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/*
 * Copyright 2002-2019 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
 *
 *      https://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 {@code 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 {@code run()} method upon shutdown completion to avoid unnecessary * delays in the overall {@code ApplicationContext} shutdown. * *

This interface extends {@link Phased}, and the {@link #getPhase()} method's * return value indicates the phase within which this {@code Lifecycle} component * should be started and stopped. The startup process begins with the lowest * phase value and ends with the highest phase value ({@code Integer.MIN_VALUE} * is the lowest possible, and {@code 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 {@code Lifecycle} components within the context that do not also * implement {@code SmartLifecycle} will be treated as if they have a phase * value of {@code 0}. This allows a {@code SmartLifecycle} component to start * before those {@code Lifecycle} components if the {@code SmartLifecycle} * component has a negative phase value, or the {@code SmartLifecycle} component * may start after those {@code Lifecycle} components if the {@code SmartLifecycle} * component has a positive phase value. * *

Note that, due to the auto-startup support in {@code SmartLifecycle}, a * {@code 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 {@code SmartLifecycle} beans. * * @author Mark Fisher * @author Juergen Hoeller * @author Sam Brannen * @since 3.0 * @see LifecycleProcessor * @see ConfigurableApplicationContext */ public interface SmartLifecycle extends Lifecycle, Phased { /** * The default phase for {@code SmartLifecycle}: {@code Integer.MAX_VALUE}. *

This is different from the common phase {@code 0} associated with regular * {@link Lifecycle} implementations, putting the typically auto-started * {@code SmartLifecycle} beans into a later startup phase and an earlier * shutdown phase. * @since 5.1 * @see #getPhase() * @see org.springframework.context.support.DefaultLifecycleProcessor#getPhase(Lifecycle) */ int DEFAULT_PHASE = Integer.MAX_VALUE; /** * 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. *

The default implementation returns {@code true}. * @see #start() * @see #getPhase() * @see LifecycleProcessor#onRefresh() * @see ConfigurableApplicationContext#refresh() */ default boolean isAutoStartup() { return true; } /** * 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. *

The default implementation delegates to {@link #stop()} and immediately * triggers the given callback in the calling thread. Note that there is no * synchronization between the two, so custom implementations may at least * want to put the same steps within their common lifecycle monitor (if any). * @see #stop() * @see #getPhase() */ default void stop(Runnable callback) { stop(); callback.run(); } /** * Return the phase that this lifecycle object is supposed to run in. *

The default implementation returns {@link #DEFAULT_PHASE} in order to * let {@code stop()} callbacks execute after regular {@code Lifecycle} * implementations. * @see #isAutoStartup() * @see #start() * @see #stop(Runnable) * @see org.springframework.context.support.DefaultLifecycleProcessor#getPhase(Lifecycle) */ @Override default int getPhase() { return DEFAULT_PHASE; } }





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