前端介绍完了，我们回到后端进行介绍，当然了，你也可以忽略本节，因为不是所用的关联数据都通过springMVC这种方法获取，那么先预览一下代码吧！
package com.honzh.spring.controller; import java.util.ArrayList; import java.util.List; import javax.servlet.http.HttpServletResponse; import org.apache.log4j.Logger; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import com.honzh.biz.database.entity.City; import com.honzh.biz.database.entity.Option; import com.honzh.biz.database.entity.Provincial; import com.honzh.common.util.JsonUtil; import com.honzh.spring.service.CityService; import com.honzh.spring.service.ProvincialService; @Controller @RequestMapping(value = "/procity") public class ProcityController extends BaseController { private static Logger logger = Logger.getLogger(ProcityController.class); /** * 当传递city_code，则表明下拉框要被选中，否则不选中 */ @RequestMapping("") public void index(@RequestParam(value = "city_code", required = false) String city_code, @RequestParam(value = "pro_code", required = false) String pro_code, HttpServletResponse response) { try { logger.debug("获取所在地区" + city_code + ", 省" + pro_code); // 如果pro_code为””，则表明要获取城市菜单，否则获取市级菜单 if (!pro_code.equals("")) { Integer pro_id = ProvincialService.getInstance().getByProvincialcode(pro_code).getId(); List<City> citys = CityService.getInstance().getCitysByProvincialId(pro_id); List<Option> coptions = new ArrayList<Option>(citys.size()); for (City city : citys) { Option coption = new Option(); coption.setId(city.getId()); coption.setName(city.getCname()); coption.setValue(city.getCode()); // 市级菜单被选中 if (city_code != null && !city_code.equals("")) { if (city.getCode().equals(city_code)) { coption.setSelected("selected"); } } coptions.add(coption); } renderJson(response, coptions); } else { List<Provincial> provincials = ProvincialService.getInstance().getProvincials(); // 转换成标准的option属性（name,value,selected） List<Option> options = new ArrayList<Option>(provincials.size()); // 被选中的省市 // 则说明是展示页面，此时需要为省级菜单和市级菜单设置选择项 if (city_code != null && !city_code.equals("")) { Provincial selected_provincial = ProvincialService.getInstance().getProvincialByCitycode(city_code); pro_code = selected_provincial.getProcode(); } else { pro_code = provincials.get(0) == null ? "" : provincials.get(0).getProcode(); } for (Provincial provincial : provincials) { Option option = new Option(); option.setId(provincial.getId()); option.setName(provincial.getProname()); option.setValue(provincial.getProcode()); if (!pro_code.equals("") && provincial.getProcode().equals(pro_code)) { option.setSelected("selected"); } options.add(option); } renderJson(response, JsonUtil.toJson(options)); } } catch (Exception e) { logger.error(e.getMessage()); logger.error(e.getMessage(), e); renderJson(response, null); } } }