Fix ordering of mail auto-configuration

It is not possible to put `@Order` on nested `@Configuration` classes and
there is no ordering guarantee of them anyway. Previously, we relied on
the declaration order to check if the `test-connection` flag should apply
to an existing `JavaMailSenderImpl`. It turns out at the
`JavaMailSenderImpl` bean was not created at that time and so the
evaluation was wrongly failing.

To make that more explicit, that code is now in its own
auto-configuration with an explicit `@AutoConfigureAfter` declaration.

Since the JNDI support could be affected by the exact same issue, it has
been restored to its own package private configuration class that is
processed before the  `MailSenderAutoConfiguration` content is evaluated.

Closes gh-3478

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/JndiSessionConfiguration.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.autoconfigure.mail;
+
+import javax.mail.Session;
+import javax.naming.NamingException;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnJndi;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.jndi.JndiLocatorDelegate;
+
+/**
+ * Auto-configure a {@link Session} available on JNDI.
+ *
+ * @author Eddú Meléndez
+ * @author Stephane Nicoll
+ * @since 1.3.0
+ */
+@Configuration
+@ConditionalOnClass(Session.class)
+@ConditionalOnProperty(prefix = "spring.mail", name = "jndi-name")
+@ConditionalOnJndi
+class JndiSessionConfiguration {
+
+	@Autowired
+	private MailProperties properties;
+
+	@Bean
+	@ConditionalOnMissingBean
+	public Session session() {
+		String jndiName = this.properties.getJndiName();
+		try {
+			return new JndiLocatorDelegate().lookup(jndiName, Session.class);
+		}
+		catch (NamingException ex) {
+			throw new IllegalStateException(String.format(
+					"Unable to find Session in JNDI location %s", jndiName), ex);
+		}
+	}
+
+}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/MailSenderAutoConfiguration.java

@@ -18,27 +18,22 @@ package org.springframework.boot.autoconfigure.mail;
 
 import java.util.Map;
 import java.util.Properties;
-
 import javax.activation.MimeType;
-import javax.annotation.PostConstruct;
-import javax.mail.MessagingException;
 import javax.mail.Session;
 import javax.mail.internet.MimeMessage;
-import javax.naming.NamingException;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.AnyNestedCondition;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnJndi;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
+import org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration.MailSenderCondition;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.jndi.JndiLocatorDelegate;
+import org.springframework.context.annotation.Import;
 import org.springframework.mail.MailSender;
 import org.springframework.mail.javamail.JavaMailSenderImpl;
 
@@ -52,37 +47,12 @@ import org.springframework.mail.javamail.JavaMailSenderImpl;
  */
 @Configuration
 @ConditionalOnClass({ MimeMessage.class, MimeType.class })
+@ConditionalOnMissingBean(MailSender.class)
+@Conditional(MailSenderCondition.class)
 @EnableConfigurationProperties(MailProperties.class)
+@Import(JndiSessionConfiguration.class)
 public class MailSenderAutoConfiguration {
 
-	@Configuration
-	@ConditionalOnClass(Session.class)
-	@ConditionalOnProperty(prefix = "spring.mail", name = "jndi-name")
-	@ConditionalOnJndi
-	static class JndiSessionConfiguration {
-
-		@Autowired
-		private MailProperties properties;
-
-		@Bean
-		@ConditionalOnMissingBean
-		public Session session() {
-			String jndiName = this.properties.getJndiName();
-			try {
-				return new JndiLocatorDelegate().lookup(jndiName, Session.class);
-			}
-			catch (NamingException ex) {
-				throw new IllegalStateException(String.format(
-						"Unable to find Session in JNDI location %s", jndiName), ex);
-			}
-		}
-
-	}
-
-	@ConditionalOnMissingBean(MailSender.class)
-	@Conditional(MailSenderConfiguration.MailSenderCondition.class)
-	static class MailSenderConfiguration {
-
 	@Autowired
 	private MailProperties properties;
 
@@ -120,6 +90,7 @@ public class MailSenderAutoConfiguration {
 		return properties;
 	}
 
+
 	/**
 	 * Condition to trigger the creation of a {@link JavaMailSenderImpl}. This kicks
 	 * in if either the host or jndi name property is set.
@@ -139,30 +110,5 @@ public class MailSenderAutoConfiguration {
 		}
 
 	}
-	}
-
-	@Configuration
-	@ConditionalOnSingleCandidate(JavaMailSenderImpl.class)
-	static class MailSenderValidator {
-
-		@Autowired
-		private MailProperties properties;
-
-		@Autowired
-		private JavaMailSenderImpl mailSender;
-
-		@PostConstruct
-		public void validateConnection() {
-			if (this.properties.isTestConnection()) {
-				try {
-					this.mailSender.testConnection();
-				}
-				catch (MessagingException ex) {
-					throw new IllegalStateException("Mail server is not unavailable", ex);
-				}
-			}
-		}
-
-	}
 
 }

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/MailSenderValidatorAutoConfiguration.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.autoconfigure.mail;
+
+import javax.annotation.PostConstruct;
+import javax.mail.MessagingException;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.mail.javamail.JavaMailSenderImpl;
+
+/**
+ * {@link EnableAutoConfiguration Auto configuration} for testing mail service
+ * connectivity on startup.
+ *
+ * @author Eddú Meléndez
+ * @author Stephane Nicoll
+ * @since 1.3.0
+ */
+@Configuration
+@AutoConfigureAfter(MailSenderAutoConfiguration.class)
+@ConditionalOnProperty(prefix = "spring.mail", value = "test-connection")
+@ConditionalOnSingleCandidate(JavaMailSenderImpl.class)
+public class MailSenderValidatorAutoConfiguration {
+
+	@Autowired
+	private JavaMailSenderImpl mailSender;
+
+	@PostConstruct
+	public void validateConnection() {
+		try {
+			this.mailSender.testConnection();
+		}
+		catch (MessagingException ex) {
+			throw new IllegalStateException("Mail server is not unavailable", ex);
+		}
+	}
+
+}

spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -42,6 +42,7 @@ org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
 org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
 org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
 org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
+org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
 org.springframework.boot.autoconfigure.mobile.DeviceResolverAutoConfiguration,\
 org.springframework.boot.autoconfigure.mobile.DeviceDelegatingViewResolverAutoConfiguration,\
 org.springframework.boot.autoconfigure.mobile.SitePreferenceAutoConfiguration,\

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mail/MailSenderAutoConfigurationTests.java

@@ -209,6 +209,7 @@ public class MailSenderAutoConfigurationTests {
 		EnvironmentTestUtils.addEnvironment(applicationContext, environment);
 		applicationContext.register(configs);
 		applicationContext.register(MailSenderAutoConfiguration.class);
+		applicationContext.register(MailSenderValidatorAutoConfiguration.class);
 		applicationContext.refresh();
 		return applicationContext;
 	}