Spring初始化总结ApplicationListener

我们在使用Spring开发的时候，很多的时候都需要在bean初始化之前，预先处理一些基础性东西，如从配置服务器上获取服务启动配置参数，但是我们往往是在初始化类上使用@postConstruct或是init-method="init"。但是这两种方法，我们很难控制执行的先后顺序，为了控制绝对的初始化顺序，所以我们需要使用ApplicationListener，这个类可以使用org.springframework.context.event包下面的所有事件，我们可以使用ContextRefreshedEvent来保证绝对的第一个执行

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

@Component
public class ApplicationListenerImp implements ApplicationListener<ContextRefreshedEvent> {

	@Override
	public void onApplicationEvent(ContextRefreshedEvent arg0) {
		System.out.println("aaa");
		try {
			Thread.sleep(3000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("bbb");
	}

}

import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.senyint.framework.common.ApplicationContextUtil;
import com.senyint.framework.config.SpringContext;
import com.senyint.framework.controller.DemoController;
import com.senyint.framework.controller.DyController;

public class Demo5 {

	public static void main(String[] args) {
		AnnotationConfigApplicationContext ac=ApplicationContextUtil.getContext();
		ac.register(DyController.class);
		//System.out.println(ac.containsBean("applicationListenerImp"));
		/*
		 * DemoService demoService=SpringContext.getBean(DemoService.class);
		 * System.out.println(demoService.getInfo()); ApplicationContext
		 * context=SpringContext.getContext(); DemoService
		 * demoService1=context.getBean(DemoService.class);
		 * System.out.println(demoService1.getInfo());
		 */
		System.out.println(ac.containsBean("demoController"));
		ac.removeBeanDefinition("demoController");
		System.out.println(ac.containsBean("demoController"));
		testDyBean(ac);
	}
	
	public static void testDyBean(AnnotationConfigApplicationContext ac) {
		System.out.println(ac.containsBean("dyController"));
		DyController dy=ac.getBean(DyController.class);
		System.out.println(dy.getInfo());
		
	}

}

log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
aaa
bbb
true
false
true
this is a test

下面是执行结果，是不是很明显。