Add mail health check

Define an additional health indicator for each JavaMailSenderImpl
instance in the context.

Closes gh-2017 and gh-2617

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/autoconfigure/HealthIndicatorAutoConfiguration.java

@@ -32,6 +32,7 @@ import org.springframework.boot.actuate.health.DiskSpaceHealthIndicator;
 import org.springframework.boot.actuate.health.DiskSpaceHealthIndicatorProperties;
 import org.springframework.boot.actuate.health.HealthAggregator;
 import org.springframework.boot.actuate.health.HealthIndicator;
+import org.springframework.boot.actuate.health.MailHealthIndicator;
 import org.springframework.boot.actuate.health.MongoHealthIndicator;
 import org.springframework.boot.actuate.health.OrderedHealthAggregator;
 import org.springframework.boot.actuate.health.RabbitHealthIndicator;
@@ -48,6 +49,7 @@ import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
 import org.springframework.boot.autoconfigure.jdbc.metadata.DataSourcePoolMetadata;
 import org.springframework.boot.autoconfigure.jdbc.metadata.DataSourcePoolMetadataProvider;
 import org.springframework.boot.autoconfigure.jdbc.metadata.DataSourcePoolMetadataProviders;
+import org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration;
 import org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration;
 import org.springframework.boot.autoconfigure.mongo.MongoDataAutoConfiguration;
 import org.springframework.boot.autoconfigure.redis.RedisAutoConfiguration;
@@ -57,6 +59,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.mongodb.core.MongoTemplate;
 import org.springframework.data.redis.connection.RedisConnectionFactory;
+import org.springframework.mail.javamail.JavaMailSenderImpl;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for {@link HealthIndicator}s.
@@ -70,7 +73,8 @@ import org.springframework.data.redis.connection.RedisConnectionFactory;
 @AutoConfigureBefore({ EndpointAutoConfiguration.class })
 @AutoConfigureAfter({ DataSourceAutoConfiguration.class, MongoAutoConfiguration.class,
 		MongoDataAutoConfiguration.class, RedisAutoConfiguration.class,
-		RabbitAutoConfiguration.class, SolrAutoConfiguration.class })
+		RabbitAutoConfiguration.class, SolrAutoConfiguration.class,
+		MailSenderAutoConfiguration.class })
 @EnableConfigurationProperties({ HealthIndicatorAutoConfigurationProperties.class })
 public class HealthIndicatorAutoConfiguration {
 
@@ -276,4 +280,40 @@ public class HealthIndicatorAutoConfiguration {
 
 	}
 
+	@Configuration
+	@ConditionalOnBean(JavaMailSenderImpl.class)
+	@ConditionalOnProperty(prefix = "management.health.mail", name = "enabled", matchIfMissing = true)
+	public static class MailHealthIndicatorConfiguration {
+
+		@Autowired
+		private HealthAggregator healthAggregator;
+
+		@Autowired(required = false)
+		private Map<String, JavaMailSenderImpl> mailSenders;
+
+		@Bean
+		@ConditionalOnMissingBean(name = "mailSenderHealthIndicator")
+		public HealthIndicator mailHealthIndicator() {
+			if (this.mailSenders.size() == 1) {
+				JavaMailSenderImpl mailSender = this.mailSenders.values().iterator()
+						.next();
+				return createMailHealthIndicator(mailSender);
+			}
+			CompositeHealthIndicator composite = new CompositeHealthIndicator(
+					this.healthAggregator);
+			for (Map.Entry<String, JavaMailSenderImpl> entry : this.mailSenders
+					.entrySet()) {
+				String name = entry.getKey();
+				JavaMailSenderImpl mailSender = entry.getValue();
+				composite.addHealthIndicator(name, createMailHealthIndicator(mailSender));
+			}
+			return composite;
+		}
+
+		private MailHealthIndicator createMailHealthIndicator(
+				JavaMailSenderImpl mailSender) {
+			return new MailHealthIndicator(mailSender);
+		}
+	}
+
 }

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/MailHealthIndicator.java

@@ -0,0 +1,86 @@
+/*
+ * 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.actuate.health;
+
+import javax.mail.MessagingException;
+import javax.mail.NoSuchProviderException;
+import javax.mail.Session;
+import javax.mail.Transport;
+
+import org.springframework.boot.actuate.health.Health.Builder;
+import org.springframework.mail.javamail.JavaMailSenderImpl;
+
+/**
+ * {@link HealthIndicator} for configured smtp server(s).
+ *
+ * @author Johannes Stelzer
+ * @since 1.3.0
+ */
+public class MailHealthIndicator extends AbstractHealthIndicator {
+
+	private final JavaMailSenderImpl mailSender;
+
+	public MailHealthIndicator(JavaMailSenderImpl mailSender) {
+		this.mailSender = mailSender;
+	}
+
+	@Override
+	protected void doHealthCheck(Builder builder) throws Exception {
+		String location = String.format("%s:%d", this.mailSender.getHost(), this.mailSender.getPort());
+		builder.withDetail("location", location);
+
+		Transport transport = null;
+		try {
+			transport = connectTransport();
+			builder.up();
+		}
+		finally {
+			if (transport != null) {
+				transport.close();
+			}
+		}
+	}
+
+	// Copy-paste from JavaMailSenderImpl - see SPR-12799
+	private Transport connectTransport() throws MessagingException {
+		String username = this.mailSender.getUsername();
+		String password = this.mailSender.getPassword();
+		if ("".equals(username)) {
+			username = null;
+			if ("".equals(password)) {
+				password = null;
+			}
+		}
+
+		Transport transport = getTransport(this.mailSender.getSession());
+		transport.connect(this.mailSender.getHost(), this.mailSender.getPort(), username,
+				password);
+		return transport;
+	}
+
+	private Transport getTransport(Session session) throws NoSuchProviderException {
+		String protocol = this.mailSender.getProtocol();
+		if (protocol == null) {
+			protocol = session.getProperty("mail.transport.protocol");
+			if (protocol == null) {
+				protocol = JavaMailSenderImpl.DEFAULT_PROTOCOL;
+			}
+		}
+		return session.getTransport(protocol);
+	}
+
+}

spring-boot-actuator/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -58,6 +58,12 @@
     "description": "Enable Solr health check.",
     "defaultValue": true
   },
+  {
+    "name": "management.health.mail.enabled",
+    "type": "java.lang.Boolean",
+    "description": "Enable Mail health check.",
+    "defaultValue": true
+  },
   {
     "name": "spring.git.properties",
     "type": "java.lang.String",