Allow additional paths that trigger a reload/restart to be configured

Previously, only folders on the classpath would be watched and used
to trigger a restart/reload of the application. This commit adds a
new property spring.devtools.restart.additional-paths that can be
used to configure additional paths that should be watched for
changes. When a change occurs in one of those paths a restart or
reload will be triggered, depending on the full restart exclude
patterns configured via the existing spring.devtools.restart.exclude
property.

Closes gh-3469

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

@@ -16,6 +16,10 @@
 
 package org.springframework.boot.devtools.autoconfigure;
 
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.NestedConfigurationProperty;
 
@@ -87,6 +91,11 @@ public class DevToolsProperties {
 		 */
 		private String triggerFile;
 
+		/**
+		 * Additional paths to watch for changes.
+		 */
+		private List<File> additionalPaths = new ArrayList<File>();
+
 		public boolean isEnabled() {
 			return this.enabled;
 		}
@@ -127,6 +136,14 @@ public class DevToolsProperties {
 			this.triggerFile = triggerFile;
 		}
 
+		public List<File> getAdditionalPaths() {
+			return this.additionalPaths;
+		}
+
+		public void setAdditionalPaths(List<File> additionalPaths) {
+			this.additionalPaths = additionalPaths;
+		}
+
 	}
 
 	/**

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

@@ -16,7 +16,9 @@
 
 package org.springframework.boot.devtools.autoconfigure;
 
+import java.io.File;
 import java.net.URL;
+import java.util.List;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -158,6 +160,10 @@ public class LocalDevToolsAutoConfiguration {
 			if (StringUtils.hasLength(triggerFile)) {
 				watcher.setTriggerFilter(new TriggerFileFilter(triggerFile));
 			}
+			List<File> additionalPaths = restartProperties.getAdditionalPaths();
+			for (File path : additionalPaths) {
+				watcher.addSourceFolder(path.getAbsoluteFile());
+			}
 			return watcher;
 		}