如何让spring mvc web应用启动时就执行特定处理

Asp.Net的应用中通过根目录下的Global.asax，在Application_Start方法中做一些初始化操作，比如：预先加载缓存项对网站热点数据进行预热，获取一些远程的配置信息等等。

Spring-MVC的应用中，要实现类似的功能，主要是通过实现下面这些接口（任选一，至少一个即可）

一、ApplicationContextAware接口

package org.springframework.context;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.Aware;
import org.springframework.context.ApplicationContext;

public interface ApplicationContextAware extends Aware {
    void setApplicationContext(ApplicationContext var1) throws BeansException;
}

二、ServletContextAware 接口

package org.springframework.web.context;

import javax.servlet.ServletContext;
import org.springframework.beans.factory.Aware;

public interface ServletContextAware extends Aware {
    void setServletContext(ServletContext var1);
}

三、InitializingBean 接口

package org.springframework.beans.factory;

public interface InitializingBean {
    void afterPropertiesSet() throws Exception;
}

四、ApplicationListener<ApplicationEvent> 接口

package org.springframework.context;

import java.util.EventListener;
import org.springframework.context.ApplicationEvent;

public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
    void onApplicationEvent(E var1);
}

示例程序：

package test.web.listener;

import org.apache.logging.log4j.*;
import org.springframework.beans.*;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.*;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;
import org.springframework.web.context.ServletContextAware;
import javax.servlet.ServletContext;

@Component
public class StartupListener implements ApplicationContextAware, ServletContextAware,
        InitializingBean, ApplicationListener<ContextRefreshedEvent> {

    protected Logger logger = LogManager.getLogger();

    @Override
    public void setApplicationContext(ApplicationContext ctx) throws BeansException {
        logger.info("1 => StartupListener.setApplicationContext");
    }

    @Override
    public void setServletContext(ServletContext context) {
        logger.info("2 => StartupListener.setServletContext");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        logger.info("3 => StartupListener.afterPropertiesSet");
    }

    @Override
    public void onApplicationEvent(ContextRefreshedEvent evt) {
        logger.info("4.1 => MyApplicationListener.onApplicationEvent");
        if (evt.getApplicationContext().getParent() == null) {
            logger.info("4.2 => MyApplicationListener.onApplicationEvent");
        }
    }

}

运行时，输出的顺序如下：

1 => StartupListener.setApplicationContext
2 => StartupListener.setServletContext
3 => StartupListener.afterPropertiesSet
4.1 => MyApplicationListener.onApplicationEvent
4.2 => MyApplicationListener.onApplicationEvent
4.1 => MyApplicationListener.onApplicationEvent

注意：onApplicationEvent方法会触发多次，初始化这种事情，越早越好，建议在setApplicationContext方法中处理。