Introduce ConfigurableApplicationContext.pause() and SmartLifecycle.isPauseable()

Closes gh-35269

spring-context/src/main/java/org/springframework/context/ConfigurableApplicationContext.java

@@ -221,16 +221,27 @@ public interface ConfigurableApplicationContext extends ApplicationContext, Life
 	void refresh() throws BeansException, IllegalStateException;
 
 	/**
-	 * Stop all beans in this application context if necessary, and subsequently
+	 * Pause all beans in this application context if necessary, and subsequently
 	 * restart all auto-startup beans, effectively restoring the lifecycle state
 	 * after {@link #refresh()} (typically after a preceding {@link #stop()} call
 	 * when a full {@link #start()} of even lazy-starting beans is to be avoided).
 	 * @since 7.0
-	 * @see #stop()
+	 * @see #pause()
+	 * @see #start()
 	 * @see SmartLifecycle#isAutoStartup()
 	 */
 	void restart();
 
+	/**
+	 * Stop all beans in this application context unless they explicitly opt out of
+	 * pausing through {@link SmartLifecycle#isPauseable()} returning {@code false}.
+	 * @since 7.0
+	 * @see #restart()
+	 * @see #stop()
+	 * @see SmartLifecycle#isPauseable()
+	 */
+	void pause();
+
 	/**
 	 * Register a shutdown hook with the JVM runtime, closing this context
 	 * on JVM shutdown unless it has already been closed at that time.

spring-context/src/main/java/org/springframework/context/LifecycleProcessor.java

@@ -44,6 +44,15 @@ public interface LifecycleProcessor extends Lifecycle {
 		start();
 	}
 
+	/**
+	 * Notification of context pause for auto-stopping components.
+	 * @since 7.0
+	 * @see ConfigurableApplicationContext#pause()
+	 */
+	default void onPause() {
+		stop();
+	}
+
 	/**
 	 * Notification of context close phase for auto-stopping components
 	 * before destruction.

spring-context/src/main/java/org/springframework/context/SmartLifecycle.java

@@ -85,7 +85,7 @@ 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.
+	 * {@link ApplicationContext} gets refreshed or restarted.
 	 * <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.
@@ -93,12 +93,35 @@ public interface SmartLifecycle extends Lifecycle, Phased {
 	 * @see #start()
 	 * @see #getPhase()
 	 * @see LifecycleProcessor#onRefresh()
+	 * @see LifecycleProcessor#onRestart()
 	 * @see ConfigurableApplicationContext#refresh()
+	 * @see ConfigurableApplicationContext#restart()
 	 */
 	default boolean isAutoStartup() {
 		return true;
 	}
 
+	/**
+	 * Returns {@code true} if this {@code Lifecycle} component is able to
+	 * participate in a restart sequence, receiving corresponding {@link #stop()}
+	 * and {@link #start()} calls with a potential pause in-between.
+	 * <p>A value of {@code false} indicates that the component prefers to
+	 * be skipped in a pause scenario, neither receiving a {@link #stop()}
+	 * call nor a subsequent {@link #start()} call, analogous to a plain
+	 * {@link Lifecycle} implementation. It will only receive a {@link #stop()}
+	 * call on close and on explicit context-wide stopping but not on pause.
+	 * <p>The default implementation returns {@code true}.
+	 * @since 7.0
+	 * @see #stop()
+	 * @see LifecycleProcessor#onPause()
+	 * @see LifecycleProcessor#onClose()
+	 * @see ConfigurableApplicationContext#pause()
+	 * @see ConfigurableApplicationContext#close()
+	 */
+	default boolean isPauseable() {
+		return true;
+	}
+
 	/**
 	 * Indicates that a Lifecycle component must stop if it is currently running.
 	 * <p>The provided callback is used by the {@link LifecycleProcessor} to support

spring-context/src/main/java/org/springframework/context/event/ContextPausedEvent.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2002-present 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.event;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * Event raised when an {@code ApplicationContext} gets paused.
+ *
+ * <p>Note that {@code ContextPausedEvent} is a specialization of
+ * {@link ContextStoppedEvent}.
+ *
+ * @author Juergen Hoeller
+ * @since 7.0
+ * @see ConfigurableApplicationContext#pause()
+ * @see ContextRestartedEvent
+ * @see ContextStoppedEvent
+ */
+@SuppressWarnings("serial")
+public class ContextPausedEvent extends ContextStoppedEvent {
+
+	/**
+	 * Create a new {@code ContextRestartedEvent}.
+	 * @param source the {@code ContextPausedEvent} that has been restarted
+	 * (must not be {@code null})
+	 */
+	public ContextPausedEvent(ApplicationContext source) {
+		super(source);
+	}
+
+}

spring-context/src/main/java/org/springframework/context/event/ContextRestartedEvent.java

