#121: added support for a user provided custom mailer implementation

modules/core-module/src/main/java/org/simplejavamail/api/mailer/CustomMailer.java

@@ -0,0 +1,22 @@
+package org.simplejavamail.api.mailer;
+
+import org.simplejavamail.api.email.Email;
+import org.simplejavamail.api.mailer.config.OperationalConfig;
+
+import javax.annotation.Nonnull;
+import javax.mail.Session;
+import javax.mail.internet.MimeMessage;
+
+/**
+ * By default, Simple Java Mail handles the ultimate connection and sending of emails. However, it is possible to replace this last step
+ * by a custom implementation.
+ * <p>
+ * The benefit of this is that Simple Java Mail acts as an accelarator, providing thread pool, applying email content-validation, address validations,
+ * configuring a {@code Session} instance, producing a {@code MimeMessage}, all with full S/MIME, DKIM support and everything else.
+ *
+ * @see MailerGenericBuilder#withCustomMailer(CustomMailer)
+ */
+public interface CustomMailer {
+	void testConnection(@Nonnull OperationalConfig operationalConfig, @Nonnull Session session);
+	void sendMessage(@Nonnull OperationalConfig operationalConfig, @Nonnull Session session, final Email email, @Nonnull MimeMessage message);
+}

modules/core-module/src/main/java/org/simplejavamail/api/mailer/MailerGenericBuilder.java

@@ -419,6 +419,11 @@ public interface MailerGenericBuilder<T extends MailerGenericBuilder<?>> {
 	 */
 	T withProperty(@Nonnull String propertyName, @Nullable Object propertyValue);
 
+	/**
+	 * @see CustomMailer
+	 */
+	T withCustomMailer(@Nonnull CustomMailer customMailer);
+
 	/**
 	 * Resets session time to its default ({@value DEFAULT_SESSION_TIMEOUT_MILLIS}).
 	 *
@@ -705,4 +710,10 @@ public interface MailerGenericBuilder<T extends MailerGenericBuilder<?>> {
 	 */
 	@Nullable
 	Properties getProperties();
+
+	/**
+	 * @see #withCustomMailer(CustomMailer)
+	 */
+	@Nullable
+	CustomMailer getCustomMailer();
 }

modules/core-module/src/main/java/org/simplejavamail/api/mailer/config/OperationalConfig.java

@@ -1,10 +1,12 @@
 package org.simplejavamail.api.mailer.config;
 
+import org.simplejavamail.api.mailer.CustomMailer;
 import org.simplejavamail.api.mailer.Mailer;
 import org.simplejavamail.api.mailer.MailerGenericBuilder;
 import org.simplejavamail.api.mailer.MailerRegularBuilder;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Properties;
 import java.util.UUID;
@@ -95,15 +97,21 @@ public interface OperationalConfig {
 	@Nonnull
 	Properties getProperties();
 
+	/**
+	 * @see MailerGenericBuilder#withClusterKey(UUID)
+	 */
+	@Nonnull
+	UUID getClusterKey();
+
 	/**
 	 * @see MailerGenericBuilder#withExecutorService(ExecutorService)
 	 */
 	@Nonnull
 	ExecutorService getExecutorService();
 
 	/**
-	 * @see MailerGenericBuilder#withClusterKey(UUID)
+	 * @see MailerGenericBuilder#withCustomMailer(CustomMailer)
 	 */
-	@Nonnull
-	UUID getClusterKey();
+	@Nullable
+	CustomMailer getCustomMailer();
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/MailerGenericBuilderImpl.java

