Introduce ConfigurableApplicationContext.restart() method

Closes gh-35171

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

@@ -220,6 +220,17 @@ public interface ConfigurableApplicationContext extends ApplicationContext, Life
 	 */
 	void refresh() throws BeansException, IllegalStateException;
 
+	/**
+	 * Stop 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 SmartLifecycle#isAutoStartup()
+	 */
+	void restart();
+
 	/**
 	 * 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

@@ -26,13 +26,31 @@ package org.springframework.context;
 public interface LifecycleProcessor extends Lifecycle {
 
 	/**
-	 * Notification of context refresh, for example, for auto-starting components.
+	 * Notification of context refresh for auto-starting components.
+	 * @see ConfigurableApplicationContext#refresh()
 	 */
-	void onRefresh();
+	default void onRefresh() {
+		start();
+	}
 
 	/**
-	 * Notification of context close phase, for example, for auto-stopping components.
+	 * Notification of context restart for auto-stopping and subsequently
+	 * auto-starting components.
+	 * @since 7.0
+	 * @see ConfigurableApplicationContext#restart()
 	 */
-	void onClose();
+	default void onRestart() {
+		stop();
+		start();
+	}
+
+	/**
+	 * Notification of context close phase for auto-stopping components
+	 * before destruction.
+	 * @see ConfigurableApplicationContext#close()
+	 */
+	default void onClose() {
+		stop();
+	}
 
 }

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

@@ -1548,6 +1548,12 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 		publishEvent(new ContextStoppedEvent(this));
 	}
 
+	@Override
+	public void restart() {
+		getLifecycleProcessor().onRestart();
+		publishEvent(new ContextStartedEvent(this));
+	}
+
 	@Override
 	public boolean isRunning() {
 		return (this.lifecycleProcessor != null && this.lifecycleProcessor.isRunning());

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

@@ -314,6 +314,16 @@ public class DefaultLifecycleProcessor implements LifecycleProcessor, BeanFactor
 		this.running = true;
 	}
 
+	@Override
+	public void onRestart() {
+		this.stoppedBeans = null;
+		if (this.running) {
+			stopBeans();
+		}
+		startBeans(true);
+		this.running = true;
+	}
+
 	@Override
 	public void onClose() {
 		stopBeans();

spring-context/src/test/java/org/springframework/context/support/DefaultLifecycleProcessorTests.java

@@ -348,6 +348,40 @@ class DefaultLifecycleProcessorTests {
 		context.close();
 	}
 
+	@Test
+	void contextRefreshThenRestartWithMixedBeans() {
+		StaticApplicationContext context = new StaticApplicationContext();
+		CopyOnWriteArrayList<Lifecycle> stoppedBeans = new CopyOnWriteArrayList<>();
+		TestSmartLifecycleBean smartBean1 = TestSmartLifecycleBean.forShutdownTests(5, 0, stoppedBeans);
+		TestSmartLifecycleBean smartBean2 = TestSmartLifecycleBean.forShutdownTests(-3, 0, stoppedBeans);
+		smartBean2.setAutoStartup(false);
+		context.getBeanFactory().registerSingleton("smartBean1", smartBean1);
+		context.getBeanFactory().registerSingleton("smartBean2", smartBean2);
+
+		assertThat(smartBean1.isRunning()).isFalse();
+		assertThat(smartBean2.isRunning()).isFalse();
+		context.refresh();
+		assertThat(smartBean1.isRunning()).isTrue();
+		assertThat(smartBean2.isRunning()).isFalse();
+		context.restart();
+		assertThat(stoppedBeans).containsExactly(smartBean1);
+		assertThat(smartBean1.isRunning()).isTrue();
+		assertThat(smartBean2.isRunning()).isFalse();
+		smartBean1.stop();
+		assertThat(stoppedBeans).containsExactly(smartBean1, smartBean1);
+		assertThat(smartBean1.isRunning()).isFalse();
+		assertThat(smartBean2.isRunning()).isFalse();
+		context.restart();
+		assertThat(stoppedBeans).containsExactly(smartBean1, smartBean1);
+		assertThat(smartBean1.isRunning()).isTrue();
+		assertThat(smartBean2.isRunning()).isFalse();
+		context.start();
+		assertThat(smartBean1.isRunning()).isTrue();
+		assertThat(smartBean2.isRunning()).isTrue();
+		context.close();
+		assertThat(stoppedBeans).containsExactly(smartBean1, smartBean1, smartBean1, smartBean2);
+	}
+
 	@Test
 	@EnabledForTestGroups(LONG_RUNNING)
 	void smartLifecycleGroupShutdown() {
@@ -741,17 +775,22 @@ class DefaultLifecycleProcessorTests {
 			// invocation order in the 'stoppedBeans' list
 			stop();
 			final int delay = this.shutdownDelay;
-			new Thread(() -> {
-				try {
-					Thread.sleep(delay);
-				}
-				catch (InterruptedException e) {
-					// ignore
-				}
-				finally {
-					callback.run();
-				}
-			}).start();
+			if (delay > 0) {
+				new Thread(() -> {
+					try {
+						Thread.sleep(delay);
+					}
+					catch (InterruptedException e) {
+						// ignore
+					}
+					finally {
+						callback.run();
+					}
+				}).start();
+			}
+			else {
+				callback.run();
+			}
 		}
 	}