一個視圖文件user.jsp，users.jsp。 |
| 4 | 最后一步是創建所有源和配置文件的內容并導出應用程序，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;@Controller public 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<String> getWebFrameworkList(){List<String> webFrameworkList = new ArrayList<String>();webFrameworkList.add("Spring MVC");webFrameworkList.add("Struts 1");webFrameworkList.add("Struts 2");webFrameworkList.add("Apache Wicket");return webFrameworkList;}@ModelAttribute("numbersList")public List<String> getNumbersList(){List<String> numbersList = new ArrayList<String>();numbersList.add("1");numbersList.add("2");numbersList.add("3");numbersList.add("4");return numbersList;}@ModelAttribute("countryList")public Map<String, String> getCountryList(){Map<String, String> countryList = new HashMap<String, String>();countryList.put("US", "United States");countryList.put("CH", "China");countryList.put("SG", "Singapore");countryList.put("MY", "Malaysia");return countryList;} }
這里第一個服務方法user()，我們已經通過名為“command”的ModelAndView對象中傳遞了一個空的User對象，因為如果您在JSP中使用<form:form>標簽，Spring框架將期望一個名為“command”的對象文件。所以當user()方法被調用時，它返回user.jsp視圖。
將在HelloWeb/addUser?URL上針對POST方法調用第二個服務方法addUser()。您將根據提交的信息準備您的模型對象。最后，將從服務方法返回“user”視圖，這將導致渲染users.jsp
user.jsp
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%> <html> <head><title>Spring MVC Form Handling</title> </head> <body><h2>User Information</h2> <form:form method="POST" action="/HelloWeb/addUser"><table><tr><td><form:label path="username">User Name</form:label></td><td><form:input path="username" /></td></tr><tr><td><form:label path="password">Age</form:label></td><td><form:password path="password" /></td></tr> <tr><td><form:label path="address">Address</form:label></td><td><form:textarea path="address" rows="5" cols="30" /></td></tr> <tr><td><form:label path="receivePaper">Subscribe Newsletter</form:label></td><td><form:checkbox path="receivePaper" /></td></tr> <tr><td><form:label path="favoriteFrameworks">Favorite Web Frameworks</form:label></td><td><form:checkboxes items="${webFrameworkList}" path="favoriteFrameworks" /></td> </tr><tr><td><form:label path="gender">Gender</form:label></td><td><form:radiobutton path="gender" value="M" label="Male" /><form:radiobutton path="gender" value="F" label="Female" /></td></tr><tr><td><form:label path="favoriteNumber">Favorite Number</form:label></td><td><form:radiobuttons path="favoriteNumber" items="${numbersList}" /> </td></tr><tr><td><form:label path="country">Country</form:label></td><td><form:select path="country"><form:option value="NONE" label="Select"/><form:options items="${countryList}" /></form:select> </td></tr> <tr><td colspan="2"><input type="submit" value="Submit"/></td></tr></table> </form:form> </body> </html>
這里我們使用<form:select />，<form:option />和<form:options />標簽來呈現HTML選擇。例如
<form:select path="country"><form:option value="NONE" label="Select"/><form:options items="${countryList}" /> </form:select>
它將呈現以下HTML內容。
<select id="country" name="country"><option value="NONE">Select</option><option value="US">United States</option><option value="CH">China</option><option value="MY">Malaysia</option><option value="SG">Singapore</option> </select>
users.jsp
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%> <html> <head><title>Spring MVC Form Handling</title> </head> <body><h2>Submitted User Information</h2><table><tr><td>Username</td><td>${username}</td></tr><tr><td>Password</td><td>${password}</td></tr> <tr><td>Address</td><td>${address}</td></tr> <tr><td>Subscribed to Newsletter</td><td>${receivePaper}</td></tr> <tr><td>Favorite Web Frameworks</td><td> <% String[] favoriteFrameworks = (String[])request.getAttribute("favoriteFrameworks");for(String framework: favoriteFrameworks) {out.println(framework);}%></td></tr> <tr><td>Gender</td><td>${(gender=="M"? "Male" : "Female")}</td></tr><tr><td>Favourite Number</td><td>${favoriteNumber}</td></tr> <tr><td>Country</td><td>${country}</td></tr> </table> </body> </html>
完成創建源文件和配置文件后，導出應用程序。右鍵單擊應用程序并使用Export->WAR File選項，并將您的HelloWeb.war文件保存在Tomcat的webapps文件夾中。
現在啟動您的Tomcat服務器，并確保您可以使用標準瀏覽器從webapps文件夾訪問其他網頁。現在嘗試URL?http://localhost:8080/HelloWeb/user，如果您的Spring Web應用程序的一切都很好，您應該會看到以下結果：
提交所需信息后，點擊提交按鈕提交表單。如果您的Spring Web應用程序的一切都很好，您應該會看到以下結果：
Maven示例：
https://github.com/easonjim/5_java_example/tree/master/springmvc/tutorialspoint/test11
==>如有問題，請聯系我：easonjim#163.com，或者下方發表評論。<==
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