Spring中的Lifecycle接口使用与源码分析

public interface Lifecycle {
	    /**
     * 启动当前组件，如果组件已经在运行，不应该抛出异常，这样将开始信号传播到应用的所有组件中去。
     */
	void start();
	    /**
     * 通常以同步方式停止该组件，当该方法执行完成后，该组件会被完全停止。当需要异步停止行为时，考虑实现SmartLifecycle和它的 stop(Runnable) 方法变体。 
	 注意，此停止通知在销毁前不能保证到达:
　　　　在常规关闭时，{@code Lifecycle} bean将首先收到一个停止通知，然后才传播常规销毁回调;
　　　　在上下文的生命周期内的刷新或中止时，只调用销毁方法
　　　　对于容器，这将把停止信号传播到应用的所有组件
     */
	void stop();
	    /**
      *  检查此组件是否正在运行。
      *  1. 只有该方法返回false时，start方法才会被执行。
      *  2. 只有该方法返回true时，stop(Runnable callback)或stop()方法才会被执行。
      */
	boolean isRunning();
}

package com.morris.spring.demo.lifecycle;
import org.springframework.context.Lifecycle;
/**
 * 自定义Lifecycle
 */
public class MyLifecycle implements Lifecycle {
	private boolean isRunning;
	@Override
	public void start() {
		System.out.println("MyLifecycle start");
		isRunning = true;
	}
	@Override
	public void stop() {
		System.out.println("MyLifecycle stop");
		isRunning = false;
	}
	@Override
	public boolean isRunning() {
		return isRunning;
	}
}

public class LifecycleDemo {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
		applicationContext.register(MyLifecycle.class);
		applicationContext.refresh();
	}
}

public class LifecycleDemo {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
		applicationContext.register(MyLifecycle.class);
		applicationContext.refresh();
		applicationContext.start();
		applicationContext.stop();
	}
}

DEBUG main DefaultLifecycleProcessor:356 - Starting beans in phase 0
MyLifecycle start
DEBUG main DefaultLifecycleProcessor:188 - Successfully started bean 'myLifecycle'
DEBUG main DefaultLifecycleProcessor:369 - Stopping beans in phase 0
MyLifecycle stop
DEBUG main DefaultLifecycleProcessor:253 - Successfully stopped bean 'myLifecycle'

public interface SmartLifecycle extends Lifecycle, Phased {
	int DEFAULT_PHASE = Integer.MAX_VALUE;
	/**
      * 如果该`Lifecycle`类所在的上下文在调用`refresh`时，希望能够自己自动进行回调，则返回`true`* ,
      * false的值表明组件打算通过显式的start()调用来启动，类似于普通的Lifecycle实现。
     */
	default boolean isAutoStartup() {
		return true;
	}
	default void stop(Runnable callback) {
		stop();
		callback.run();
	}
	@Override
	default int getPhase() {
		return DEFAULT_PHASE;
	}
}

package com.morris.spring.demo.lifecycle;
import org.springframework.context.SmartLifecycle;
/**
 * 自定义SmartLifecycle
 */
public class MySmartLifecycle implements SmartLifecycle {
	private boolean isRunning;
	@Override
	public void start() {
		System.out.println("MyLifecycle start");
		isRunning = true;
	}
	@Override
	public void stop() {
		System.out.println("MyLifecycle stop");
		isRunning = false;
	}
	@Override
	public boolean isRunning() {
		return isRunning;
	}
}

package com.morris.spring.demo.lifecycle;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
/**
 * 演示SmartLifecycle
 */
public class SmartLifecycleDemo {
	public static void main(String[] args) {
		AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
		applicationContext.register(MySmartLifecycle.class);
		applicationContext.refresh();
	}
}

DEBUG main DefaultListableBeanFactory:228 - Creating shared instance of singleton bean 'mySmartLifecycle'
DEBUG main DefaultLifecycleProcessor:357 - Starting beans in phase 2147483647
MyLifecycle start
DEBUG main DefaultLifecycleProcessor:189 - Successfully started bean 'mySmartLifecycle'

public void start() {
	// 获取DefaultLifecycleProcessor
	/**
		 * @see DefaultLifecycleProcessor#start()
		 */
	getLifecycleProcessor().start();
	publishEvent(new ContextStartedEvent(this));
}

public void start() {
	startBeans(false);
	this.running = true;
}

protected void finishRefresh() {
	// Clear context-level resource caches (such as ASM metadata from scanning).
	clearResourceCaches();
	// Initialize lifecycle processor for this context.
	// 注入DefaultLifecycleProcessor
	initLifecycleProcessor();
	// Propagate refresh to lifecycle processor first.
	getLifecycleProcessor().onRefresh();
	// Publish the final event.
	publishEvent(new ContextRefreshedEvent(this));
	// Participate in LiveBeansView MBean, if active.
	LiveBeansView.registerApplicationContext(this);
}

public void onRefresh() {
	startBeans(true);
	this.running = true;
}

private void startBeans(boolean autoStartupOnly) {
	// 拿到容器中所有的Lifecycle
	Map<String, Lifecycle> lifecycleBeans = getLifecycleBeans();
	Map<Integer, LifecycleGroup> phases = new HashMap<>();
	lifecycleBeans.forEach((beanName, bean) -> {
		if (!autoStartupOnly || (bean instanceof SmartLifecycle && ((SmartLifecycle) bean).isAutoStartup())) {
			// autoStartupOnly=false，表示调用的Lifecycle
			// autoStartupOnly=true，表示调用的SmartLifecycle
			int phase = getPhase(bean);
			// 根据phase进行分组
			LifecycleGroup group = phases.get(phase);
			if (group == null) {
				group = new LifecycleGroup(phase, this.timeoutPerShutdownPhase, lifecycleBeans, autoStartupOnly);
				phases.put(phase, group);
			}
			group.add(beanName, bean);
		}
	});
	if (!phases.isEmpty()) {
		List<Integer> keys = new ArrayList<>(phases.keySet());
		Collections.sort(keys);
		for (Integer key : keys) {
			// 调用start()
			phases.get(key).start();
		}
	}
}