為什么在春季啟動和停止bean的概念

Question

可以完成bean初始化/清除的不同方法。 也有其他事件機制。 伴隨着所有這些，spring為什么具有啟動上下文的概念，我相信它會調用bean的相應start和stop方法。

為了進行測試，我有一段看起來像這樣的代碼-

public class Car implements InitializingBean, DisposableBean, SmartLifecycle {

     private Engine engine;

     private volatile boolean isRunning = false;


    @Override
    public void afterPropertiesSet() throws Exception {
        logger.debug("Car -- afterPropertiesSet");
    }

    @Override
    public void destroy() throws Exception {
        logger.debug("Car -- destroy");
    }

    @PostConstruct
    public void postConstruction() {
        logger.debug("Car -- postConstruct");
    }

    @PreDestroy
    public void preDestruction() {
        logger.debug("Car -- preDestroy");
    }


    @Override
    public void stop() {
        //Note that this stop notification is not guaranteed to come before destruction: On regular shutdown, 
        //Lifecycle beans will first receive a stop notification before the general destruction callbacks are being propagated; 
        //however, on hot refresh during a context's lifetime or on aborted refresh attempts, only destroy methods will be called.
        logger.debug("Car -- stop");
        isRunning = false;
    }

    @Override
    public boolean isRunning() {
        //Check whether this component is currently running.
        //In the case of a container, this will return true only if all components that apply are currently running.
        logger.debug("Car -- isRunning");
        return isRunning;
    }

    @Override
    public int getPhase() {
        //Return the phase value of this object.
        logger.debug("Car -- getPhase");
        return 10;
    }

    @Override
    public boolean isAutoStartup() {
        //Returns true if this Lifecycle component should get started automatically by the container 
        //A value of false indicates that the component is intended to be started through an explicit start() call instead, 
        //analogous to a automatic Lifecycle.
        logger.debug("Car -- isAutoStartup");
        return false;
    }

    @Override
    public void stop(Runnable callback) {
        logger.debug("Car -- stop -  async");
        isRunning = false;
         try {

           //Sleeping for 10 seconds so that all threads 
           //get enough time to do their cleanup  
           TimeUnit.SECONDS.sleep(10);
           logger.debug("Wait over");
           //Shudown complete. Regular shutdown will continue.
           callback.run();
       } catch (final InterruptedException e) {
           //Looks like we got exception while shutting down, 
           //log it or do something with it
       }
    }

    @Override
    public void start() {
        //Start this component.
        //Should not throw an exception if the component is already running.
        logger.debug("Car -- start");
        isRunning = true;
    }
}

首先，我為isAutoStartUp返回true值，然后嘗試返回false。 下圖是兩次運行的日志文件的比較。 而且，無論autostartup是true / false，代碼都可以正常運行。

Answer 1

這是當您的bean與服務相關時使用的。 您可能想知道它們何時成功啟動，並且在常規應用程序關閉時也具有正確的關閉過程/清理/拆除。