#bbottema/simple-java-mail#430: reconnect disconnected Transport inst…

…ances when being claimed for imminent reuse.

src/main/java/org/simplejavamail/smtpconnectionpool/TransportAllocator.java

@@ -1,10 +1,7 @@
 package org.simplejavamail.smtpconnectionpool;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
-import jakarta.mail.MessagingException;
-import jakarta.mail.NoSuchProviderException;
-import jakarta.mail.Session;
-import jakarta.mail.Transport;
+import jakarta.mail.*;
 import lombok.val;
 import org.bbottema.genericobjectpool.Allocator;
 import org.jetbrains.annotations.NotNull;
@@ -30,26 +27,35 @@ public Transport allocate() {
 		LOGGER.trace("opening transport connection...");
 		try {
 			Transport transport = session.getTransport();
-			connectTransport(transport, session);
+			connectTransport(transport);
 			return transport;
 		} catch (NoSuchProviderException e) {
 			throw new TransportHandlingException("unable to get transport from session:\n\t" + session.getProperties(), e);
-		} catch (MessagingException e) {
-			throw new TransportHandlingException("Error when trying to open connection to the server, session:\n\t" + session.getProperties(), e);
 		}
 	}
 
-	private static void connectTransport(Transport transport, Session session) throws MessagingException {
-		val oauth2Token = (String) session.getProperties().getOrDefault(OAUTH2_TOKEN_PROPERTY, null);
-		if (oauth2Token != null) {
-			/*
-			 * To connect using OAuth2 authentication, we need to connect slightly differently as we can't use only Session properties and the traditional Authenticator class for
-			 * providing password. Instead, <em>mail.smtp.auth</em> is set to {@code false} and the OAuth2 authenticator should take over, but this is only triggered succesfully if we
-			 * provide an empty non-null password, which is only possible using the alternative {@link Transport#connect(String, String)}.
-			 */
-			transport.connect(session.getProperties().getProperty("mail.smtp.user"), oauth2Token);
-		} else {
-			transport.connect();
+	@Override
+	public void allocateForReuse(Transport transport) {
+		if (!transport.isConnected()) {
+			connectTransport(transport);
+		}
+	}
+
+	private void connectTransport(Transport transport) {
+		try {
+			val oauth2Token = (String) session.getProperties().getOrDefault(OAUTH2_TOKEN_PROPERTY, null);
+			if (oauth2Token != null) {
+				/*
+				 * To connect using OAuth2 authentication, we need to connect slightly differently as we can't use only Session properties and the traditional Authenticator class for
+				 * providing password. Instead, <em>mail.smtp.auth</em> is set to {@code false} and the OAuth2 authenticator should take over, but this is only triggered succesfully if we
+				 * provide an empty non-null password, which is only possible using the alternative {@link Transport#connect(String, String)}.
+				 */
+				transport.connect(session.getProperties().getProperty("mail.smtp.user"), oauth2Token);
+			} else {
+				transport.connect();
+			}
+		} catch (MessagingException e) {
+			throw new TransportHandlingException("Error when trying to open connection to the server, session:\n\t" + session.getProperties(), e);
 		}
 	}