Struts2 iterator標籤


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 有以下內容:

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Employees</title>
</head>
<body>
<b>Example of Iterator Tag</b><br/>
<s:iterator value="employees">
	<s:property value="name"/> , 
	<s:property value="department"/><br/>
</s:iterator>
<br/><br/>
<b>Employees sorted by Department</b><br/>

<s:bean name="com.yiibai.struts2.DepartmentComparator" 
   var="deptComparator" />

<s:sort comparator="deptComparator" source="employees">
   <s:iterator>
      <s:property value="name"/> , 
      <s:property value="department"/><br/>
   </s:iterator>
</s:sort>
<br/><br/>
<b>SubSet Tag - Employees working in Recruitment department </b><br/>
<s:subset decider="recruitmentDecider" source="employees">
   <s:iterator>
      <s:property value="name"/> , 
      <s:property value="department"/><br/>
   </s:iterator>
</s:subset>
<br/><br/>
<b>SubSet Tag - Employees 2 and 3 </b><br/>
<s:subset start="1" count="2" source="employees">
   <s:iterator>
      <s:property value="name"/> , 
      <s:property value="department"/><br/>
   </s:iterator>
</s:subset>
</body>
</html>

讓我們通過使用一個標籤:

iterator標籤

我們使用iterator標籤要經過員工列表。我們提供“employees”屬性iterator標籤作為源。在body疊代器標籤,我們現在有存取Employee物件在員工列表。我們列印隨後他們部門的員工的名字。

SORT 標籤

首先,我們宣告一個bean DepartmentComparator。我們給這個bean名稱deptComparator。然後,我們使用的形式的標記,並指定作為源和作為比較器使用的的“deptComparator”的“雇員”列表中。然後,按照前面的例子中,我們遍歷列表和列印員工。正如可以看到的輸出,列印部門排序的員工列表

SUBSET 標籤

用來獲取的列表或陣列的一個子集,該子集標記。我們有兩種口味的子標籤。在第一個例子,我們使用recrutimentDecider 招聘部(請參閱getRecruitmentDecider()方法在Employee.java)工作的員工以獲取列表。

在第二個例子中,我們沒有使用任何決策者,而是我們所追求的元素列表中的第2和第3。子標記需要兩個引數“count”和“start”。 “start”的子集確定的起點,“count”的子集確定的長度。

組態檔案

struts.xml 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 iterator tag