Struts 2 - Action 標籤

action 標籤允許程式設計師從檢視頁面執行一個 action。他們可以透過指定 action 名稱來實現這一點。他們可以將“executeResult”引數設定為“true”以直接在檢視中呈現結果。或者，他們可以將此引數設定為“false”，但利用 action 方法公開的請求屬性。

建立 Action 類

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

讓我們使用HelloWorld.jsp來演示generator標籤的使用 -

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

<html>
   <head>
      <title>Hello World</title>
   </head>
   
   <body>
      <h2>Example of Generator Tag</h2>
      <h3>The colours of rainbow:</h3>

      <s:generator val = "%{'Violet,Indigo,Blue,
         Green,Yellow,Orange,Red '}" count = "7" separator = ",">
         
         <s:iterator>
            <s:property /><br/>
         </s:iterator>
      </s:generator>	
   </body>
</html>

接下來，讓我們使用以下內容建立employees.jsp -

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

<html>
   <head>
      <title>Employees</title>
   </head>
   
   <body>
      <s:action name = "hello" executeresult = "true">
         Output from Hello:  <br />
      </s:action>
   </body>
</html>

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>
      
      <action name = "employee" 
         class = "com.tutorialspoint.struts2.Employee" 
         method = "execute">
         <result name = "success">/employee.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>

右鍵單擊專案名稱並點選匯出 > WAR 檔案以建立 WAR 檔案。然後將此 WAR 部署到 Tomcat 的 webapps 目錄中。最後，啟動 Tomcat 伺服器並嘗試訪問 URL https://:8080/HelloWorldStruts2/employee.action。這將生成以下螢幕 -

如您在這個例子中看到的，我們已將 executeResult 的值指定為“true”。因此，hello.action 的結果直接在頁面中呈現。HelloWorld.jsp 列印彩虹的顏色 - 現在在 employee.jsp 中呈現。

現在，讓我們稍微修改一下 HelloWorldAction.java -

package com.tutorialspoint.struts2;

import java.util.ArrayList;
import java.util.List;

import org.apache.struts2.ServletActionContext;

public class HelloWorldAction {
   private String name;
   public String execute() {
      List names = new ArrayList();
      names.add("Robert");
      names.add("Page");
      names.add("Kate");
      ServletActionContext.getRequest().setAttribute("names", names);
      return "success";
   }
   
   public String getName() {
      return name;
   }
   
   public void setName(String name) {
      this.name = name;
   }
}

最後，修改 employee.jsp 如下所示 -

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

<html>
   <head>
      <title>Employees</title>
   </head>
   
   <body>
      
      <s:action name = "hello" executeresult = "false">
         Output from Hello:  <br />
      </s:action>
      
      <s:iterator value = "#attr.names">
         <s:property /><br />
      </s:iterator>

   </body>
</html>

再次，右鍵單擊專案名稱並點選匯出 > WAR 檔案以建立 WAR 檔案。然後將此 WAR 部署到 Tomcat 的 webapps 目錄中。最後，啟動 Tomcat 伺服器並嘗試訪問 URL https://:8080/HelloWorldStruts2/employee.action。這將生成以下螢幕 -

struts_data_tags.htm

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