/*
* Copyright 2002-2015 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.context;
/**
* 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);
}