使用Ajax实现国家-省份-城市三级联动

package com.lym.ajax.servlet; import java.io.IOException; import java.util.List; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.fasterxml.jackson.databind.ObjectMapper; import com.lym.ajax.beans.City; import com.lym.ajax.beans.Country; import com.lym.ajax.beans.Province; import com.lym.ajax.dao.CityDao; import com.lym.ajax.dao.CountryDao; import com.lym.ajax.dao.ProvinceDao; import com.lym.ajax.dao.impl.CityDaoImpl; import com.lym.ajax.dao.impl.CountryDaoImpl; import com.lym.ajax.dao.impl.ProvinceDaoImpl; @WebServlet("/CountryProvinceCityServlet") public class CountryProvinceCityServlet extends HttpServlet { private static final long serialVersionUID = 1L; private static String COUNTRY = "country"; private static String PROVINCE = "province"; private static String CITY = "city"; public CountryProvinceCityServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String method = request.getParameter("method"); if(COUNTRY.equals(method)){ country(request, response); }else if(PROVINCE.equals(method)){ province(request, response); }else if(CITY.equals(method)){ city(request, response); } } //查找国家 protected void country(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { CountryDao dao = new CountryDaoImpl(); List<Country> list = dao.findAll(); request.setAttribute("list", list); request.getRequestDispatcher("/show.jsp").forward(request, response); } //查找省份 protected void province(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String countryId = request.getParameter("countryId"); response.setContentType("text/javascript;charset=utf-8"); ProvinceDao dao = new ProvinceDaoImpl(); List<Province> listProvince = dao.findAll(Integer.parseInt(countryId)); ObjectMapper mapper = new ObjectMapper(); String result = mapper.writeValueAsString(listProvince); //System.out.println(result); response.getWriter().println(result); } //查找城市 protected void city(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String provinceId = request.getParameter("provinceId"); response.setContentType("text/javascript;charset=utf-8"); CityDao dao = new CityDaoImpl(); List<City> listCity = dao.findAll(Integer.parseInt(provinceId)); ObjectMapper mapper = new ObjectMapper(); String result = mapper.writeValueAsString(listCity); //System.out.println(result); response.getWriter().println(result); } }