Java的Struts框架中append标签与generator标签的使用

时间:2021-11-06 04:19:55

append 标签:
这些append标签需要两个或两个以上的列表作为参数,并追加它们放在一起,如下图所示:

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<s:append var="myAppendIterator">
   <s:param value="%{myList1}" />
   <s:param value="%{myList2}" />
   <s:param value="%{myList3}" />
</s:append>
<s:iterator value="%{#myAppendIterator}">
   <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,会给你的A1,A2,B1,B2,而append 名单,会有A1,A2,B1,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:

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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:

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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:

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<%@ 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:append id="allemployees">
   <s:param value="employees" />
   <s:param value="contractors" />
  </s:append >
  <s:iterator value="allemployees">
   <s:property value="name"/>,
   <s:property value="department"/><br/>
  </s:iterator>
</body>
</html>

append标签需要两个或两个以上列出作为参数。我们需要给予追加一个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附加标签。然后,我们使用“allemployees”ID遍历附加列表和打印员工的细节。

配置文件
struts.xml中应该像这样:

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<?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:

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<?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:

Java的Struts框架中append标签与generator标签的使用

generator 标签:
generator标签生成一个迭代器的基础上提供val属性。以下generator标签生成一个迭代器,并使用迭代器标签打印出来。

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<s:generator val="%{'aaa,bbb,ccc,ddd,eee'}">
 <s:iterator>
   <s:property /><br/>
 </s:iterator>
</s:generator>

我们经常遇到的一些情况,必须创建列表或数组上遍历列表。可以创建列表或数组使用scriptlet或者可以使用generator 标签。 tag.

创建action类:

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package com.yiibai.struts2;
 
public class HelloWorldAction{
  private String name;
 
  public String execute() throws Exception {
   return "success";
  }
  
  public String getName() {
   return name;
  }
 
  public void setName(String name) {
   this.name = name;
  }
}

创建视图
下列 helloWorld.jsp 展示使用generator 标记:

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<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Hello World</title>
</head>
<body>
 
<h2>Example of Generator Tag</h2>
<h3>The colours of rainbow:</h3>
 
<s:generator val="%{'Violet,Indigo,Blue,
     Green,Yellow,Orange,Red '}" count="7"
     separator=",">
  <s:iterator>
   <s:property /><br/>
  </s:iterator>
</s:generator>
 
</body>
</html>

在这里,我们创建一个generator 标签,我们要求它解析的字符串,其中包含逗号分隔的列表,形成了彩虹的颜色。我们告诉发电机标签,分隔符是“,”我们希望所有七个值在列表中。如果我们只关心前三个值,然后我们会设置计数至3。发电机标记在体内,我们使用了迭代器去通过由generator 标记创建的值的打印属性的值。

配置文件
struts.xml 应该像这样:

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<?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="hello"
      class="com.yiibai.struts2.HelloWorldAction"
      method="execute">
      <result name="success">/HelloWorld.jsp</result>
   </action>
 
  </package>
</struts>

web.xml 应该像这样:

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<?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/hello.action。这会给出以下画面:

Java的Struts框架中append标签与generator标签的使用