Add Log Output when DevTools restart is disabled

This covers the cases when:
  * An Java agent based reloader (e.g. JRebel) is being used
  * The reloader was disabled by using a system property

See gh-14807

Author: eiselems

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

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.devtools.restart;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.boot.context.event.ApplicationFailedEvent;
 import org.springframework.boot.context.event.ApplicationPreparedEvent;
 import org.springframework.boot.context.event.ApplicationReadyEvent;
@@ -35,10 +38,12 @@
 public class RestartApplicationListener
 		implements ApplicationListener<ApplicationEvent>, Ordered {
 
-	private int order = HIGHEST_PRECEDENCE;
-
 	private static final String ENABLED_PROPERTY = "spring.devtools.restart.enabled";
 
+	private static final Log logger = LogFactory.getLog(RestartApplicationListener.class);
+
+	private int order = HIGHEST_PRECEDENCE;
+
 	@Override
 	public void onApplicationEvent(ApplicationEvent event) {
 		if (event instanceof ApplicationStartingEvent) {
@@ -63,10 +68,17 @@ private void onApplicationStartingEvent(ApplicationStartingEvent event) {
 		if (enabled == null || Boolean.parseBoolean(enabled)) {
 			String[] args = event.getArgs();
 			DefaultRestartInitializer initializer = new DefaultRestartInitializer();
-			boolean restartOnInitialize = !AgentReloader.isActive();
+			boolean restartOnInitialize = true;
+			if (AgentReloader.isActive()) {
+				logger.info(
+						"Restart disabled due to an agent-based reloader being active");
+				restartOnInitialize = false;
+			}
 			Restarter.initialize(args, false, initializer, restartOnInitialize);
 		}
 		else {
+			logger.info("Restart disabled due to System property '" + ENABLED_PROPERTY
+					+ "' set to false");
 			Restarter.disable();
 		}
 	}