关闭jvm和spring容器时添加钩子

迷南。 2023-02-14 02:51 24阅读 0赞

平常我们在jvm的时候，如果想做点儿事情怎么办呢，其实很多的框架都为我们预留了钩子(Hook)这种东西，就是为了扩展性，能满足一些需求。先看一下jvm的钩子

public class Test {
    
        public static void main(String[] args) {
            Runtime.getRuntime().addShutdownHook(new Thread(() -> System.out.println("jvm shutdown")));
            int i= 1/0;
            System.out.println("result");
        }
    }

最后输出

Exception in thread "main" java.lang.ArithmeticException: / by zero
    	at Test.main(Test.java:12)
    jvm shutdown

然后我们在spring的容器关闭时，也同样可以加入一个钩子，而这个钩子就是通过registerShutdownHook()方法来实现的。

public void registerShutdownHook() {
            if (this.shutdownHook == null) {
                this.shutdownHook = new Thread("SpringContextShutdownHook") {
                    public void run() {
                        synchronized(AbstractApplicationContext.this.startupShutdownMonitor) {
                            AbstractApplicationContext.this.doClose();
                        }
                    }
                };
                Runtime.getRuntime().addShutdownHook(this.shutdownHook);
            }
    
        }

然后我们来看看这个doClose方法做了什么事情

protected void doClose() {
            if (this.active.get() && this.closed.compareAndSet(false, true)) {
                if (this.logger.isDebugEnabled()) {
                    this.logger.debug("Closing " + this);
                }
    
                LiveBeansView.unregisterApplicationContext(this);
    
                try {
                    this.publishEvent((ApplicationEvent)(new ContextClosedEvent(this)));
                } catch (Throwable var3) {
                    this.logger.warn("Exception thrown from ApplicationListener handling ContextClosedEvent", var3);
                }
    
                if (this.lifecycleProcessor != null) {
                    try {
                        this.lifecycleProcessor.onClose();
                    } catch (Throwable var2) {
                        this.logger.warn("Exception thrown from LifecycleProcessor on context close", var2);
                    }
                }
    
                this.destroyBeans();
                this.closeBeanFactory();
                this.onClose();
                if (this.earlyApplicationListeners != null) {
                    this.applicationListeners.clear();
                    this.applicationListeners.addAll(this.earlyApplicationListeners);
                }
    
                this.active.set(false);
            }
    
        }

可以看到其实是优雅的帮我们注销了所有的bean和注销beanFactory.