如何在项目启动的时候做一些业务处理 （实现ServletContextListener）

业务场景：如果我们项目中有一些常用属性表，可能我们会经常用到。这时候就可以在项目启动时，把数据放到静态map里，在用的时候就不用查数据了，提高程序效率，简化了代码。

实现方案：

1。创建一个ServletContextListener的实现类

package com.travel.util;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import org.springframework.context.ApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;import com.travel.service.FlighCondRecordService;public class MyListener implements ServletContextListener {@Overridepublic void contextDestroyed(ServletContextEvent arg0) {// TODO Auto-generated method stub}@Overridepublic void contextInitialized(ServletContextEvent sce) {try {  //项目启动时加载，需配置对应的web.xml            ApplicationContext context = WebApplicationContextUtils.getRequiredWebApplicationContext(sce.getServletContext());              Object bean = context.getBean( "flighCondRecordServiceImpl" );              FlighCondRecordService fs =  (FlighCondRecordService)bean;            fs.saveAirMap();      } catch (Exception e) {              e.printStackTrace();        }  }}

在web.xml中添加listener

<listener><listener-class>com.travel.util.MyListener</listener-class>   </listener>

@Overridepublic void saveAirMap() {if (CacheAir.cacheAirport.isEmpty()) {List<FlightCommAttr> findType = flightCommAttrDao.findType("airport");for (int i = 0; i < findType.size(); i++) {CacheAir.cacheAirport.put(findType.get(i).getCode(), findType.get(i).getCodeDesc());}}if (CacheAir.cacheAirCompany.isEmpty()) {List<FlightCommAttr> airCompany = flightCommAttrDao.findType("airCompany");for (int i = 0; i < airCompany.size(); i++) {CacheAir.cacheAirCompany.put(airCompany.get(i).getCode(),airCompany.get(i).getCodeDesc());}}if (CacheAir.cacheFlightTime.isEmpty()) {List<FlightCommAttr> flightTime = flightCommAttrDao.findType("flightTime");for (int i = 0; i < flightTime.size(); i++) {CacheAir.cacheFlightTime.put(flightTime.get(i).getCode(),flightTime.get(i).getCodeDesc());}}if (CacheAir.cacheCarbinRank.isEmpty()) {List<FlightCommAttr> carbinRank = flightCommAttrDao.findType("carbinRank");for (int i = 0; i < carbinRank.size(); i++) {CacheAir.cacheCarbinRank.put(carbinRank.get(i).getCode(),carbinRank.get(i).getCodeDesc());}}if (CacheAir.cacheCity.isEmpty()) {List<FlightCommAttr> city = flightCommAttrDao.findType("cityCN");for (int i = 0; i < city.size(); i++) {CacheAir.cacheCity.put(city.get(i).getCode(),city.get(i).getCodeDesc());}}}

public  class CacheAir {public static final  Map<String,String> cacheAirport =new  LinkedHashMap<String,String>();public static final  Map<String,String> cacheAirCompany=new  LinkedHashMap<String,String>();public static final  Map<String,String> cacheFlightTime=new  LinkedHashMap<String,String>();public static final  Map<String,String> cacheCarbinRank=new  LinkedHashMap<String,String>();public static final  Map<String,String> cacheCity=new  LinkedHashMap<String,String>();}