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簡(jiǎn)單說(shuō)明Java的Struts框架中merge標(biāo)簽的使用方法

更新時(shí)間：2015年12月04日 08:49:47 投稿：goldensun

這篇文章主要簡(jiǎn)單介紹了Java的Struts框架中merge標(biāo)簽的使用方法,Struts是Java的SSH三大web開發(fā)框架之一,需要的朋友可以參考下

merge標(biāo)簽合并標(biāo)記需要兩個(gè)或兩個(gè)以上的列表作為參數(shù)，并把它們合并在一起，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>

如果有兩個(gè)列表A和B的值，A1，A2和B1，B2。合并列表，會(huì)給出A1，B1，A2，B2。

創(chuàng)建動(dòng)作類：
首先，讓我們創(chuàng)建一個(gè)簡(jiǎn)單的類叫做Employee.java，它看起來(lái)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(gè)屬性 - name 和 department，我們也有兩個(gè)員工名單 - employees 和contractors。我們有一個(gè)方法叫做getRecruitmentDecider，返回Decider 對(duì)象。Decider 實(shí)現(xiàn)返回true，如果雇員招聘部門工作，否則返回false。

接下來(lái)，讓我們創(chuàng)建一個(gè)DepartmentComparator 比較Employee對(duì)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，部門比較的基礎(chǔ)上按字母順序排列的部門員工進(jìn)行比較。

創(chuàng)建視圖
創(chuàng)建一個(gè)文件叫做employee.jsp以下內(nèi)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>

合并標(biāo)記需要兩個(gè)或兩個(gè)以上的列表作為參數(shù)。我們需要給合并一個(gè)id，這樣我們就可以重用它。在這個(gè)例子中，我們提供了作為參數(shù)傳遞給員工和承包商的合并標(biāo)簽。然后，我們使用“allemployees”ID合并列表遍歷并打印員工的細(xì)節(jié)。

配置文件
struts.xml中應(yīng)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(yīng)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(diǎn)擊項(xiàng)目名稱，并單擊 Export > WAR File創(chuàng)建一個(gè)WAR文件。然后部署此WAR在Tomcat的webapps目錄下。最后，啟動(dòng)Tomcat服務(wù)器和嘗試訪問(wèn)URL http://localhost:8080/HelloWorldStruts2/employee.action。這會(huì)給出以下畫面：

201512484907744.jpg (560×264)