Struts2教學 » Struts2 merge標籤

Struts2 merge標籤

如果有兩個列表A和B的值，A1，A2和B1，B2。合並列表，會給出A1，B1，A2，B2。

建立動作類：

首先，讓我們建立一個簡單的類叫做Employee.java，它看起來像：

package com.yiibai.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 - name 和 department，我們也有兩個員工名單 - employees 和contractors。我們有一個方法叫做getRecruitmentDecider，返回Decider 物件。Decider 實現返回true，如果雇員招聘部門工作，否則返回false。

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

package com.yiibai.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;
	}
}

在上面的例子所示，部門比較的基礎上按字母順序排列的部門員工進行比較。

建立檢視

建立一個檔案叫做employee.jsp以下內容：

<%@ 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>

合併標記需要兩個或兩個以上的列表作為引數。我們需要給合併一個id，這樣我們就可以重用它。在這個例子中，我們提供了作為引數傳遞給員工和承包商的合併標籤。然後，我們使用“allemployees”ID合並列表遍歷並列印員工的細節。

組態檔案

struts.xml中應該像這樣：

<?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.yiibai.struts2.Employee"
         method="execute">
         <result name="success">/employee.jsp</result>
      </action>
   </package>

</struts>

web.xml中，應該像這樣：

<?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>

右鍵點選專案名稱，並單擊 Export > WAR File建立一個WAR檔案。然後部署此WAR在Tomcat的webapps目錄下。最後，啟動Tomcat伺服器和嘗試存取URL http://localhost:8080/HelloWorldStruts2/employee.action。這會給出以下畫面：

Struts merge tag