Spring中SmartLifecycle的用法解读

import org.springframework.context.SmartLifecycle;

import org.springframework.stereotype.Component;

/**

  * SmartLifecycle测试

  *

  *

  *

  */

@Component

public 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<br/>

      * 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。

      */

     @Override

     public void start() {

         System.out.println( "start" );

         // 执行完其他业务后，可以修改 isRunning = true

         isRunning = 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。<br/>

      * 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。

      */

     @Override

     public int getPhase() {

         // 默认为0

         return 0 ;

     }

     /**

      * 根据该方法的返回值决定是否执行start方法。<br/>

      * 返回true时start方法会被自动执行，返回false则不会。

      */

     @Override

     public boolean isAutoStartup() {

         // 默认为false

         return true ;

     }

     /**

      * 1. 只有该方法返回false时，start方法才会被执行。<br/>

      * 2. 只有该方法返回true时，stop(Runnable callback)或stop()方法才会被执行。

      */

     @Override

     public boolean isRunning() {

         // 默认返回false

         return 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。

      */

     @Override

     public 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。

         // <bean id="lifecycleProcessor" class="org.springframework.context.support.DefaultLifecycleProcessor">

         //      <!-- timeout value in milliseconds -->

         //      <property name="timeoutPerShutdownPhase" value="10000"/>

         // </bean>

         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。<br/>

      * 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。<br/>

      * 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。

      */

     @Override

     public void stop() {

         System.out.println( "stop" );

         isRunning = false ;

     }

}

/**

  * 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 <i>must</i> invoke the

  * callback's run() method upon shutdown completion to avoid unnecessary delays

  * in the overall ApplicationContext shutdown.

  *

  * <p>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 <i>lowest</i>

  * phase value and ends with the <i>highest</i> 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.

  *

  * <p>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.

  *

  * <p>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.

  *

  * <p>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.

  *

  * <p>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.

      * <p>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.

      * <p>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 <b>must</b> be executed after

      * the {@code SmartLifecycle} component does indeed stop.

      * <p>The {@link LifecycleProcessor} will call <i>only</i> 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);

}

public class SmartLifecycleImpl implements SmartLifecycle {

     private Boolean isRunning = false ;

     @Override

     public boolean isAutoStartup() {

         return true ;

     }

     @Override

     public void stop(Runnable callback) {

         callback.run();

     }

     @Override

     public void start() {

         System.out.println( "SmartLifecycleImpl is starting ...." );

         isRunning = true ;

     }

     @Override

     public 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

      */

     @Override

     public boolean isRunning() {

         return isRunning;

     }

     @Override

     public int getPhase() {

         return 0 ;

     }

}

public class ProviderBootstrap {

     public static void main(String[] args) throws Exception {

         AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ProviderConfiguration. class );

         context.start();

         System.in.read();

     }

     @Configuration

     static class ProviderConfiguration {

         @Bean

         public SmartLifecycleImpl getSmartLifecycleImpl(){

             return new SmartLifecycleImpl();

         }

     }

}