接口 SmartLifecycle

public interface SmartLifecycle
extends Lifecycle, Phased

An extension of the Lifecycle interface for those objects that require to be started upon ApplicationContext refresh and/or shutdown in a particular order.

The isAutoStartup() return value indicates whether this object should be started at the time of a context refresh. The callback-accepting 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 Phased, and the 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. This allows a SmartLifecycle component to start before those Lifecycle components if the SmartLifecycle component has a negative phase value, or the SmartLifecycle component may start after those Lifecycle components if the SmartLifecycle component has a positive phase value.

Note that, due to the auto-startup support in SmartLifecycle, a SmartLifecycle bean instance will usually 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.