Merge pull request #7336 from mbogoevici/GH-7335-1.4.x

* pr/7336:
  Polish multiple root contexts in `Restarter`
  Support multiple root contexts in `Restarter`

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/RestartApplicationListener.java

@@ -45,15 +45,14 @@ public class RestartApplicationListener
 			onApplicationStartingEvent((ApplicationStartingEvent) event);
 		}
 		if (event instanceof ApplicationPreparedEvent) {
-			Restarter.getInstance()
-					.prepare(((ApplicationPreparedEvent) event).getApplicationContext());
+			onApplicationPreparedEvent((ApplicationPreparedEvent) event);
 		}
 		if (event instanceof ApplicationReadyEvent
 				|| event instanceof ApplicationFailedEvent) {
 			Restarter.getInstance().finish();
-			if (event instanceof ApplicationFailedEvent) {
-				Restarter.getInstance().prepare(null);
-			}
+		}
+		if (event instanceof ApplicationFailedEvent) {
+			onApplicationFailedEvent((ApplicationFailedEvent) event);
 		}
 	}
 
@@ -72,6 +71,14 @@ public class RestartApplicationListener
 		}
 	}
 
+	private void onApplicationPreparedEvent(ApplicationPreparedEvent event) {
+		Restarter.getInstance().prepare(event.getApplicationContext());
+	}
+
+	private void onApplicationFailedEvent(ApplicationFailedEvent event) {
+		Restarter.getInstance().remove(event.getApplicationContext());
+	}
+
 	@Override
 	public int getOrder() {
 		return this.order;

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/Restarter.java

@@ -31,6 +31,7 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.BlockingDeque;
 import java.util.concurrent.Callable;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.LinkedBlockingDeque;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.locks.Lock;
@@ -116,7 +117,7 @@ public class Restarter {
 
 	private boolean finished = false;
 
-	private volatile ConfigurableApplicationContext rootContext;
+	private final List<ConfigurableApplicationContext> rootContexts = new CopyOnWriteArrayList<ConfigurableApplicationContext>();
 
 	/**
 	 * Internal constructor to create a new {@link Restarter} instance.
@@ -314,9 +315,9 @@ public class Restarter {
 		this.logger.debug("Stopping application");
 		this.stopLock.lock();
 		try {
-			if (this.rootContext != null) {
-				this.rootContext.close();
-				this.rootContext = null;
+			for (ConfigurableApplicationContext context : this.rootContexts) {
+				context.close();
+				this.rootContexts.remove(context);
 			}
 			cleanupCaches();
 			if (this.forceReferenceCleanup) {
@@ -418,7 +419,13 @@ public class Restarter {
 		if (applicationContext != null && applicationContext.getParent() != null) {
 			return;
 		}
-		this.rootContext = applicationContext;
+		this.rootContexts.add(applicationContext);
+	}
+
+	void remove(ConfigurableApplicationContext applicationContext) {
+		if (applicationContext != null) {
+			this.rootContexts.remove(applicationContext);
+		}
 	}
 
 	private LeakSafeThread getLeakSafeThread() {

spring-boot-devtools/src/test/java/org/springframework/boot/devtools/restart/RestartApplicationListenerTests.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.devtools.restart;
 
+import java.util.List;
+
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -64,8 +66,8 @@ public class RestartApplicationListenerTests {
 		assertThat(ReflectionTestUtils.getField(Restarter.getInstance(), "args"))
 				.isEqualTo(ARGS);
 		assertThat(Restarter.getInstance().isFinished()).isTrue();
-		assertThat(ReflectionTestUtils.getField(Restarter.getInstance(), "rootContext"))
-				.isNotNull();
+		assertThat((List<?>) ReflectionTestUtils.getField(Restarter.getInstance(),
+				"rootContexts")).isNotEmpty();
 	}
 
 	@Test
@@ -74,8 +76,8 @@ public class RestartApplicationListenerTests {
 		assertThat(ReflectionTestUtils.getField(Restarter.getInstance(), "args"))
 				.isEqualTo(ARGS);
 		assertThat(Restarter.getInstance().isFinished()).isTrue();
-		assertThat(ReflectionTestUtils.getField(Restarter.getInstance(), "rootContext"))
-				.isNull();
+		assertThat((List<?>) ReflectionTestUtils.getField(Restarter.getInstance(),
+				"rootContexts")).isEmpty();
 	}
 
 	@Test