Struts 2 - Iterator 标签
创建操作类
首先让我们创建一个名为 Employee.java 的简单类，它看起来像 −
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 类有两个属性 - name 和 department，我们还有两个 employees 列表 - 永久 员工和合同工。我们有一个名为 getRecruitmentDecider 的方法，它返回一个 Decider 对象。
如果员工在 recruitment 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 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，部门比较器按字母顺序根据部门比较员工。
创建视图
创建一个名为 employee.jsp 的文件，其中包含以下内容 −
<%@ 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 = "com.tutorialspoint.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>
让我们逐一查看使用的标签 −
迭代器标签
我们使用 迭代器 标签查看员工列表。我们将"员工"属性作为迭代器标签的源。在迭代器标签的主体中，我们现在可以访问员工列表中的员工对象。我们打印员工的姓名，然后是他们的部门。
排序标签
首先，我们将 DepartmentComparator 声明为 bean。我们给这个 bean 命名为 deptComparator。然后我们使用排序标签并指定"员工"列表作为源，将"deptComparator"指定为要使用的比较器。然后，按照前面的示例，我们迭代列表并打印员工。从输出中可以看出，这将打印按部门排序的员工列表。
子集标签
子集标签用于获取列表或数组的子集。我们有两种类型的子集标签。在第一个示例中，我们使用recrutimentDecider来获取在招聘部门工作的员工列表(请参阅Employee.java中的getRecruitmentDecider()方法)。
在第二个示例中，我们没有使用任何决策者，而是使用列表中的元素2和3。子集标签包含两个参数"count"和"start"。 "start"确定子集的起点，"count"确定子集的长度。
配置文件
您的struts.xml应该看起来像 −
<?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>
文件 web.xml 应类似于 −
<?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>
右键单击项目名称，然后单击导出 > WAR 文件以创建 War 文件。然后将此 WAR 部署到 Tomcat 的 webapps 目录中。最后，启动 Tomcat 服务器并尝试访问 URL http://localhost:8080/HelloWorldStruts2/employee.action。这将产生以下屏幕 −
struts_control_tags.html