@@ -1,13 +1,13 @@
 package org.simplejavamail.mailer.internal;
 
 import org.hazlewood.connor.bottema.emailaddress.EmailAddressCriteria;
+import org.simplejavamail.api.mailer.CustomMailer;
 import org.simplejavamail.api.mailer.MailerGenericBuilder;
 import org.simplejavamail.api.mailer.config.LoadBalancingStrategy;
 import org.simplejavamail.api.mailer.config.OperationalConfig;
 import org.simplejavamail.api.mailer.config.ProxyConfig;
 import org.simplejavamail.config.ConfigLoader.Property;
 import org.simplejavamail.internal.modules.ModuleLoader;
-import org.simplejavamail.internal.util.SimpleOptional;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -169,6 +169,12 @@ abstract class MailerGenericBuilderImpl<T extends MailerGenericBuilderImpl<?>> i
 	 * @see MailerGenericBuilder#withTransportModeLoggingOnly(Boolean)
 	 */
 	private boolean transportModeLoggingOnly;
+
+	/**
+	 * @see MailerGenericBuilder#withCustomMailer(CustomMailer)
+	 */
+	@Nullable
+	private CustomMailer customMailer;
 
 	/**
 	 * Sets defaults configured for proxy host, proxy port, proxy username, proxy password and proxy bridge port (used in authenticated proxy).
@@ -259,7 +265,8 @@ OperationalConfig buildOperationalConfig() {
 				getSslHostsToTrust(),
 				isTrustAllSSLHost(),
 				isVerifyingServerIdentity(),
-				getExecutorService());
+				getExecutorService(),
+				getCustomMailer());
 	}
 
 	/**
@@ -515,6 +522,15 @@ public T withProperty(@Nonnull final String propertyName, @Nullable final Object
 		return (T) this;
 	}
 
+	/**
+	 * @see MailerGenericBuilder#withCustomMailer(CustomMailer)
+	 */
+	@Override
+	public T withCustomMailer(@Nonnull CustomMailer customMailer) {
+		this.customMailer = customMailer;
+		return (T) this;
+	}
+
 	/**
 	 * @see MailerGenericBuilder#resetSessionTimeout()
 	 */
@@ -870,4 +886,13 @@ public boolean isTransportModeLoggingOnly() {
 	public Properties getProperties() {
 		return properties;
 	}
+
+	/**
+	 * @see MailerGenericBuilder#getCustomMailer()
+	 */
+	@Override
+	@Nullable
+	public CustomMailer getCustomMailer() {
+		return customMailer;
+	}
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/MailerImpl.java

@@ -118,7 +118,7 @@ public class MailerImpl implements Mailer {
 		this.session = session;
 		this.operationalConfig = operationalConfig;
 		final TransportStrategy effectiveTransportStrategy = ofNullable(transportStrategy).orMaybe(findStrategyForSession(session));
-		this.proxyServer = configureSessionWithProxy(proxyConfig, session, effectiveTransportStrategy);
+		this.proxyServer = configureSessionWithProxy(proxyConfig, operationalConfig, session, effectiveTransportStrategy);
 		initSession(session, operationalConfig, effectiveTransportStrategy);
 		initCluster(session, operationalConfig);
 	}
@@ -227,10 +227,14 @@ private void configureServerIdentityVerification(@Nonnull final Session session,
 	 * @return null in case of no proxy or anonymous proxy, or a AnonymousSocks5Server proxy bridging server instance in case of authenticated proxy.
 	 */
 	@Nullable
-	private static AnonymousSocks5Server configureSessionWithProxy(@Nonnull final ProxyConfig proxyConfig,
+	private static AnonymousSocks5Server configureSessionWithProxy(
+			@Nonnull final ProxyConfig proxyConfig,
+			@Nonnull final OperationalConfig operationalConfig,
 			@Nonnull final Session session,
 			@Nullable final TransportStrategy transportStrategy) {
-		if (!proxyConfig.requiresProxy()) {
+		if (operationalConfig.getCustomMailer() != null) {
+			LOGGER.trace("CustomMailer provided by user, skipping proxy.");
+		} else if (!proxyConfig.requiresProxy()) {
 			LOGGER.trace("No proxy set, skipping proxy.");
 		} else {
 			if (transportStrategy == TransportStrategy.SMTPS) {
@@ -260,7 +264,7 @@ private static AnonymousSocks5Server configureSessionWithProxy(@Nonnull final Pr
 	}
 
