In some cases, you may have this requirement: in a Spring/SpringMVC project, when Spring/SpringMVC is started, you need to execute a method to complete certain events (such as creating a sitemap, such as subscribing from Redis Server, etc.), at this time, the event callback mechanism provided by the Tomcat/Servlet container can be used to complete, but there is a problem: the Annotation provided by Spring cannot be used. The solution is:
- /*
- * To change this license header, choose License Headers in Project Properties.
- * To change this template file, choose Tools | Templates
- * and open the template in the editor.
- */
- package com.storezhang.web;
- import com.storezhang.util.TimeUtils;
- import com.storezhang.video.util.SiteMapUtils;
- import java.util.Timer;
- import java.util.TimerTask;
- import org.springframework.beans.factory.annotation.Autowired;
- import org.springframework.context.ApplicationListener;
- import org.springframework.context.event.ContextRefreshedEvent;
- import org.springframework.stereotype.Service;
- /**
- * start the listener
- *
- * @author Storezhang
- */
- @Service
- public class StartupListener implements ApplicationListener<ContextRefreshedEvent> {
- @Autowired
- private SiteMapUtils sites;
- @Override
- public void onApplicationEvent(ContextRefreshedEvent evt) {
- if (evt.getApplicationContext().getParent() == null) {
- createSitemap();
- }
- }
- private void createSitemap() {
- Timer timer = new Timer("createSitemap", true);
- timer.schedule(new TimerTask() {
- @Override
- public void run() {
- System.out.println("--->Create sitemap...");
- sites.createSiteMap();
- System.out.println("--->Success create sitemap...");
- }
- }, 1 * TimeUtils.MIN);
- }
- }
后续研究:
applicationontext和使用MVC之后的webApplicationontext会两次调用上面的方法,如何区分这个两种容器呢?
但是这个时候,会存在一个问题,在web 项目中(spring mvc),系统会存在两个容器,一个是root application context ,另一个就是我们自己的 projectName-servlet context(作为root application context的子容器)。
这种情况下,就会造成onApplicationEvent方法被执行两次。为了避免上面提到的问题,我们可以只在root application context初始化完成后调用逻辑代码,其他的容器的初始化完成,则不做任何处理,修改后代码
如下:
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
if(event.getApplicationContext().getParent() == null){//root application context 没有parent,他就是老大.
//需要执行的逻辑代码,当spring容器初始化完成后就会执行该方法。
}
}