Review nullability of spring-ws-support

See gh-1562

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/JmsMessageReceiver.java

@@ -20,6 +20,7 @@ import jakarta.jms.BytesMessage;
 import jakarta.jms.Message;
 import jakarta.jms.Session;
 import jakarta.jms.TextMessage;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.jms.core.MessagePostProcessor;
 import org.springframework.ws.transport.WebServiceMessageReceiver;
@@ -44,7 +45,7 @@ public class JmsMessageReceiver extends SimpleWebServiceMessageReceiverObjectSup
 
 	private String textMessageEncoding = DEFAULT_TEXT_MESSAGE_ENCODING;
 
-	private MessagePostProcessor postProcessor;
+	private @Nullable MessagePostProcessor postProcessor;
 
 	/**
 	 * Sets the encoding used to read from and write to {@link TextMessage} messages.

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/JmsMessageSender.java

@@ -27,11 +27,13 @@ import jakarta.jms.Message;
 import jakarta.jms.Queue;
 import jakarta.jms.Session;
 import jakarta.jms.Topic;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.jms.connection.ConnectionFactoryUtils;
 import org.springframework.jms.core.MessagePostProcessor;
 import org.springframework.jms.support.JmsUtils;
 import org.springframework.jms.support.destination.JmsDestinationAccessor;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 import org.springframework.ws.transport.WebServiceConnection;
 import org.springframework.ws.transport.WebServiceMessageSender;
@@ -117,7 +119,7 @@ public class JmsMessageSender extends JmsDestinationAccessor implements WebServi
 
 	private String textMessageEncoding = DEFAULT_TEXT_MESSAGE_ENCODING;
 
-	private MessagePostProcessor postProcessor;
+	private @Nullable MessagePostProcessor postProcessor;
 
 	/**
 	 * Create a new {@code JmsMessageSender}
@@ -165,6 +167,8 @@ public class JmsMessageSender extends JmsDestinationAccessor implements WebServi
 
 	@Override
 	public WebServiceConnection createConnection(URI uri) throws IOException {
+		ConnectionFactory connectionFactory = getConnectionFactory();
+		Assert.notNull(connectionFactory, "ConnectionFactory is required");
 		Connection jmsConnection = null;
 		Session jmsSession = null;
 		try {
@@ -172,8 +176,8 @@ public class JmsMessageSender extends JmsDestinationAccessor implements WebServi
 			jmsSession = createSession(jmsConnection);
 			Destination requestDestination = resolveRequestDestination(jmsSession, uri);
 			Message requestMessage = createRequestMessage(jmsSession, uri);
-			JmsSenderConnection wsConnection = new JmsSenderConnection(getConnectionFactory(), jmsConnection,
-					jmsSession, requestDestination, requestMessage);
+			JmsSenderConnection wsConnection = new JmsSenderConnection(connectionFactory, jmsConnection, jmsSession,
+					requestDestination, requestMessage);
 			wsConnection.setDeliveryMode(JmsTransportUtils.getDeliveryMode(uri));
 			wsConnection.setPriority(JmsTransportUtils.getPriority(uri));
 			wsConnection.setReceiveTimeout(this.receiveTimeout);
@@ -197,10 +201,12 @@ public class JmsMessageSender extends JmsDestinationAccessor implements WebServi
 	}
 
 	private Destination resolveRequestDestination(Session session, URI uri) throws JMSException {
-		return resolveDestinationName(session, JmsTransportUtils.getDestinationName(uri));
+		String destinationName = JmsTransportUtils.getDestinationName(uri);
+		Assert.notNull(destinationName, "No destination name found for URI [" + uri + "]");
+		return resolveDestinationName(session, destinationName);
 	}
 
-	private Destination resolveResponseDestination(Session session, URI uri) throws JMSException {
+	private @Nullable Destination resolveResponseDestination(Session session, URI uri) throws JMSException {
 		String destinationName = JmsTransportUtils.getReplyToName(uri);
 		return StringUtils.hasLength(destinationName) ? resolveDestinationName(session, destinationName) : null;
 	}

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/JmsReceiverConnection.java

@@ -29,6 +29,7 @@ import jakarta.jms.Message;
 import jakarta.jms.MessageProducer;
 import jakarta.jms.Session;
 import jakarta.jms.TextMessage;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.jms.core.MessagePostProcessor;
 import org.springframework.jms.support.JmsUtils;
@@ -57,11 +58,11 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 
 	private final Session session;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
-	private String textMessageEncoding;
+	private @Nullable String textMessageEncoding;
 
-	private MessagePostProcessor postProcessor;
+	private @Nullable MessagePostProcessor postProcessor;
 
 	private JmsReceiverConnection(Message requestMessage, Session session) {
 		Assert.notNull(requestMessage, "requestMessage must not be null");
@@ -89,7 +90,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 		this.textMessageEncoding = encoding;
 	}
 
-	void setPostProcessor(MessagePostProcessor postProcessor) {
+	void setPostProcessor(@Nullable MessagePostProcessor postProcessor) {
 		this.postProcessor = postProcessor;
 	}
 