@@ -17,6 +17,7 @@
 package org.springframework.context.event;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 
 /**
  * Event raised when an {@code ApplicationContext} gets restarted.
@@ -26,8 +27,9 @@ import org.springframework.context.ApplicationContext;
  *
  * @author Sam Brannen
  * @since 7.0
+ * @see ConfigurableApplicationContext#restart()
+ * @see ContextPausedEvent
  * @see ContextStartedEvent
- * @see ContextStoppedEvent
  */
 @SuppressWarnings("serial")
 public class ContextRestartedEvent extends ContextStartedEvent {

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -66,6 +66,7 @@ import org.springframework.context.PayloadApplicationEvent;
 import org.springframework.context.ResourceLoaderAware;
 import org.springframework.context.event.ApplicationEventMulticaster;
 import org.springframework.context.event.ContextClosedEvent;
+import org.springframework.context.event.ContextPausedEvent;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.event.ContextRestartedEvent;
 import org.springframework.context.event.ContextStartedEvent;
@@ -1555,6 +1556,12 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 		publishEvent(new ContextRestartedEvent(this));
 	}
 
+	@Override
+	public void pause() {
+		getLifecycleProcessor().onPause();
+		publishEvent(new ContextPausedEvent(this));
+	}
+
 	@Override
 	public boolean isRunning() {
 		return (this.lifecycleProcessor != null && this.lifecycleProcessor.isRunning());

spring-context/src/main/java/org/springframework/context/support/DefaultLifecycleProcessor.java

@@ -287,7 +287,7 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 	 */
 	@Override
 	public void stop() {
-		stopBeans();
+		stopBeans(false);
 		this.running = false;
 	}
 
@@ -308,7 +308,7 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 		catch (ApplicationContextException ex) {
 			// Some bean failed to auto-start within context refresh:
 			// stop already started beans on context refresh failure.
-			stopBeans();
+			stopBeans(false);
 			throw ex;
 		}
 		this.running = true;
@@ -318,15 +318,23 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 	public void onRestart() {
 		this.stoppedBeans = null;
 		if (this.running) {
-			stopBeans();
+			stopBeans(true);
 		}
 		startBeans(true);
 		this.running = true;
 	}
 
+	@Override
+	public void onPause() {
+		if (this.running) {
+			stopBeans(true);
+			this.running = false;
+		}
+	}
+
 	@Override
 	public void onClose() {
-		stopBeans();
+		stopBeans(false);
 		this.running = false;
 	}
 
@@ -341,7 +349,7 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 	void stopForRestart() {
 		if (this.running) {
 			this.stoppedBeans = ConcurrentHashMap.newKeySet();
-			stopBeans();
+			stopBeans(false);
 			this.running = false;
 		}
 	}
@@ -361,7 +369,8 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 		lifecycleBeans.forEach((beanName, bean) -> {
 			if (!autoStartupOnly || isAutoStartupCandidate(beanName, bean)) {
 				int startupPhase = getPhase(bean);
-				phases.computeIfAbsent(startupPhase, phase -> new LifecycleGroup(phase, lifecycleBeans, autoStartupOnly))
+				phases.computeIfAbsent(
+						startupPhase, phase -> new LifecycleGroup(phase, lifecycleBeans, autoStartupOnly, false))
 						.add(beanName, bean);
 			}
 		});
@@ -424,13 +433,14 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 				(!(bean instanceof SmartLifecycle smartLifecycle) || smartLifecycle.isAutoStartup()));
 	}
 
