#465: don't explicitly depend on DKIM/SMIME modules

Author: bbottema

modules/core-module/src/main/java/org/simplejavamail/internal/modules/DKIMModule.java

@@ -25,4 +25,11 @@ public interface DKIMModule {
 	 * @return The original mime message wrapped in a new one that performs signing when sent.
 	 */
 	MimeMessage signMessageWithDKIM(@NotNull Email email, @NotNull MimeMessage messageToSign, @NotNull DkimConfig dkimConfig, @NotNull Recipient fromRecipient);
+
+	/**
+	 * @return Whether the email has been properly wrapped in a MimeMessage subtype that overrides Message-ID. This is to
+	 * make sure we never send an email without making sure the Message-ID is properly customized (using
+	 * {@link org.simplejavamail.api.email.EmailPopulatingBuilder#fixingMessageId(String)}.
+	 */
+    boolean isMessageIdFixingMessage(MimeMessage message);
 }

modules/core-module/src/main/java/org/simplejavamail/internal/modules/SMIMEModule.java

@@ -74,4 +74,11 @@ public interface SMIMEModule {
 
 	@NotNull
 	MimeMessage encryptMessageWithSmime(@NotNull Session session, @NotNull final Email email, @NotNull MimeMessage messageToProtect, @NotNull X509Certificate x509Certificate);
+
+	/**
+	 * @return Whether the email has been properly wrapped in a MimeMessage subtype that overrides Message-ID. This is to
+	 * make sure we never send an email without making sure the Message-ID is properly customized (using
+	 * {@link org.simplejavamail.api.email.EmailPopulatingBuilder#fixingMessageId(String)}.
+	 */
+    boolean isMessageIdFixingMessage(MimeMessage message);
 }

modules/dkim-module/src/main/java/org/simplejavamail/internal/dkimsupport/DKIMSigner.java

@@ -57,4 +57,9 @@ public MimeMessage signMessageWithDKIM(@NotNull Email email, @NotNull final Mime
 			throw new org.simplejavamail.internal.dkimsupport.DKIMSigningException(org.simplejavamail.internal.dkimsupport.DKIMSigningException.ERROR_SIGNING_DKIM_INVALID_DOMAINKEY, e);
 		}
 	}
+
+	@Override
+	public boolean isMessageIdFixingMessage(MimeMessage message) {
+		return message instanceof DkimMessageIdFixingMimeMessage;
+	}
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/internal/moduleloader/ModuleLoader.java

@@ -18,6 +18,7 @@ public class ModuleLoader {
 
 	private static final boolean BATCH_SUPPORT_CLASS_AVAILABLE = MiscUtil.classAvailable("org.simplejavamail.internal.batchsupport.BatchSupport");
 	private static final boolean SMIME_SUPPORT_CLASS_AVAILABLE = MiscUtil.classAvailable("org.simplejavamail.internal.smimesupport.SMIMESupport");
+	private static final boolean DKIM_SUPPORT_CLASS_AVAILABLE = MiscUtil.classAvailable("org.simplejavamail.internal.dkimsupport.DKIMSigner");
 
 	private static final Map<Class, Object> LOADED_MODULES = new HashMap<>();
 
@@ -100,6 +101,13 @@ public static boolean smimeModuleAvailable() {
 						SMIME_SUPPORT_CLASS_AVAILABLE);
 	}
 
+	public static boolean dkimModuleAvailable() {
+		return !FORCED_DISABLED_MODULES.contains(DKIMModule.class) &&
+				((FORCED_RECHECK_MODULES.contains(DKIMModule.class) &&
+						MiscUtil.classAvailable("org.simplejavamail.internal.dkimsupport.DKIMSigner")) ||
+						DKIM_SUPPORT_CLASS_AVAILABLE);
+	}
+
 	@SuppressWarnings("unchecked")
 	private static <T> T loadModule(Class moduleClass,String moduleName, String moduleImplClassName, String moduleHome) {
 		try {