@@ -105,7 +106,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 	 * Returns the response message, if any, for this connection. Returns either a
 	 * {@link BytesMessage} or a {@link TextMessage}.
 	 */
-	public Message getResponseMessage() {
+	public @Nullable Message getResponseMessage() {
 		return this.responseMessage;
 	}
 
@@ -114,7 +115,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 	 */
 
 	@Override
-	public URI getUri() throws URISyntaxException {
+	public @Nullable URI getUri() throws URISyntaxException {
 		try {
 			return JmsTransportUtils.toUri(this.requestMessage.getJMSDestination());
 		}
@@ -128,7 +129,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 	 */
 
 	@Override
-	public String getErrorMessage() throws IOException {
+	public @Nullable String getErrorMessage() throws IOException {
 		return null;
 	}
 
@@ -167,6 +168,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 			return new BytesMessageInputStream((BytesMessage) this.requestMessage);
 		}
 		else if (this.requestMessage instanceof TextMessage) {
+			Assert.notNull(this.textMessageEncoding, "MessageEncoding for TextMessage is required");
 			return new TextMessageInputStream((TextMessage) this.requestMessage, this.textMessageEncoding);
 		}
 		else {
@@ -181,15 +183,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 	@Override
 	protected void onSendBeforeWrite(WebServiceMessage message) throws IOException {
 		try {
-			if (this.requestMessage instanceof BytesMessage) {
-				this.responseMessage = this.session.createBytesMessage();
-			}
-			else if (this.requestMessage instanceof TextMessage) {
-				this.responseMessage = this.session.createTextMessage();
-			}
-			else {
-				throw new IllegalStateException("Unknown request message type [" + this.requestMessage + "]");
-			}
+			this.responseMessage = createResponseMessage();
 			String correlation = this.requestMessage.getJMSCorrelationID();
 			if (correlation == null) {
 				correlation = this.requestMessage.getJMSMessageID();
@@ -201,8 +195,21 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 		}
 	}
 
+	private Message createResponseMessage() throws JMSException {
+		if (this.requestMessage instanceof BytesMessage) {
+			return this.session.createBytesMessage();
+		}
+		else if (this.requestMessage instanceof TextMessage) {
+			return this.session.createTextMessage();
+		}
+		else {
+			throw new IllegalStateException("Unknown request message type [" + this.requestMessage + "]");
+		}
+	}
+
 	@Override
 	public void addResponseHeader(String name, String value) throws IOException {
+		Assert.state(this.responseMessage != null, "Response message is not available");
 		try {
 			JmsTransportUtils.addHeader(this.responseMessage, name, value);
 		}
@@ -217,6 +224,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 			return new BytesMessageOutputStream((BytesMessage) this.responseMessage);
 		}
 		else if (this.responseMessage instanceof TextMessage) {
+			Assert.notNull(this.textMessageEncoding, "MessageEncoding for TextMessage is required");
 			return new TextMessageOutputStream((TextMessage) this.responseMessage, this.textMessageEncoding);
 		}
 		else {
@@ -226,6 +234,7 @@ public class JmsReceiverConnection extends AbstractReceiverConnection {
 
 	@Override
 	protected void onSendAfterWrite(WebServiceMessage message) throws IOException {
+		Assert.state(this.responseMessage != null, "Response message is not available");
 		MessageProducer messageProducer = null;
 		try {
 			if (this.requestMessage.getJMSReplyTo() != null) {

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/JmsSenderConnection.java

@@ -34,6 +34,7 @@ import jakarta.jms.MessageProducer;
 import jakarta.jms.Session;
 import jakarta.jms.TemporaryQueue;
 import jakarta.jms.TextMessage;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.jms.connection.ConnectionFactoryUtils;
 import org.springframework.jms.core.MessagePostProcessor;
@@ -64,9 +65,9 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 
 	private Message requestMessage;
 
-	private Destination responseDestination;
+	private @Nullable Destination responseDestination;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
 	private long receiveTimeout;
 
@@ -76,9 +77,9 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 
 	private int priority;
 
-	private String textMessageEncoding;
+	private @Nullable String textMessageEncoding;
 
-	private MessagePostProcessor postProcessor;
+	private @Nullable MessagePostProcessor postProcessor;
 
 	private boolean sessionTransacted = false;
 
@@ -111,7 +112,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	 * Returns the response message, if any, for this connection. Returns either a
 	 * {@link BytesMessage} or a {@link TextMessage}.
 	 */
-	public Message getResponseMessage() {
+	public @Nullable Message getResponseMessage() {
 		return this.responseMessage;
 	}
 
@@ -119,7 +120,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	 * Package-friendly setters
 	 */
 
-	void setResponseDestination(Destination responseDestination) {
+	void setResponseDestination(@Nullable Destination responseDestination) {
 		this.responseDestination = responseDestination;
 	}
 
@@ -143,7 +144,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 		this.textMessageEncoding = textMessageEncoding;
 	}
 
-	void setPostProcessor(MessagePostProcessor postProcessor) {
+	void setPostProcessor(@Nullable MessagePostProcessor postProcessor) {
 		this.postProcessor = postProcessor;
 	}
 