 	private void initCluster(@Nonnull final Session session, @Nonnull final OperationalConfig operationalConfig) {
-		if (ModuleLoader.batchModuleAvailable()) {
+		if (operationalConfig.getCustomMailer() == null && ModuleLoader.batchModuleAvailable()) {
 			ModuleLoader.loadBatchModule().registerToCluster(operationalConfig, operationalConfig.getClusterKey(), session);
 		}
 	}
@@ -278,7 +282,7 @@ public void testConnection() {
 	 */
 	@Nullable
 	public synchronized AsyncResponse testConnection(boolean async) {
-		TestConnectionClosure testConnectionClosure = new TestConnectionClosure(operationalConfig.getClusterKey(), session, proxyServer, async, smtpConnectionCounter);
+		TestConnectionClosure testConnectionClosure = new TestConnectionClosure(operationalConfig, session, proxyServer, async, smtpConnectionCounter);
 
 		if (!async) {
 			testConnectionClosure.run();
@@ -304,7 +308,7 @@ public final void sendMail(final Email email) {
 	@Nullable
 	public final AsyncResponse sendMail(final Email email, @SuppressWarnings("SameParameterValue") final boolean async) {
 		if (validate(email)) {
-			SendMailClosure sendMailClosure = new SendMailClosure(operationalConfig.getClusterKey(), session, email, proxyServer, async, operationalConfig.isTransportModeLoggingOnly(),
+			SendMailClosure sendMailClosure = new SendMailClosure(operationalConfig, session, email, proxyServer, async, operationalConfig.isTransportModeLoggingOnly(),
 					smtpConnectionCounter);
 
 			if (!async) {

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/OperationalConfigImpl.java

@@ -1,9 +1,11 @@
 package org.simplejavamail.mailer.internal;
 
+import org.simplejavamail.api.mailer.CustomMailer;
 import org.simplejavamail.api.mailer.config.LoadBalancingStrategy;
 import org.simplejavamail.api.mailer.config.OperationalConfig;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.Collections;
 import java.util.List;
 import java.util.Properties;
@@ -104,9 +106,15 @@ class OperationalConfigImpl implements OperationalConfig {
 	 */
 	@Nonnull
 	private final ExecutorService executorService;
+
+	/**
+	 * @see org.simplejavamail.api.mailer.MailerGenericBuilder#withCustomMailer(CustomMailer)
+	 */
+	@Nullable
+	private final CustomMailer customMailer;
 
 	OperationalConfigImpl(final boolean async,
-			final Properties properties,
+			@Nullable final Properties properties,
 			final int sessionTimeout,
 			final int threadPoolSize,
 			final int threadPoolKeepAliveTime,
@@ -121,7 +129,8 @@ class OperationalConfigImpl implements OperationalConfig {
 			@Nonnull final List<String> sslHostsToTrust,
 			final boolean trustAllSSLHost,
 			final boolean verifyingServerIdentity,
-			@Nonnull final ExecutorService executorService) {
+			@Nonnull final ExecutorService executorService,
+			@Nullable final CustomMailer customMailer) {
 		this.async = async; // can be overridden when calling {@code mailer.send(async = true)}
 		this.properties = properties;
 		this.sessionTimeout = sessionTimeout;
@@ -139,6 +148,30 @@ class OperationalConfigImpl implements OperationalConfig {
 		this.trustAllSSLHost = trustAllSSLHost;
 		this.verifyingServerIdentity = verifyingServerIdentity;
 		this.executorService = executorService;
+		this.customMailer = customMailer;
+	}
+
+	@Override
+	public String toString() {
+		return "OperationalConfigImpl{" + "async=" + async
+				+ ", properties=" + properties
+				+ ", sessionTimeout=" + sessionTimeout
+				+ ", threadPoolSize=" + threadPoolSize
+				+ ", threadPoolKeepAliveTime=" + threadPoolKeepAliveTime
+				+ ", clusterKey=" + clusterKey
+				+ ", connectionPoolCoreSize=" + connectionPoolCoreSize
+				+ ", connectionPoolMaxSize=" + connectionPoolMaxSize
+				+ ", connectionPoolClaimTimeoutMillis=" + connectionPoolClaimTimeoutMillis
+				+ ", connectionPoolExpireAfterMillis=" + connectionPoolExpireAfterMillis
+				+ ", connectionPoolLoadBalancingStrategy=" + connectionPoolLoadBalancingStrategy
+				+ ", transportModeLoggingOnly=" + transportModeLoggingOnly
+				+ ", debugLogging=" + debugLogging
+				+ ", sslHostsToTrust=" + sslHostsToTrust
+				+ ", trustAllSSLHost=" + trustAllSSLHost
+				+ ", verifyingServerIdentity=" + verifyingServerIdentity
+				+ ", executorService=" + executorService
+				+ ", customMailer=" + customMailer
+				+ '}';
 	}
 
