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简单说明Java的Struts框架中merge标签的使用方法

程序员文章站 2024-03-07 15:33:21
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:

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:

简单说明Java的Struts框架中merge标签的使用方法