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

@@ -15,11 +15,9 @@
 import org.simplejavamail.converter.internal.mimemessage.ImmutableDelegatingSMTPMessage;
 import org.simplejavamail.converter.internal.mimemessage.MimeMessageProducerHelper;
 import org.simplejavamail.email.internal.InternalEmail;
-import org.simplejavamail.internal.dkimsupport.DkimMessageIdFixingMimeMessage;
+import org.simplejavamail.internal.moduleloader.ModuleLoader;
 import org.simplejavamail.mailer.internal.util.MessageIdFixingMimeMessage;
 import org.simplejavamail.mailer.internal.util.SessionLogger;
-import org.simplejavamail.utils.mail.smime.SmimeMessageIdFixingMimeMessage;
-import org.simplejavamail.utils.mail.smime.SmimeMessageIdFixingSMTPMessage;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -90,12 +88,8 @@ private MimeMessage convertAndLogMimeMessage(final Email email) throws Messaging
 
         SessionLogger.logSession(session, operationalConfig.isAsync(), "mail");
 
-        if (!(message instanceof MessageIdFixingMimeMessage) &&
-                !(message instanceof DkimMessageIdFixingMimeMessage) &&
-                !(message instanceof ImmutableDelegatingSMTPMessage) &&
-                !(message instanceof SmimeMessageIdFixingMimeMessage) &&
-                !(message instanceof SmimeMessageIdFixingSMTPMessage)) {
-            throw new AssertionError("Wrong MimeMessage type; will be unable to fix Message-ID on message.saveChanges()");
+        if (!messageIsProperlyWrappedForCustomMessageId(message)) {
+            throw new AssertionError("Wrong MimeMessage type; would be unable to fix Message-ID on message.saveChanges()");
         }
 
         message.saveChanges(); // some headers and id's will be set for this specific message
@@ -107,6 +101,12 @@ private MimeMessage convertAndLogMimeMessage(final Email email) throws Messaging
         return message;
     }
 
+    private static boolean messageIsProperlyWrappedForCustomMessageId(MimeMessage message) {
+        return message instanceof MessageIdFixingMimeMessage || message instanceof ImmutableDelegatingSMTPMessage ||
+                (ModuleLoader.dkimModuleAvailable() && ModuleLoader.loadDKIMModule().isMessageIdFixingMessage(message)) ||
+                (ModuleLoader.smimeModuleAvailable() && ModuleLoader.loadSmimeModule().isMessageIdFixingMessage(message));
+    }
+
     static private MimeMessage convertMimeMessage(final Email email, final Session session) throws MessagingException {
         try {
             return MimeMessageProducerHelper.produceMimeMessage(email, session);

modules/smime-module/src/main/java/org/simplejavamail/internal/smimesupport/SMIMESupport.java

@@ -45,6 +45,8 @@
 import org.simplejavamail.internal.smimesupport.model.SmimeDetailsImpl;
 import org.simplejavamail.utils.mail.smime.SmimeKey;
 import org.simplejavamail.utils.mail.smime.SmimeKeyStore;
+import org.simplejavamail.utils.mail.smime.SmimeMessageIdFixingMimeMessage;
+import org.simplejavamail.utils.mail.smime.SmimeMessageIdFixingSMTPMessage;
 import org.simplejavamail.utils.mail.smime.SmimeState;
 import org.simplejavamail.utils.mail.smime.SmimeUtil;
 import org.slf4j.Logger;
@@ -447,6 +449,11 @@ public MimeMessage encryptMessageWithSmime(@Nullable final Session session, @Not
 		return SmimeUtil.encrypt(session, email.getId(), messageToProtect, x509Certificate);
 	}
 
+	@Override
+	public boolean isMessageIdFixingMessage(MimeMessage message) {
+		return message instanceof SmimeMessageIdFixingMimeMessage || message instanceof SmimeMessageIdFixingSMTPMessage;
+	}
+
 	private SmimeKey retrieveSmimeKeyFromPkcs12Keystore(@NotNull Pkcs12Config pkcs12) {
 		if (!SIMPLE_SMIMESTORE_CACHE.containsKey(pkcs12)) {
 			SIMPLE_SMIMESTORE_CACHE.put(pkcs12, produceSmimeKey(pkcs12));