-	private void stopBeans() {
+	private void stopBeans(boolean pauseableOnly) {
 		Map<String, Lifecycle> lifecycleBeans = getLifecycleBeans();
 		Map<Integer, LifecycleGroup> phases = new TreeMap<>(Comparator.reverseOrder());
 
 		lifecycleBeans.forEach((beanName, bean) -> {
 			int shutdownPhase = getPhase(bean);
-			phases.computeIfAbsent(shutdownPhase, phase -> new LifecycleGroup(phase, lifecycleBeans, false))
+			phases.computeIfAbsent(
+					shutdownPhase, phase -> new LifecycleGroup(phase, lifecycleBeans, false, pauseableOnly))
 					.add(beanName, bean);
 		});
 
@@ -446,13 +456,13 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 	 * @param beanName the name of the bean to stop
 	 */
 	private void doStop(Map<String, ? extends Lifecycle> lifecycleBeans, final String beanName,
-			final CountDownLatch latch, final Set<String> countDownBeanNames) {
+			boolean pauseableOnly, final CountDownLatch latch, final Set<String> countDownBeanNames) {
 
 		Lifecycle bean = lifecycleBeans.remove(beanName);
 		if (bean != null) {
 			String[] dependentBeans = getBeanFactory().getDependentBeans(beanName);
 			for (String dependentBean : dependentBeans) {
-				doStop(lifecycleBeans, dependentBean, latch, countDownBeanNames);
+				doStop(lifecycleBeans, dependentBean, pauseableOnly, latch, countDownBeanNames);
 			}
 			try {
 				if (bean.isRunning()) {
@@ -461,20 +471,22 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 						stoppedBeans.add(beanName);
 					}
 					if (bean instanceof SmartLifecycle smartLifecycle) {
-						if (logger.isTraceEnabled()) {
-							logger.trace("Asking bean '" + beanName + "' of type [" +
-									bean.getClass().getName() + "] to stop");
-						}
-						countDownBeanNames.add(beanName);
-						smartLifecycle.stop(() -> {
-							latch.countDown();
-							countDownBeanNames.remove(beanName);
-							if (logger.isDebugEnabled()) {
-								logger.debug("Bean '" + beanName + "' completed its stop procedure");
+						if (!pauseableOnly || smartLifecycle.isPauseable()) {
+							if (logger.isTraceEnabled()) {
+								logger.trace("Asking bean '" + beanName + "' of type [" +
+										bean.getClass().getName() + "] to stop");
 							}
-						});
+							countDownBeanNames.add(beanName);
+							smartLifecycle.stop(() -> {
+								latch.countDown();
+								countDownBeanNames.remove(beanName);
+								if (logger.isDebugEnabled()) {
+									logger.debug("Bean '" + beanName + "' completed its stop procedure");
+								}
+							});
+						}
 					}
-					else {
+					else if (!pauseableOnly) {
 						if (logger.isTraceEnabled()) {
 							logger.trace("Stopping bean '" + beanName + "' of type [" +
 									bean.getClass().getName() + "]");
@@ -562,14 +574,19 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 
 		private final boolean autoStartupOnly;
 
+		private final boolean pauseableOnly;
+
 		private final List<LifecycleGroupMember> members = new ArrayList<>();
 
 		private int smartMemberCount;
 
-		public LifecycleGroup(int phase, Map<String, ? extends Lifecycle> lifecycleBeans, boolean autoStartupOnly) {
+		public LifecycleGroup(int phase, Map<String, ? extends Lifecycle> lifecycleBeans,
+				boolean autoStartupOnly, boolean pauseableOnly) {
+
 			this.phase = phase;
 			this.lifecycleBeans = lifecycleBeans;
 			this.autoStartupOnly = autoStartupOnly;
+			this.pauseableOnly = pauseableOnly;
 		}
 
 		public void add(String name, Lifecycle bean) {
@@ -621,7 +638,7 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 			Set<String> lifecycleBeanNames = new HashSet<>(this.lifecycleBeans.keySet());
 			for (LifecycleGroupMember member : this.members) {
 				if (lifecycleBeanNames.contains(member.name)) {
-					doStop(this.lifecycleBeans, member.name, latch, countDownBeanNames);
+					doStop(this.lifecycleBeans, member.name, this.pauseableOnly, latch, countDownBeanNames);
 				}
 				else if (member.bean instanceof SmartLifecycle) {
 					// Already removed: must have been a dependent bean from another phase