Struts 2 - if 和 else 標籤

package com.tutorialspoint.struts2;

public class HelloWorldAction {
   private String name;

   public String execute() throws Exception {
      return "success";
   }
   
   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }
}

建立檢視

讓我們建立如下index.jsp檔案：

<%@ page language = "java" contentType = "text/html; charset = ISO-8859-1"
  pageEncoding = "ISO-8859-1"%>
<%@ taglib prefix = "s" uri = "/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 
   "http://www.w3.org/TR/html4/loose.dtd">

<html>
   <head>
      lt;title>Hello World</title>
   </head>
   
   <body>
      <h1>Hello World From Struts2</h1>
      <form action = "hello">
         <label for = "name">Please pick a name</label><br/>
         <select name = "name">
            <option name = "Mike">Mike</option>
            <option name = "Jason">Jason</option>
            <option name = "Mark">Mark</option>
         </select>
         <input type = "submit" value = "Say Hello"/>
      </form>
   </body>
</html>

接下來，讓我們建立HelloWorld.jsp來演示if、else和elseif標籤的使用：

<%@ page contentType = "text/html; charset = UTF-8" %>
<%@ taglib prefix = "s" uri = "/struts-tags" %>

<html>
   <head>
      <title>Example of If and Else</title>
   </head>
   
   <body>
      <b>Example of If and Else</b><br/>
      
      <s:if test = "name=='Mike'">
         You have selected 'Mike'. 
      </s:if>
      
      <s:elseif test = "name=='Jason'">
         You have selected 'Jason'
      </s:elseif>
      
      <s:else>
         You have not selected 'Mike' or 'Jason'.
      </s:else>
   </body>
</html>

這裡，“if”標籤如果“test”屬性中指定的條件返回true，則返回true。在本例中，我們將它與“Mike”進行比較。如果名稱是Mike，則標籤返回true，我們列印字串；否則，執行“elseif”塊，如果該條件也不滿足，則執行else塊。這與Java語言中常用的if、else if和else沒有什麼不同。

配置檔案

您的struts.xml應該如下所示：

<?xml version = "1.0" Encoding = "UTF-8"?>
<!DOCTYPE struts PUBLIC
   "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
   "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
   <constant name = "struts.devMode" value = "true" />
   <package name = "helloworld" extends = "struts-default">
     
      <action name = "hello" 
         class = "com.tutorialspoint.struts2.HelloWorldAction" 
         method = "execute">
         <result name = "success">/HelloWorld.jsp</result>
      </action>

   </package>
</struts>

您的web.xml應該如下所示：

<?xml version = "1.0" Encoding = "UTF-8"?>
<web-app xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
   xmlns = "http://java.sun.com/xml/ns/javaee" 
   xmlns:web = "http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   xsi:schemaLocation = "http://java.sun.com/xml/ns/javaee 
   http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
   id = "WebApp_ID" version = "3.0">
   
   <display-name>Struts 2</display-name>
   
   <welcome-file-list>
      <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>
   
   <filter>
      <filter-name>struts2</filter-name>
      <filter-class>
         org.apache.struts2.dispatcher.FilterDispatcher
      </filter-class>
   </filter>

   <filter-mapping>
      <filter-name>struts2</filter-name>
      <url-pattern>/*</url-pattern>
   </filter-mapping>
</web-app>

右鍵單擊專案名稱，然後單擊匯出 > WAR 檔案以建立 WAR 檔案。然後將此 WAR 部署到 Tomcat 的 webapps 目錄。最後，啟動 Tomcat 伺服器並嘗試訪問 URL https://:8080/HelloWorldStruts2/index.jsp。這將產生以下螢幕：

現在選擇“Mark”並提交頁面。您應該會看到下一頁。

struts_control_tags.htm

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Struts 2 - if 和 else 標籤

建立Action類

建立檢視

配置檔案