简介
Bean的初始化方法和销毁方法是Bean生命周期级别的;而Lifecycle是容器生命周期级别的。如果我们想在容器本身的生命周期(比如容器启动完成后、停止之前)事件上做一些工作,可以使用LifeCycle接口。
LifeCycle
简介
源码
public interface Lifecycle {
void start();
void stop();
boolean isRunning();
}
start:如果类A没在运行(isRunning返回false),则走该方法;否则不走该方法
stop:如果类A在运行(isRunning返回true),则走该方法;否则不走该方法
isRunning:返回true表示类A已经运行,返回false表示类A没运行
简单示例
isRunning返回true
代码
package com.example.config;
import org.springframework.context.Lifecycle;
import org.springframework.stereotype.Component;
public class MyLifeCycle implements Lifecycle {
public void start() {
System.out.println("start");
}
public void stop() {
System.out.println("stop");
}
public boolean isRunning() {
System.out.println("isRunning");
return true;
}
}
结果
启动时无打印
关闭时:
isRunning
stop
isRunning返回false
package com.example.config;
import org.springframework.context.Lifecycle;
import org.springframework.stereotype.Component;
public class MyLifeCycle implements Lifecycle {
public void start() {
System.out.println("start");
}
public void stop() {
System.out.println("stop");
}
public boolean isRunning() {
System.out.println("isRunning");
return false;
}
}
结果
启动时无打印
关闭时
isRunning
改动isRunning值
我本以为,手动改isRunning返回值即可让它既执行start()又执行stop(),但我错了,如下所示:
package com.example.config;
import org.springframework.context.Lifecycle;
import org.springframework.stereotype.Component;
public class MyLifeCycle implements Lifecycle {
private volatile boolean running = false;
public void start() {
System.out.println("start");
running = true;
}
public void stop() {
System.out.println("stop");
}
public boolean isRunning() {
System.out.println("isRunning");
return running;
}
}
结果
启动时无打印
关闭时:
isRunning
显式调用start()
在上边“简单示例” 可以发现,无论怎么搞,都调用不到start()方法!!。有人说必须显式去调用它,如下所示:
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(
"com.example.config.MyLifecycle");
ctx.start();
ctx.close();
}
但是,我只看到如下输出:
19:20:23.914 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@3ab39c39
19:20:23.924 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalConfigurationAnnotationProcessor'
19:20:23.944 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerProcessor'
19:20:23.944 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.event.internalEventListenerFactory'
19:20:23.944 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalAutowiredAnnotationProcessor'
19:20:23.944 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.annotation.internalCommonAnnotationProcessor'
19:20:23.964 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'spring.liveBeansView.mbeanDomain' in PropertySource 'systemProperties' with value of type String
19:20:23.974 [main] DEBUG org.springframework.context.annotation.AnnotationConfigApplicationContext - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@3ab39c39, started on Tue Mar 09 19:20:23 CST 2021
19:20:23.974 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'spring.liveBeansView.mbeanDomain' in PropertySource 'systemProperties' with value of type String
对此,该有一张黑人问号脸。。。留到以后再看为什么会这样吧
SmartLifeCycle
简介
说明
SmartLifecycle是Lifecycle的一个子接口,比Lifecycle有更丰富的功能。其中有两点最重要的改进:
- 无需容器显示调用start()方法,就可以回调SmartLifecycle接口的start()
- 容器中如果有多个SmartLifecycle实例,可以方便控制调用顺序。
方法
方法名 | 描述 |
isAutoStartup() | 一定要返回true。否则,容器启动时不会回调start()方法。 true:让Lifecycle类所在的上下文在调用`refresh`时,能够自己自动进行回调。 |
getPhase() | 控制多个SmartLifecycle的回调顺序的:越小:start()方法越靠前,stop()方法越靠后 |
isRunning() | 与Lifecycle接口中的功能一样,用来判你的断组件是否在运行。 |
start() | 如果类A没在运行(isRunning返回false),则走该方法;否则不走该方法。 当刷新容器(启动完成)时调用。跟Lifecycle接口一样。 |
stop(Runnable callback) | 当容器停止时,回调该方法。 当执行完你自定义的逻辑后,一定要调用下callback.run(); 这是为了,告诉容器你已停止自己的组件完成。 此方法是有超时时间的,默认为30s。可以通过以下方式设置超时时间 |
stop() | 需要自己调用。不会被Spring框架调用到 |
stop(Runnable callback)
其他网址:Spring 5.0.0框架介绍_中文版_3.6
在SmartLifecycle中定义的停止方法接收一个回调函数。任何实现在关闭进程完成之后都必须调用回调的run()方法。当需要时这可以进行异步关闭,因为LifecycleProcessor接口、DefaultLifecycleProcessor接口的默认实现会等待每个阶段的对象组直到达到超时值,然后调用回调函数。默认每个阶段的超时值为30秒。可以在上下文中通过定义名为”lifecycleProcessor”的bean来覆盖默认的生命周期处理器实例。如果你只想修改超时值,这样改即可:
<bean id="lifecycleProcessor" class="org.springframework.context.support.DefaultLifecycleProcessor">
<!-- timeout value in milliseconds -->
<property name="timeoutPerShutdownPhase" value="10000"/>
</bean>
简单示例
代码
package com.example.config;
import org.springframework.context.SmartLifecycle;
import org.springframework.stereotype.Component;
public class MySmartLifecycle implements SmartLifecycle {
private volatile boolean running = false;
/**
* true:让Lifecycle类所在的上下文在调用`refresh`时,能够自己自动进行回调
* false: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。
*/
public boolean isAutoStartup() {
return true;
}
/**
* 很多框架中,把真正逻辑写在stop()方法内。比如quartz和Redis的spring支持包
*/
public void stop(Runnable callback) {
System.out.println("stop(callback)");
stop();
callback.run();
}
public void start() {
System.out.println("start()");
running = true;
}
public void stop() {
System.out.println("stop()");
running = false;
}
public boolean isRunning() {
System.out.println("isRunning()");
return running;
}
/**
* 阶段值。越小:start()方法越靠前,stop()方法越靠后
*/
public int getPhase() {
System.out.println("getPhase()");
return 0;
}
}
测试
启动时:
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.3.0.RELEASE)
2021-03-09 19:30:57.138 INFO 6600 --- [ main] com.example.DemoApplication : Starting DemoApplication on DESKTOP-QI6B9ME with PID 6600 (E:\work\Idea_proj\demo_JAVA\demo_SpringBoot\target\classes started by Liu in E:\work\Idea_proj\demo_JAVA\demo_SpringBoot)
2021-03-09 19:30:57.143 INFO 6600 --- [ main] com.example.DemoApplication : No active profile set, falling back to default profiles: default
2021-03-09 19:30:57.899 INFO 6600 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2021-03-09 19:30:57.907 INFO 6600 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2021-03-09 19:30:57.907 INFO 6600 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.35]
2021-03-09 19:30:57.986 INFO 6600 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2021-03-09 19:30:57.986 INFO 6600 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 808 ms
2021-03-09 19:30:58.135 INFO 6600 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
getPhase()
isRunning()
start()
2021-03-09 19:30:58.260 INFO 6600 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2021-03-09 19:30:58.268 INFO 6600 --- [ main] com.example.DemoApplication : Started DemoApplication in 1.442 seconds (JVM running for 2.44)
关闭时:
getPhase()
isRunning()
stop(callback)
stop()