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简单说明Java的Struts框架中merge标签的使用方法

作者：goldensun　　发布时间：2023-09-17 00:32:26　

标签：Java,Struts

merge标签合并标记需要两个或两个以上的列表作为参数，并把它们合并在一起，如下所示：

<s:merge var="myMergedIterator">
<s:param value="％{myList1}" />
<s:param value="％{myList2}" />
<s:param value="％{myList3}" />
</s:merge>
<s:iterator value="％{#myMergedIterator}">
<s:property />
</s:iterator>

如果有两个列表A和B的值，A1，A2和B1，B2。合并列表，会给出A1，B1，A2，B2。

创建动作类：
首先，让我们创建一个简单的类叫做Employee.java，它看起来像：

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类有两个属性 - name 和 department，我们也有两个员工名单 - employees 和contractors。我们有一个方法叫做getRecruitmentDecider，返回Decider 对象。Decider 实现返回true，如果雇员招聘部门工作，否则返回false。

接下来，让我们创建一个DepartmentComparator 比较Employee对象：

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，部门比较的基础上按字母顺序排列的部门员工进行比较。

创建视图
创建一个文件叫做employee.jsp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>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>

合并标记需要两个或两个以上的列表作为参数。我们需要给合并一个id，这样我们就可以重用它。在这个例子中，我们提供了作为参数传递给员工和承包商的合并标签。然后，我们使用“allemployees”ID合并列表遍历并打印员工的细节。

配置文件
struts.xml中应该像这样：

<?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，应该像这样：

<?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>

右键点击项目名称，并单击 Export > WAR File创建一个WAR文件。然后部署此WAR在Tomcat的webapps目录下。最后，启动Tomcat服务器和尝试访问URL http://localhost:8080/HelloWorldStruts2/employee.action。这会给出以下画面：

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简单说明Java的Struts框架中merge标签的使用方法

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