解锁新技能《AnnotationConfigApplicationContext@7a8414ea has been closed already》

最近工作过程中遇到了标题中的错误，导致整个项目都不可以访问；原因是我修改了consul的配置，修改过后由于consul监控配置开关是打开着的，所以监控到配置做了修改后会重新创建ApplicationContext对象，并且会将之前的ApplicationContext对象销毁调；由于我在项目启动的时候初始化了一个ApplicationContext全局变量，会在项目中AOP记录访问日志的时候使用，所以每个接口都会报标题中的错误；

一、原因分析

Consul配置监控类ConfigWatch监控consul配置中心的配置变动，如果配置有变动会触发RefreshEvent事件

	@Timed("consul.watch-config-keys")public void watchConfigKeyValues() {if (!this.running.get()) {return;}for (String context : this.consulIndexes.keySet()) {//********RefreshEventData data = new RefreshEventData(context, currentIndex, newIndex);//配置有变动，触发RefreshEvent事件this.publisher.publishEvent(new RefreshEvent(this, data, data.toString()));//*****}this.firstTime = false;}

RefreshEventListener监听器监听RefreshEvent事件，并创建新的ApplicationContext对象，销毁原来的ApplicationContext对象

	@Overridepublic void onApplicationEvent(ApplicationEvent event) {if (event instanceof ApplicationReadyEvent) {handle((ApplicationReadyEvent) event);}else if (event instanceof RefreshEvent) {//监听RefreshEvent事件handle((RefreshEvent) event);}}public void handle(ApplicationReadyEvent event) {this.ready.compareAndSet(false, true);}public void handle(RefreshEvent event) {if (this.ready.get()) { // don't handle events before app is readylog.debug("Event received " + event.getEventDesc());// 触发ContextRefresher类的refresh方法来创建ApplicationContext对象Set<String> keys = this.refresh.refresh();log.info("Refresh keys changed: " + keys);}}

ContextRefresher类新建ApplicationContext并发送EnvironmentChangeEvent事件

	public synchronized Set<String> refresh() {Set<String> keys = refreshEnvironment();this.scope.refreshAll();return keys;}public synchronized Set<String> refreshEnvironment() {Map<String, Object> before = extract(this.context.getEnvironment().getPropertySources());updateEnvironment();Set<String> keys = changes(before, extract(this.context.getEnvironment().getPropertySources())).keySet();//触发EnvironmentChangeEvent事件，可以在此事件的监听器来修改重建后的ApplicationContextthis.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));return keys;}
//此方法的实现(LegacyContextRefresher.updateEnvironment)是真正用来新建ApplicationContext和销毁原来ApplicationContext的
protected abstract void updateEnvironment();

LegacyContextRefresher.updateEnvironment实现

public class LegacyContextRefresher extends ContextRefresher {@Deprecatedpublic LegacyContextRefresher(ConfigurableApplicationContext context, RefreshScope scope) {super(context, scope);}public LegacyContextRefresher(ConfigurableApplicationContext context, RefreshScope scope,RefreshAutoConfiguration.RefreshProperties properties) {super(context, scope, properties);}@Overrideprotected void updateEnvironment() {addConfigFilesToEnvironment();}/* For testing. */ ConfigurableApplicationContext addConfigFilesToEnvironment() {ConfigurableApplicationContext capture = null;try {//*****************省略*******************SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class).bannerMode(Banner.Mode.OFF).web(WebApplicationType.NONE).environment(environment);// Just the listeners that affect the environment (e.g. excluding logging// listener because it has side effects)builder.application().setListeners(Arrays.asList(new BootstrapApplicationListener(), new BootstrapConfigFileApplicationListener()));// 新建ApplicationContext对象，实际会进入org.springframework.boot.builder.SpringApplicationBuilder#run方法创建；capture = builder.run();//*************省略**********************}finally {ConfigurableApplicationContext closeable = capture;while (closeable != null) {try {//closeable.close();}catch (Exception e) {// Ignore;}if (closeable.getParent() instanceof ConfigurableApplicationContext) {closeable = (ConfigurableApplicationContext) closeable.getParent();}else {break;}}}return capture;}}

上述builder.run方法会进入org.springframework.boot.builder.SpringApplicationBuilder#run最终是在org.springframework.boot.SpringApplication#run(java.lang.String…)方法中创建：

二、解决方案

在原因分析中我们知道新建ApplicationContext后会发送EnvironmentChangeEvent事件，而EnvironmentChangeEvent事件会接收一个ApplicationContext作为参数，我们的解决方案就是监听EnvironmentChangeEvent事件，修改定义的全局变量；

方案一：使用@RabbitListener注解监听EnvironmentChangeEvent事件

    @EventListenerpublic void handler(EnvironmentChangeEvent event){ApplicationContext context = (ApplicationContext) event.getSource();//修改定义的全局ApplicationContext对象IOCContext.setCONTEXT(context);System.out.println(event.getSource());}

此方案适用于具体项目之中，如果想用在springboot脚手架类SDK中，这种方案就行不通了；

方案二：定义实现ApplicationListener监听器接口类

public class EnvironmentChangeApplicationListener implements ApplicationListener<EnvironmentChangeEvent> {@Overridepublic void onApplicationEvent(EnvironmentChangeEvent event) {Object source = event.getSource();if (Objects.isNull(source) || !(source instanceof ApplicationContext)) {return;}IOCContext.setCONTEXT((ApplicationContext) source);}
}