Spring中SmartLifecycle的用法解读 Spring中SmartLifecycle的用法解读

Spring SmartLifecycle用法

SmartLifecycle 是一个接口

SmartLifecycle 解读

1、接口定义
2、应用

Spring SmartLifecycle用法 Spring SmartLifecycle 在容器所有bean加载和初始化完毕执行
在使用Spring开发时，我们都知道，所有bean都交给Spring容器来统一管理，其中包括每一个bean的加载和初始化。
有时候我们需要在Spring加载和初始化所有bean后，接着执行一些任务或者启动需要的异步服务，这样我们可以使用 SmartLifecycle 来做到。

SmartLifecycle 是一个接口
当Spring容器加载所有bean并完成初始化之后，会接着回调实现该接口的类中对应的方法（start()方法）。

import org.springframework.context.SmartLifecycle; import org.springframework.stereotype.Component; /** * SmartLifecycle测试 * * * */@Componentpublic class TestSmartLifecycle implements SmartLifecycle {private boolean isRunning = false; /*** 1. 我们主要在该方法中启动任务或者其他异步服务，比如开启MQ接收消息
* 2. 当上下文被刷新（所有对象已被实例化和初始化之后）时，将调用该方法，默认生命周期处理器将检查每个SmartLifecycle对象的isAutoStartup()方法返回的布尔值。* 如果为“true”，则该方法会被调用，而不是等待显式调用自己的start()方法。*/@Overridepublic void start() {System.out.println("start"); // 执行完其他业务后，可以修改 isRunning = trueisRunning = true; }/*** 如果工程中有多个实现接口SmartLifecycle的类，则这些类的start的执行顺序按getPhase方法返回值从小到大执行。
* 例如：1比2先执行，-1比0先执行。 stop方法的执行顺序则相反，getPhase返回值较大类的stop方法先被调用，小的后被调用。*/@Overridepublic int getPhase() {// 默认为0return 0; }/*** 根据该方法的返回值决定是否执行start方法。
* 返回true时start方法会被自动执行，返回false则不会。*/@Overridepublic boolean isAutoStartup() {// 默认为falsereturn true; }/*** 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。*/@Overridepublic boolean isRunning() {// 默认返回falsereturn isRunning; }/*** SmartLifecycle子类的才有的方法，当isRunning方法返回true时，该方法才会被调用。*/@Overridepublic void stop(Runnable callback) {System.out.println("stop(Runnable)"); // 如果你让isRunning返回true，需要执行stop这个方法，那么就不要忘记调用callback.run()。// 否则在你程序退出时，Spring的DefaultLifecycleProcessor会认为你这个TestSmartLifecycle没有stop完成，程序会一直卡着结束不了，等待一定时间（默认超时时间30秒）后才会自动结束。// PS：如果你想修改这个默认超时时间，可以按下面思路做，当然下面代码是springmvc配置文件形式的参考，在SpringBoot中自然不是配置xml来完成，这里只是提供一种思路。// ////// callback.run(); isRunning = false; }/*** 接口Lifecycle的子类的方法，只有非SmartLifecycle的子类才会执行该方法。
* 1. 该方法只对直接实现接口Lifecycle的类才起作用，对实现SmartLifecycle接口的类无效。
* 2. 方法stop()和方法stop(Runnable callback)的区别只在于，后者是SmartLifecycle子类的专属。*/@Overridepublic void stop() {System.out.println("stop"); isRunning = false; }}

