Ensure startup failures are only logged once

Update SpringApplication so that startup exceptions are only logged
once. A custom UncaughtExceptionHandler is now used when running in
the main thread to suppress errors that have already been logged.

Fixes gh-4423

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/FileWatchingFailureHandler.java

@@ -42,7 +42,6 @@ class FileWatchingFailureHandler implements FailureHandler {
 
 	@Override
 	public Outcome handle(Throwable failure) {
-		failure.printStackTrace();
 		CountDownLatch latch = new CountDownLatch(1);
 		FileSystemWatcher watcher = this.fileSystemWatcherFactory.getFileSystemWatcher();
 		watcher.addSourceFolders(

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

@@ -50,6 +50,7 @@ class RestartLauncher extends Thread {
 		}
 		catch (Throwable ex) {
 			this.error = ex;
+			getUncaughtExceptionHandler().uncaughtException(this, ex);
 		}
 	}
 

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

@@ -271,10 +271,7 @@ public class Restarter {
 				return;
 			}
 			if (failureHandler.handle(error) == Outcome.ABORT) {
-				if (error instanceof Exception) {
-					throw (Exception) error;
-				}
-				throw new Exception(error);
+				return;
 			}
 		}
 		while (true);

spring-boot/src/main/java/org/springframework/boot/LoggedExceptionHandler.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2012-2015 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.boot;
+
+import java.lang.Thread.UncaughtExceptionHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * {@link UncaughtExceptionHandler} to suppress handling already logged exceptions.
+ *
+ * @author Phillip Webb
+ */
+class LoggedExceptionHandler implements UncaughtExceptionHandler {
+
+	private static LoggedExceptionHandlerThreadLocal handler = new LoggedExceptionHandlerThreadLocal();
+
+	private final UncaughtExceptionHandler parent;
+
+	private final List<Throwable> exceptions = new ArrayList<Throwable>();
+
+	LoggedExceptionHandler(UncaughtExceptionHandler parent) {
+		this.parent = parent;
+	}
+
+	public void register(Throwable exception) {
+		this.exceptions.add(exception);
+	}
+
+	@Override
+	public void uncaughtException(Thread thread, Throwable ex) {
+		if (!isRegistered(ex) && this.parent != null) {
+			this.parent.uncaughtException(thread, ex);
+		}
+	}
+
+	private boolean isRegistered(Throwable ex) {
+		if (this.exceptions.contains(ex)) {
+			return true;
+		}
+		if (ex instanceof InvocationTargetException) {
+			return isRegistered(ex.getCause());
+		}
+		return false;
+	}
+
+	static LoggedExceptionHandler forCurrentThread() {
+		return handler.get();
+	}
+
+	/**
+	 * Thread local used to attach and track handlers.
+	 */
+	private static class LoggedExceptionHandlerThreadLocal
+			extends ThreadLocal<LoggedExceptionHandler> {
+
+		@Override
+		protected LoggedExceptionHandler initialValue() {
+			LoggedExceptionHandler handler = new LoggedExceptionHandler(
+					Thread.currentThread().getUncaughtExceptionHandler());
+			Thread.currentThread().setUncaughtExceptionHandler(handler);
+			return handler;
+		};
+
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/SpringApplication.java

@@ -301,17 +301,8 @@ public class SpringApplication {
 			return context;
 		}
 		catch (Throwable ex) {
-			try {
-				listeners.finished(context, ex);
-				this.log.error("Application startup failed", ex);
-			}
-			finally {
-				if (context != null) {
-					context.close();
-				}
-			}
-			ReflectionUtils.rethrowRuntimeException(ex);
-			return context;
+			handleRunFailure(context, listeners, ex);
+			throw new IllegalStateException(ex);
 		}
 	}
 
@@ -816,6 +807,42 @@ public class SpringApplication {
 	protected void afterRefresh(ConfigurableApplicationContext context, String[] args) {
 	}
 
+	private void handleRunFailure(ConfigurableApplicationContext context,
+			SpringApplicationRunListeners listeners, Throwable exception) {
+		try {
+			try {
+				listeners.finished(context, exception);
+			}
+			finally {
+				if (context != null) {
+					context.close();
+				}
+			}
+		}
+		catch (Exception ex) {
+			this.log.warn("Unable to close ApplicationContext", ex);
+		}
+		if (this.log.isErrorEnabled()) {
+			this.log.error("Application startup failed", exception);
+			registerLoggedException(exception);
+		}
+		ReflectionUtils.rethrowRuntimeException(exception);
+	}
+
+	/**
+	 * Register that the given exception has been logged. By default, if the running in
+	 * the main thread, this method will suppress additional printing of the stacktrace.
+	 * @param exception the exception that was logged
+	 */
+	protected void registerLoggedException(Throwable exception) {
+		Thread currentThread = Thread.currentThread();
+		if (("main".equals(currentThread.getName())
+				|| "restartedMain".equals(currentThread.getName()))
+				&& "main".equals(currentThread.getThreadGroup().getName())) {
+			LoggedExceptionHandler.forCurrentThread().register(exception);
+		}
+	}
+
 	/**
 	 * Set a specific main application class that will be used as a log source and to
 	 * obtain version information. By default the main application class will be deduced.

spring-boot/src/test/java/org/springframework/boot/SpringApplicationTests.java

@@ -697,6 +697,25 @@ public class SpringApplicationTests {
 				.next().getName());
 	}
 
+	@Test
+	public void failureResultsInSingleStackTrace() throws Exception {
+		ThreadGroup group = new ThreadGroup("main");
+		Thread thread = new Thread(group, "main") {
+			@Override
+			public void run() {
+				SpringApplication application = new SpringApplication(
+						FailingConfig.class);
+				application.setWebEnvironment(false);
+				application.run();
+			};
+		};
+		thread.start();
+		thread.join(6000);
+		int occurrences = StringUtils.countOccurrencesOf(this.output.toString(),
+				"Caused by: java.lang.RuntimeException: ExpectedError");
+		assertThat("Expected single stacktrace", occurrences, equalTo(1));
+	}
+
 	private boolean hasPropertySource(ConfigurableEnvironment environment,
 			Class<?> propertySourceClass, String name) {
 		for (PropertySource<?> source : environment.getPropertySources()) {
@@ -810,6 +829,16 @@ public class SpringApplicationTests {
 
 	}
 
+	@Configuration
+	static class FailingConfig {
+
+		@Bean
+		public Object fail() {
+			throw new RuntimeException("ExpectedError");
+		}
+
+	}
+
 	@Configuration
 	static class CommandLineRunConfig {