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Struts2 iterator标签

2018-12-24 18:04 更新

创建Action类

首先让我们创建一个简单的类Employee.java，如下：

package cn.w3cschool.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类有两个属性：name和department，还有两个员工列表：永久的employees和contractors。我们有一个名为getRecruitmentDecider的方法，它返回一个Decider对象。如果employee在recruitment（招聘）部门工作，则Decider实现返回true，否则返回false。
接下来，让我们创建一个DepartmentComparator来比较Employee对象：

package cn.w3cschool.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;
	}
}

如上所示，部门比较器按字母顺序比较部门的员工。

创建视图

创建一个名为employee.jsp的文件，包含以下内容：

<%@ 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="cn.w3cschool.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>

让我们逐一了解下使用过的标签：

Iterator标签

我们使用iterator标签来迭代employee列表，提供“employees”属性作为iterator标签的源。在iterator标签中，我们可以访问employee列表中的Employee对象，打印员工的名字，以及他们的部门。

Sort标签

首先，我们将DepartmentComparator声明为bean，给这个bean命名为deptComparator。然后我们使用sort标签，指定“employees”列表作为源和指定“deptComparator”作为比较器使用。最后，按照前面的例子，迭代列表并打印员工名字。从输出中可以看到，将会打印按部门排序的员工列表。

Subset标签

subset标签用于获取列表或数组的子集。有两种类型的subset标签，在第一个示例中，我们使用recreutationDecider获取在招聘部门工作的员工列表（请参阅Employee.java中的getRecruitmentDecider()方法）。
在第二个例子中，我们不使用任何决策者，而是在列表中的元素2和3之后。subset标签接受两个参数“count”和“start”。“start”确定子集的起始点，“count”确定子集的长度。

配置文件

你的struts.xml应如下：

<?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="cn.w3cschool.struts2.Employee"
         method="execute">
         <result name="success">/employee.jsp</result>
      </action>
   </package>

</struts>

web.xml文件应如下：

<?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>

现在，右键单击项目名称，然后单击“Export”> “WAR File”以创建WAR文件。然后在Tomcat的webapps目录中部署WAR文件。最后，启动Tomcat服务器并尝试访问URL http://localhost:8080/HelloWorldStruts2/employee.action，将显示以下界面：

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