 	/**
@@ -264,15 +297,21 @@ public Properties getProperties() {
 		return properties;
 	}
 
+	@Nonnull
+	@Override
+	public UUID getClusterKey() {
+		return clusterKey;
+	}
+
 	@Nonnull
 	@Override
 	public ExecutorService getExecutorService() {
 		return executorService;
 	}
 
-	@Nonnull
+	@Nullable
 	@Override
-	public UUID getClusterKey() {
-		return clusterKey;
+	public CustomMailer getCustomMailer() {
+		return customMailer;
 	}
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/SendMailClosure.java

@@ -2,6 +2,7 @@
 
 import org.simplejavamail.api.email.Email;
 import org.simplejavamail.api.internal.authenticatedsockssupport.socks5server.AnonymousSocks5Server;
+import org.simplejavamail.api.mailer.config.OperationalConfig;
 import org.simplejavamail.converter.internal.mimemessage.MimeMessageProducerHelper;
 import org.simplejavamail.mailer.internal.util.SessionLogger;
 import org.simplejavamail.mailer.internal.util.TransportRunner;
@@ -12,7 +13,6 @@
 import javax.mail.Session;
 import javax.mail.internet.MimeMessage;
 import java.io.UnsupportedEncodingException;
-import java.util.UUID;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.simplejavamail.converter.EmailConverter.mimeMessageToEML;
@@ -25,17 +25,18 @@
  */
 class SendMailClosure extends AbstractProxyServerSyncingClosure {
 
-	@Nonnull private final UUID clusterKey;
+	@Nonnull private final OperationalConfig operationalConfig;
 	@Nonnull private final Session session;
 	@Nonnull private final Email email;
 	private final boolean asyncForLoggingPurpose;
 	private final boolean transportModeLoggingOnly;
 
-	SendMailClosure(@Nonnull UUID clusterKey, @Nonnull Session session, @Nonnull Email email, @Nullable AnonymousSocks5Server proxyServer, boolean asyncForLoggingPurpose, boolean transportModeLoggingOnly, @Nonnull AtomicInteger smtpConnectionCounter) {
+	SendMailClosure(@Nonnull OperationalConfig operationalConfig, @Nonnull Session session, @Nonnull Email email, @Nullable AnonymousSocks5Server proxyServer, boolean asyncForLoggingPurpose,
+			boolean transportModeLoggingOnly, @Nonnull AtomicInteger smtpConnectionCounter) {
 		super(smtpConnectionCounter, proxyServer);
+		this.operationalConfig = operationalConfig;
 		this.session = session;
 		this.email = email;
-		this.clusterKey = clusterKey;
 		this.asyncForLoggingPurpose = asyncForLoggingPurpose;
 		this.transportModeLoggingOnly = transportModeLoggingOnly;
 	}
@@ -56,8 +57,10 @@ public void executeClosure() {
 
 			if (transportModeLoggingOnly) {
 				LOGGER.info("TRANSPORT_MODE_LOGGING_ONLY: skipping actual sending...");
+			} else if (operationalConfig.getCustomMailer() != null) {
+				operationalConfig.getCustomMailer().sendMessage(operationalConfig, session, email, message);
 			} else {
-				TransportRunner.sendMessage(clusterKey, session, message, message.getAllRecipients());
+				TransportRunner.sendMessage(operationalConfig.getClusterKey(), session, message, message.getAllRecipients());
 			}
 		} catch (final UnsupportedEncodingException e) {
 			LOGGER.error("Failed to send email:\n{}", email);