SmartLifecycle 解读 org.springframework.context.SmartLifecycle解读

1、接口定义

/** * An extension of the {@link Lifecycle} interface for those objects that require to * be started upon ApplicationContext refresh and/or shutdown in a particular order. * The {@link #isAutoStartup()} return value indicates whether this object should * be started at the time of a context refresh. The callback-accepting * {@link #stop(Runnable)} method is useful for objects that have an asynchronous * shutdown process. Any implementation of this interface must invoke the * callback's run() method upon shutdown completion to avoid unnecessary delays * in the overall ApplicationContext shutdown. * * This interface extends {@link Phased}, and the {@link #getPhase()} method's * return value indicates the phase within which this Lifecycle component should * be started and stopped. The startup process begins with the lowest * phase value and ends with the highest phase value (Integer.MIN_VALUE * is the lowest possible, and Integer.MAX_VALUE is the highest possible). The * shutdown process will apply the reverse order. Any components with the * same value will be arbitrarily ordered within the same phase. * * Example: if component B depends on component A having already started, then * component A should have a lower phase value than component B. During the * shutdown process, component B would be stopped before component A. * * Any explicit "depends-on" relationship will take precedence over * the phase order such that the dependent bean always starts after its * dependency and always stops before its dependency. * * Any Lifecycle components within the context that do not also implement * SmartLifecycle will be treated as if they have a phase value of 0. That * way a SmartLifecycle implementation may start before those Lifecycle * components if it has a negative phase value, or it may start after * those components if it has a positive phase value. * * Note that, due to the auto-startup support in SmartLifecycle, * a SmartLifecycle bean instance will get initialized on startup of the * application context in any case. As a consequence, the bean definition * lazy-init flag has very limited actual effect on SmartLifecycle beans. * * @author Mark Fisher * @since 3.0 * @see LifecycleProcessor * @see ConfigurableApplicationContext */public interface SmartLifecycle extends Lifecycle, Phased { /*** Returns {@code true} if this {@code Lifecycle} component should get* started automatically by the container at the time that the containing* {@link ApplicationContext} gets refreshed.* A value of {@code false} indicates that the component is intended to* be started through an explicit {@link #start()} call instead, analogous* to a plain {@link Lifecycle} implementation.* @see #start()* @see #getPhase()* @see LifecycleProcessor#onRefresh()* @see ConfigurableApplicationContext#refresh()*/ boolean isAutoStartup(); /*** Indicates that a Lifecycle component must stop if it is currently running.* The provided callback is used by the {@link LifecycleProcessor} to support* an ordered, and potentially concurrent, shutdown of all components having a* common shutdown order value. The callback must be executed after* the {@code SmartLifecycle} component does indeed stop.* The {@link LifecycleProcessor} will call only this variant of the* {@code stop} method; i.e. {@link Lifecycle#stop()} will not be called for* {@code SmartLifecycle} implementations unless explicitly delegated to within* the implementation of this method.* @see #stop()* @see #getPhase()*/ void stop(Runnable callback); }

从注释文档里可以看出：
1、是接口 Lifecycle 的拓展，且会在应用上下文类ApplicationContext 执行 refresh and/or shutdown 时会调用
2、方法 isAutoStartup() 返回的值会决定，当前实体对象是否会被调用，当应用上下文类ApplicationContext 执行 refresh
3、stop(Runnable) 方法用于调用Lifecycle的stop方法
4、getPhase() 返回值用于设置LifeCycle的执行优先度：值越小优先度越高
5、isRunning() 决定了start()方法的是否调用

2、应用

public class SmartLifecycleImpl implements SmartLifecycle {private Boolean isRunning = false; @Overridepublic boolean isAutoStartup() {return true; } @Overridepublic void stop(Runnable callback) {callback.run(); } @Overridepublic void start() {System.out.println("SmartLifecycleImpl is starting ...."); isRunning = true; } @Overridepublic void stop() {System.out.println("SmartLifecycleImpl is stopped."); }/*** 执行start()方法前会用它来判断是否执行，返回为true时，start()方法不执行*/@Overridepublic boolean isRunning() {return isRunning; } @Overridepublic int getPhase() {return 0; }}

启动类

public class ProviderBootstrap { public static void main(String[] args) throws Exception {AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ProviderConfiguration.class); context.start(); System.in.read(); } @Configurationstatic class ProviderConfiguration { @Beanpublic SmartLifecycleImpl getSmartLifecycleImpl(){return new SmartLifecycleImpl(); }}}

可以发现，类SmartLifecycleImpl提交给spring容器后，启动后，会输出 start() 方法的方法体。
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