doubleselect算是Struts2中稍微复杂点的表单标签, 尤其官方示例比较简单, 没有太大的实用价值.
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<s:doubleselect label="doubleselect test2" name="menu" list="#{'fruit':'Nice Fruits', 'other':'Other Dishes'}" doubleName="dishes" doubleList="top == 'fruit' ? {'apple', 'orange'} : {'monkey', 'chicken'}" />
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从这个官方示例中可以看到基本用法, list开头的代表的是第一级下拉框的属性, doubleList开头的则是第二级下拉框. 与select标签的属性基本是对应的.
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在实际应用中, 我们比较关注的就是list和doubleList这两个属性了, list是存放的第一级下拉框的数据集合, 比如List<FatherBean>, 而doubleList就可以用Map<String, List<SonBean>>来存储, 其中map的键名String与第一级下拉框相关联.
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现在来展示一个我写的示例：
先写两个javaBean，一般情况下是跟数据库的表相关联的：
package com.student.bean;
public class Province {
int id;
String name;
//set和get方法
}
package com.student.bean;
public class City {
int
id;
String name;
int
provinceId;
//set和get方法
}
再来写Action，用来往web页面发送数据：
package com.student.action;
import java.util.ArrayList;
import java.util.HashMap;
import
java.util.List;
import java.util.Map;
import
com.opensymphony.xwork2.ActionSupport;
import
com.student.bean.Province;
import com.student.bean.City;
public class DoubleSelectAction extends ActionSupport {
private List<Province>
provinceList;
private Map<Integer, List<City>>
cityMap;
public
List<Province> getProvinceList() {
return
provinceList;
}
public void setProvinceList(List<Province> provinceList)
{
this.provinceList = provinceList;
}
public Map<Integer, List<City>> getCityMap()
{
return cityMap;
}
public void setCityMap(Map<Integer, List<City>> cityMap)
{
this.cityMap = cityMap;
}
public String execute() throws Exception
{
provinceList= new
ArrayList<Province>();
Province
province;
province = new
Province();
province.setId(1);
province.setName("山西省");
provinceList.add(province);
province =
new
Province();
province.setId(2);
province.setName("陕西省");
provinceList.add(province);
province =
new
Province();
province.setId(3);
province.setName("河南省");
provinceList.add(province);
cityMap = new HashMap<Integer, List<City>>();
List<City> cityList = new
ArrayList<City>();
City city;
city = new
City();
city.setId(1);
city.setName("太原市");
city.setProvinceId(1);
cityList.add(city);
city= new
City();
city.setId(2);
city.setName("大同市");
city.setProvinceId(1);
cityList.add(city);
city= new
City();
city.setId(3);
city.setName("长治市");
city.setProvinceId(1);
cityList.add(city);
cityMap.put(1, cityList);
cityList =
new
ArrayList<City>();
city= new
City();
city.setId(4);
city.setName("西安市");
city.setProvinceId(2);
cityList.add(city);
city= new
City();
city.setId(5);
city.setName("汉中市");
city.setProvinceId(2);
cityList.add(city);
city= new
City();
city.setId(6);
city.setName("咸阳市");
city.setProvinceId(2);
cityList.add(city);
cityMap.put(2,
cityList);
cityList = new
ArrayList<City>();
city= new
City();
city.setId(7);
city.setName("郑州市");
city.setProvinceId(3);
cityList.add(city);
city= new
City();
city.setId(8);
city.setName("开封市");
city.setProvinceId(3);
cityList.add(city);
city= new
City();
city.setId(8);
city.setName("洛阳市");
city.setProvinceId(3);
cityList.add(city);
cityMap.put(3, cityList);
return
SUCCESS;
}
}
现在写配置文件：
<action name="doubleSelect"
class="com.student.action.DoubleSelectAction">
<result
name="success">/tagsDoubleSelect.jsp</result>
</action>
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最后写显示级联下拉菜单的web页面：
<%@ page language="java" contentType="text/html;
charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s"
uri="/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01
Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta
http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<title>struts2级联下拉菜单示例</title>
</head>
<body>
<s:form name="f1">
<s:doubleselect
list="provinceList" listKey="id"
listValue="name"
doubleName="cityId"
doubleList="cityMap.get(top.id)"
doubleListKey="id"
doubleListValue="name"/>
</s:form>
</body>
</html>
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此处要注意的是top的用法，top代表的就是list当前选中的对象, 所以top.id对应的就是当前选中的Province对象中的ID, cityMap.get(top.id)即根据当前选中的Province对象中的ID来取出第二级下拉框的数据集合
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