Allow spring-boot-devtools to work with JRebel

Update devtools to detect JRebel and disable application restarts. Other
features (such as LiveReload) can still be used.

Fixes gh-3095

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

@@ -105,7 +105,7 @@ public class LocalDevToolsAutoConfiguration {
 		public void onClassPathChanged(ClassPathChangedEvent event) {
 			if (event.isRestartRequired()) {
 				Restarter.getInstance().restart(
-						new FileWatchingFailureHandler(getFileSystemWatcherFactory()));
+						new FileWatchingFailureHandler(fileSystemWatcherFactory()));
 			}
 		}
 
@@ -114,7 +114,7 @@ public class LocalDevToolsAutoConfiguration {
 		public ClassPathFileSystemWatcher classPathFileSystemWatcher() {
 			URL[] urls = Restarter.getInstance().getInitialUrls();
 			ClassPathFileSystemWatcher watcher = new ClassPathFileSystemWatcher(
-					getFileSystemWatcherFactory(), classPathRestartStrategy(), urls);
+					fileSystemWatcherFactory(), classPathRestartStrategy(), urls);
 			watcher.setStopWatcherOnRestart(true);
 			return watcher;
 		}
@@ -127,7 +127,7 @@ public class LocalDevToolsAutoConfiguration {
 		}
 
 		@Bean
-		public FileSystemWatcherFactory getFileSystemWatcherFactory() {
+		public FileSystemWatcherFactory fileSystemWatcherFactory() {
 			return new FileSystemWatcherFactory() {
 
 				@Override

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/classpath/ClassPathFileChangeListener.java

@@ -22,6 +22,7 @@ import org.springframework.boot.devtools.filewatch.ChangedFile;
 import org.springframework.boot.devtools.filewatch.ChangedFiles;
 import org.springframework.boot.devtools.filewatch.FileChangeListener;
 import org.springframework.boot.devtools.filewatch.FileSystemWatcher;
+import org.springframework.boot.devtools.restart.AgentReloader;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.util.Assert;
 
@@ -71,6 +72,9 @@ class ClassPathFileChangeListener implements FileChangeListener {
 	}
 
 	private boolean isRestartRequired(Set<ChangedFiles> changeSet) {
+		if (AgentReloader.isActive()) {
+			return false;
+		}
 		for (ChangedFiles changedFiles : changeSet) {
 			for (ChangedFile changedFile : changedFiles) {
 				if (this.restartStrategy.isRestartRequired(changedFile)) {

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

+/*
+ * 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.devtools.restart;
+
+import org.springframework.util.ClassUtils;
+
+/**
+ * Utility to determine if an Java agent based reloader (e.g. JRebel) is being used.
+ *
+ * @author Phillip Webb
+ * @since 1.3.0
+ */
+public abstract class AgentReloader {
+
+	private AgentReloader() {
+	}
+
+	/**
+	 * Determine if any agent reloader is active.
+	 * @return true if agent reloading is active
+	 */
+	public static boolean isActive() {
+		return isJRebelActive();
+	}
+
+	/**
+	 * Determine if JRebel is active.
+	 * @return true if JRebel is active
+	 */
+	public static boolean isJRebelActive() {
+		return ClassUtils.isPresent("org.zeroturnaround.javarebel.ReloaderFactory", null);
+	}
+
+}

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

@@ -53,7 +53,10 @@ public class RestartApplicationListener implements ApplicationListener<Applicati
 		// users to disable restart using a System property.
 		String enabled = System.getProperty(ENABLED_PROPERTY);
 		if (enabled == null || Boolean.parseBoolean(enabled)) {
-			Restarter.initialize(event.getArgs());
+			String[] args = event.getArgs();
+			DefaultRestartInitializer initializer = new DefaultRestartInitializer();
+			boolean restartOnInitialize = !AgentReloader.isActive();
+			Restarter.initialize(args, false, initializer, restartOnInitialize);
 		}
 		else {
 			Restarter.disable();

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -872,12 +872,16 @@ a very fast feedback loop for code changes. By default, any entry on the classpa
 points to a folder will be monitored for changes.
 
 NOTE: You can also start your application via the supported build plugins (i.e. Maven and
-Gradle) as long as forking is enabled since DevTools need an isolated application classloader
-to operate properly.
+Gradle) as long as forking is enabled since DevTools need an isolated application
+classloader to operate properly.
 
 TIP: Automatic restart works very well when used with LiveReload.
 <<using-boot-devtools-livereload,See below>> for details.
 
+NOTE: If you use JRebel automatic restarts will be disabled in favor of dynamic class
+reloading. Other devtools features (such as LiveReload and property overrides) can still
+be used.
+
 .Restart vs Reload
 ****
 The restart technology provided by Spring Boot works by using two classloaders.