Struts 2 - 合併標籤

假設您有兩個列表 A 和 B，其值分別為 A1、A2 和 B1、B2。合併這些列表將得到 A1、B1、A2、B2。

建立 Action 類

首先，讓我們建立一個名為 Employee.java 的簡單類，如下所示：

package com.tutorialspoint.struts2;

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

import org.apache.struts2.util.SubsetIteratorFilter.Decider;

public class Employee {
   private String name;
   private String department;

   public Employee(){}
   
   public Employee(String name,String department) {
      this.name = name;
      this.department = department;
   }
   
   private List employees;
   private List contractors;
	
   public String execute() {
      employees = new ArrayList();
      employees.add(new Employee("George","Recruitment"));
      employees.add(new Employee("Danielle","Accounts"));
      employees.add(new Employee("Melissa","Recruitment"));
      employees.add(new Employee("Rose","Accounts"));

      contractors = new ArrayList();
      contractors.add(new Employee("Mindy","Database"));
      contractors.add(new Employee("Vanessa","Network"));
      return "success";
   }

   public Decider getRecruitmentDecider() {
      return new Decider() {
         public boolean decide(Object element) throws Exception {
            Employee employee = (Employee)element;
            return employee.getDepartment().equals("Recruitment");
         }
      };
   }
   public String getName() {
      return name;
   }
   
   public void setName(String name) {
      this.name = name;
   }
   
   public String getDepartment() {
      return department;
   }
   
   public void setDepartment(String department) {
      this.department = department;
   }
   
   public List getEmployees() {
      return employees;
   }
   
   public void setEmployees(List employees) {
      this.employees = employees;
   }
   
   public List getContractors() {
      return contractors;
   }
   
   public void setContractors(List contractors) {
      this.contractors = contractors;
   }
	
}

Employee 類有兩個屬性 - **姓名** 和 **部門**，我們還有兩個員工列表 - 正式 **員工** 和 **合同工**。我們有一個名為 **getRecruitmentDecider** 的方法，它返回一個 Decider 物件。**Decider** 實現如果員工在 **招聘** 部門工作則返回 true，否則返回 **false**。

接下來，讓我們建立一個 **DepartmentComparator** 來比較 Employee 物件：

package com.tutorialspoint.struts2;

import java.util.Comparator;

public class DepartmentComparator implements Comparator {
   public int compare(Employee e1, Employee e2) {
      return e1.getDepartment().compareTo(e2.getDepartment());
   }

   @Override
   public int compare(Object arg0, Object arg1) {
      return 0;
   }
}

如上例所示，部門比較器根據部門的字母順序比較員工。

建立檢視

建立一個名為 **employee.jsp** 的檔案，內容如下：

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

<html>
   <head>
      <title>Employees</title>
   </head>
   
   <body>
      <b>Employees and Contractors Merged together</b>
      
      <br />
      
      <s:merge id = "allemployees">
         <s:param value = "employees" />
         <s:param value = "contractors" />
      </s:merge>
      
      <s:iterator value = "allemployees">
         <s:property value = "name"/>,
         <s:property value = "department"/><br/>
      </s:iterator>
   </body>
</html>

**merge** 標籤將兩個或多個列表作為引數。我們需要為 merge 提供一個 **id**，以便以後可以重用它。在這個例子中，我們將 employees 和 contractors 作為引數提供給 merge 標籤。然後，我們使用 "allemployees" id 迭代合併後的列表並列印員工詳細資訊。

配置檔案

你的 **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 = "employee" 
         class = "com.tutorialspoint.struts2.Employee"
         method = "execute">
         <result name = "success">/employee.jsp</result>
      </action>
   </package>
</struts>

你的 **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 目錄中。最後，啟動 Tomcat 伺服器並嘗試訪問 URL **https://:8080/HelloWorldStruts2/employee.action**。這將產生以下螢幕：

struts_control_tags.htm

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