select多选框省市县三级级联

通过“模块化开发”的方式来实现三级级联：

test.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html><head><title>Insert title here</title><script type="text/javascript" src="./js/jquery-1.8.3.min.js"></script><script type="text/javascript" src="./js/json2.js"></script><script type="text/javascript">var obj={url:"./AreaServlet",dataType:"text",success:function(data){data=JSON.parse(data);var options ="<option value=''>--请选择--</option>";for(var i=0;i<data.length;i++){var obj = data[i];options = options+"<option value="+obj.code+">"+obj.name+"</option>";}$("#province").empty();$("#province").append(options);}};$.ajax(obj);function getCity(){var parentCode=$("#province").val();if(parentCode==""){//加此判断是因为默认从AreaService传入到AreaDao的parentCode就为"",即默认是省选项，因此通过本判断来阻止该现象的发生，同时当省选项变化为"--请选择--"时，通过该判断可以清空市县选项框。$("#city").empty();$("#county").empty();$("#city").append("<option value=''>--请选择--</option>");$("#county").append("<option value=''>--请选择--</option>");return;}var obj={	url:"./AreaServlet?parent_code="+parentCode,dataType:"text",success:function(data){data=JSON.parse(data);var options ="<option value=''>--请选择--</option>";for(var i=0;i<data.length;i++){var obj = data[i];options = options+"<option value="+obj.code+">"+obj.name+"</option>";}$("#city").empty();$("#county").empty();$("#city").append(options);$("#county").append("<option value=''>--请选择--</option>");}};$.ajax(obj);}function getCounty(){var parentCode=$("#city").val();if(parentCode==""){//该判断是当市级选项卡改变时，自动将县级选项卡清空$("#county").empty();$("#county").append("<option value=''>--请选择--</option>");return;}var obj={url:"./AreaServlet?parent_code="+parentCode,dataType:"text",success:function(data){data=JSON.parse(data);var options ="<option value=''>--请选择--</option>";for(var i=0;i<data.length;i++){var obj = data[i];options = options+"<option value="+obj.code+">"+obj.name+"</option>";}$("#county").empty();$("#county").append(options);}};$.ajax(obj);};</script>	</head><body><select id="province" onchange="getCity()"><option value="">--请选择--</option></select><select id="city" onchange="getCounty()"><option value="">--请选择--</option></select><select id="county"><option value="">--请选择--</option></select></body>
</html>

AreaServlet:

package area.servlet;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.google.gson.Gson;import area.imp.IAreaService;
import area.service.AreaService;public class AreaServlet extends HttpServlet {private static final long serialVersionUID = 1L;private IAreaService areaService = new AreaService();protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/plain; charset=UTF-8");String parentCode = request.getParameter("parent_code");String json = new Gson().toJson(areaService.select(parentCode));System.out.println(json);PrintWriter out = response.getWriter();out.write(json);out.flush();out.close();}}

AreaService:

package area.service;import java.util.List;import com.jd.vo.Area;import area.dao.AreaDao;
import area.imp.IAreaDao;
import area.imp.IAreaService;public class AreaService implements IAreaService {private IAreaDao areaDao = new AreaDao();@Overridepublic List<Area> select(String parentCode) {if(parentCode==null) {//该判断是让parentCode为空时让null转换为"",从而符合数据库表中的查询规范parentCode="";}return areaDao.select(parentCode);}
}

AreaDao:

package area.dao;import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;import com.jd.tool.db.DBLink;
import com.jd.tool.db.IRowMapper;
import com.jd.vo.Area;import area.imp.IAreaDao;public class AreaDao implements IAreaDao {@Overridepublic List<Area> select(String parentCode) {String sql = "select * from area where parent_code='"+parentCode+"'";final List<Area>LIST = new ArrayList<Area>();new DBLink().select(sql,new IRowMapper(){public void rowMapper(ResultSet rs) {try {while(rs.next()) {LIST.add( new Area(rs.getString("id"), rs.getString("code"), rs.getString("name") , rs.getString("parent_code") ));}} catch (SQLException e) {e.printStackTrace();}}});return LIST;}
}

IAreaService:

package area.imp;import java.util.List;import com.jd.vo.Area;public interface IAreaService {List<Area> select(String parentCode);
}

IAreaDao:

package area.imp;import java.util.List;import com.jd.vo.Area;public interface IAreaDao {List<Area> select(String parentCode);
}