Struts2的<s:sort>标签使用 java.util.Comparator 来排序列表，这里创建一个Web工程：struts2sorttag，来演示在多个复选框如何设置的默认值，整个项目的结构如下图所示：
在本教程中，将创建6个 Person对象并添加到一个ArrayList，并使用排序标签基于Person属性的ArrayList进行排序。
要使用这个Struts2的<s:sort>标签， 必须了解了java.util.Comparator 是如何工作的
1. Person 对象
创建一个有"firstName”, “lastName” 和 “age”属性的Person对象。
Person.java
package com.xuhuhu.common;
public class Person{
private String firstName;
private String lastName;
private int age;
public Person(String firstName, String lastName, int age) {
super();
this.firstName = firstName;
this.lastName = lastName;
this.age = age;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
2. Comparator
创建2个Comparator类，对Person的“firstName” 和 “age” 属性进行排序。
FirstNameComparator.java
package com.xuhuhu.common;
import java.util.Comparator;
import com.xuhuhu.common.Person;
public class FirstNameComparator implements Comparator<Person> {
public int compare(Person p1, Person p2) {
String firstName1 = p1.getFirstName().toUpperCase();
String firstName2 = p2.getFirstName().toUpperCase();
return firstName1.compareTo(firstName2);
}
}
AgeComparator.java
package com.xuhuhu.common;
import java.util.Comparator;
import com.xuhuhu.common.Person;
public class AgeComparator implements Comparator<Person> {
public int compare(Person p1, Person p2) {
return p1.getAge() - p2.getAge();
}
}
3. 动作-Action
Action类，初始化6个 Person 对象，并把它添加到一个ArrayList。
package com.xuhuhu.common.action;
import java.util.ArrayList;
import java.util.List;
import com.xuhuhu.common.Person;
import com.opensymphony.xwork2.ActionSupport;
public class SortTagAction extends ActionSupport{
private List<Person> persons = new ArrayList<Person>();
public String execute() {
Person p1 = new Person("C-First", "C-Last", 40);
Person p2 = new Person("A-First", "A-Last", 20);
Person p3 = new Person("B-First", "B-Last", 10);
Person p4 = new Person("F-First", "F-Last", 33);
Person p5 = new Person("E-First", "E-Last", 22);
Person p6 = new Person("D-First", "D-Last", 11);
persons.add(p1);
persons.add(p2);
persons.add(p3);
persons.add(p4);
persons.add(p5);
persons.add(p6);
return SUCCESS;
}
public List<Person> getPersons() {
return persons;
}
public void setPersons(List<Person> persons) {
this.persons = persons;
}
}
4. <s:sort>标签示例
JSP页面使用sort标签与“FirstNameComparator”和“AgeComparator”对列表进行排序。
sort.jsp
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head><title>struts2 sort标签示例 - www.xuhuhu.com</title>
</head>
<body>
<h1>Struts 2 Sort标签示例</h1>
<s:bean name="com.xuhuhu.common.FirstNameComparator" var="firstNameComparator" />
<s:bean name="com.xuhuhu.common.AgeComparator" var="ageComparator" />
<table>
<tr>
<td>
1. Display all persons (unsort).
<ol>
<s:iterator value="persons">
<li><s:property value="firstName" />,
<s:property value="lastName" />,
<s:property value="age" />
</li>
</s:iterator>
</ol>
</td>
<td>
2. Display all persons (sort with firstName).
<s:sort comparator="#firstNameComparator" source="persons">
<ol>
<s:iterator>
<li><s:property value="firstName" />,
<s:property value="lastName" />,
<s:property value="age" />
</li>
</s:iterator>
</ol>
</s:sort>
</td>
</tr>
<tr>
<td colspan="2">
3. Display all persons (sort with age).
<s:sort comparator="#ageComparator" source="persons">
<ol>
<s:iterator>
<li><s:property value="firstName" />,
<s:property value="lastName" />,
<s:property value="age" />
</li>
</s:iterator>
</ol>
</s:sort>
</td>
</tr>
</table>
</body>
</html>
5. struts.xml
<?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="default" namespace="/" extends="struts-default"> <action name="sortTagAction" class="com.xuhuhu.common.action.SortTagAction" > <result name="success">pages/sort.jsp</result> </action> </package> </struts>
4. 示例
http://localhost:8080/strut2sorttag/sortTagAction.action
在浏览器打开上面的URL，显示结果如下：
参考
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