1.需求：很多時候，在一個 web 專案啟動的時候，我們都要【初始化很多系統引數，比如讀取配置檔案】，或者初始化資料庫表…

2.解決方法：實現【 ServletContextListener】 介面
2.1 把實現了ServletContextListener 的類配置到【 web.xml】 檔案中

<?xml version="1.0" encoding="UTF-8"?>  
<web-app version="2.5"   
    xmlns="http://java.sun.com/xml/ns/javaee"   
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 
   
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  
  <display-name></display-name>   
  <welcome-file-list>  
    <welcome-file>index.jsp</welcome-file>  
      </welcome-file-list>  
      <listener>
 
  
        <listener-class>com.chinaso.init.StartInit</listener-class>  
      </listener>  
      <filter>  
        <filter-name>struts2</filter-name>  
        <filter-class>  
            org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter  
        </filter-class
 
>  
      </filter>  
      <filter-mapping>  
        <filter-name>struts2</filter-name>  
        <url-pattern>/*</url-pattern>  
      </filter-mapping>  
      </web-app>  

2.2.加入自己的實現邏輯

public class StartInit implements ServletContextListener {  
    static final Logger logger = LoggerFactory.getLogger(StartInit.class);  
    // 系統初始化執行方法  
    public void contextDestroyed(ServletContextEvent e) {  
        logger.info("系統停止...");  
    }  

    public void contextInitialized(ServletContextEvent e) {  
        logger.info("系統初始化開始...");  

            // 獲取專案根目錄  
            String root_path  = e.getServletContext().getRealPath("/");  
            logger.info("application path : {}",root_path);  

            // 初始化 ConfigFactorty  
            ConfigFactory.init(root_path);  
            // 初始化資料鏈接資訊  
            DBManager.init();  
            // 初始化定時統計任務  
            TaskManager.init();  
            // 初始化使用者資訊查詢位置  
            UserInfo.init();  

            logger.info("系統初始化結束...");  
        }  

    }  

3.使用springboot時的資料初始化

首先要配置掃描@Component

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.boot.web.support.SpringBootServletInitializer;
import org.springframework.scheduling.annotation.EnableScheduling;


/**
 * 啟動類
 *
 */
@SpringBootApplication
@EnableScheduling    //@EnableScheduling （執行定時器任務） @Scheduled的任務並後臺執行。
@ServletComponentScan    //掃描過（執行過濾器）濾器 註解
//@ComponentScan(basePackages={"util}) // 掃描該包路徑下的所有spring元件
public class Application extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
            builder.sources(this.getClass());
            return super.configure(builder);

    }
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

其次新增初始化類，實現ApplicationContextAware

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import stock.simulator.trader.web.quartz.QuartzJobManager;

/**
 * Created by dzd-technology01 on 2017/9/25.
 */
@Component
public class ApplicationContextUtil implements ApplicationContextAware {
    private static ApplicationContext applicationContext;

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        ApplicationContextUtil.applicationContext = applicationContext;
        // ***---初始化操作---***
        QuartzJobManager.I.init();
    }

    public static Object getBean(String beanName){
        return applicationContext.getBean(beanName);
    }


    //通過class獲取Bean.
    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    //通過name,以及Clazz返回指定的Bean
    public static <T> T getBean(String name,Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }
}

public class QuartzJobManager {

    public static QuartzJobManager I = new QuartzJobManager();

    public QuartzJobManager() {
    }

    public void init() {
        // do something...
    }

}