Java的Struts框架中append标签与generator标签的使用
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:
<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:
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: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:
<?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:
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。
<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:
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:
<%@ 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:
<?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:
<?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:
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