Log condition evaluation delta upon DevTools restart

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

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2012-2017 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.autoconfigure;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.boot.autoconfigure.condition.ConditionEvaluationReport;
+import org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportMessage;
+import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.ApplicationListener;
+
+/**
+ * An {@link ApplicationListener} that logs the delta of condition evaluation across
+ * restarts.
+ *
+ * @author Andy Wilkinson
+ */
+class ConditionEvaluationDeltaLoggingListener
+		implements ApplicationListener<ApplicationReadyEvent> {
+
+	private final Log logger = LogFactory.getLog(getClass());
+
+	private static ConditionEvaluationReport previousReport;
+
+	@Override
+	public void onApplicationEvent(ApplicationReadyEvent event) {
+		ConditionEvaluationReport report = event.getApplicationContext()
+				.getBean(ConditionEvaluationReport.class);
+		if (previousReport != null) {
+			ConditionEvaluationReport delta = report.getDelta(previousReport);
+			if (!delta.getConditionAndOutcomesBySource().isEmpty()
+					|| !delta.getExclusions().isEmpty()
+					|| !delta.getUnconditionalClasses().isEmpty()) {
+				this.logger.info("Condition evaluation delta:"
+						+ new ConditionEvaluationReportMessage(delta,
+								"CONDITION EVALUATION DELTA"));
+			}
+			else {
+				this.logger.info("Condition evaluation unchanged");
+			}
+		}
+		previousReport = report;
+	}
+
+}

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

@@ -100,6 +100,11 @@ public class DevToolsProperties {
 		 */
 		private List<File> additionalPaths = new ArrayList<>();
 
+		/**
+		 * Whether to log the condition evaluation delta upon restart.
+		 */
+		private boolean logConditionEvaluationDelta = true;
+
 		public boolean isEnabled() {
 			return this.enabled;
 		}
@@ -168,6 +173,14 @@ public class DevToolsProperties {
 			this.additionalPaths = additionalPaths;
 		}
 
+		public boolean isLogConditionEvaluationDelta() {
+			return this.logConditionEvaluationDelta;
+		}
+
+		public void setLogConditionEvaluationDelta(boolean logConditionEvaluationDelta) {
+			this.logConditionEvaluationDelta = logConditionEvaluationDelta;
+		}
+
 	}
 
 	/**

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

@@ -140,6 +140,12 @@ public class LocalDevToolsAutoConfiguration {
 			return this::newFileSystemWatcher;
 		}
 
+		@Bean
+		@ConditionalOnProperty(prefix = "spring.devtools.restart", name = "log-condition-evaluation-delta", matchIfMissing = true)
+		public ConditionEvaluationDeltaLoggingListener conditionEvaluationDeltaLoggingListener() {
+			return new ConditionEvaluationDeltaLoggingListener();
+		}
+
 		private FileSystemWatcher newFileSystemWatcher() {
 			Restart restartProperties = this.properties.getRestart();
 			FileSystemWatcher watcher = new FileSystemWatcher(true,