@@ -156,7 +157,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	 */
 
 	@Override
-	public URI getUri() throws URISyntaxException {
+	public @Nullable URI getUri() throws URISyntaxException {
 		try {
 			return JmsTransportUtils.toUri(this.requestDestination);
 		}
@@ -175,7 +176,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	}
 
 	@Override
-	public String getErrorMessage() throws IOException {
+	public @Nullable String getErrorMessage() throws IOException {
 		return null;
 	}
 
@@ -199,6 +200,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 			return new BytesMessageOutputStream((BytesMessage) this.requestMessage);
 		}
 		else if (this.requestMessage instanceof TextMessage) {
+			Assert.notNull(this.textMessageEncoding, "MessageEncoding for TextMessage is required");
 			return new TextMessageOutputStream((TextMessage) this.requestMessage, this.textMessageEncoding);
 		}
 		else {
@@ -277,9 +279,10 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 		}
 		finally {
 			JmsUtils.closeMessageConsumer(messageConsumer);
-			if (this.temporaryResponseQueueCreated) {
+			if (this.temporaryResponseQueueCreated
+					&& this.responseDestination instanceof TemporaryQueue temporaryQueue) {
 				try {
-					((TemporaryQueue) this.responseDestination).delete();
+					temporaryQueue.delete();
 				}
 				catch (JMSException ex) {
 					// ignore
@@ -296,6 +299,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	@Override
 	public Iterator<String> getResponseHeaderNames() throws IOException {
 		try {
+			Assert.state(this.responseMessage != null, "ResponseMessage is required");
 			return JmsTransportUtils.getHeaderNames(this.responseMessage);
 		}
 		catch (JMSException ex) {
@@ -306,6 +310,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 	@Override
 	public Iterator<String> getResponseHeaders(String name) throws IOException {
 		try {
+			Assert.state(this.responseMessage != null, "ResponseMessage is required");
 			return JmsTransportUtils.getHeaders(this.responseMessage, name);
 		}
 		catch (JMSException ex) {
@@ -319,6 +324,7 @@ public class JmsSenderConnection extends AbstractSenderConnection {
 			return new BytesMessageInputStream((BytesMessage) this.responseMessage);
 		}
 		else if (this.responseMessage instanceof TextMessage) {
+			Assert.notNull(this.textMessageEncoding, "MessageEncoding for TextMessage is required");
 			return new TextMessageInputStream((TextMessage) this.responseMessage, this.textMessageEncoding);
 		}
 		else {

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Package providing support for handling messages via JMS.
  */
+@NullMarked
 package org.springframework.ws.transport.jms;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/support/JmsTransportUtils.java

@@ -32,6 +32,7 @@ import jakarta.jms.JMSException;
 import jakarta.jms.Message;
 import jakarta.jms.Queue;
 import jakarta.jms.Topic;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.ws.transport.jms.JmsTransportConstants;
 
@@ -100,7 +101,7 @@ public abstract class JmsTransportUtils {
 	 * @param destination the destination
 	 * @return a jms URI
 	 */
-	public static URI toUri(Destination destination) throws URISyntaxException, JMSException {
+	public static @Nullable URI toUri(@Nullable Destination destination) throws URISyntaxException, JMSException {
 		if (destination == null) {
 			return null;
 		}
@@ -118,7 +119,7 @@ public abstract class JmsTransportUtils {
 	}
 
 	/** Returns the destination name of the given URI. */
-	public static String getDestinationName(URI uri) {
+	public static @Nullable String getDestinationName(URI uri) {
 		return getStringParameter(DESTINATION_NAME_PATTERN, uri);
 	}
 
@@ -215,11 +216,11 @@ public abstract class JmsTransportUtils {
 	 * Returns the reply-to name of the given URI.
 	 * @see Message#setJMSReplyTo(Destination)
 	 */
-	public static String getReplyToName(URI uri) {
+	public static @Nullable String getReplyToName(URI uri) {
 		return getStringParameter(REPLY_TO_NAME_PATTERN, uri);
 	}
 
-	private static String getStringParameter(Pattern pattern, URI uri) {
+	private static @Nullable String getStringParameter(Pattern pattern, URI uri) {
 		Matcher matcher = pattern.matcher(uri.getSchemeSpecificPart());
 		if (matcher.find() && matcher.groupCount() == 1) {
 			return matcher.group(1);

spring-ws-support/src/main/java/org/springframework/ws/transport/jms/support/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Classes supporting the org.springframework.ws.transport.jms package.
  */
+@NullMarked
 package org.springframework.ws.transport.jms.support;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/MailMessageReceiver.java

@@ -16,6 +16,7 @@
 
 package org.springframework.ws.transport.mail;
 
+import java.util.Objects;
 import java.util.Properties;
 
 import jakarta.mail.Folder;
@@ -27,6 +28,7 @@ import jakarta.mail.Store;
 import jakarta.mail.URLName;
 import jakarta.mail.internet.AddressException;
 import jakarta.mail.internet.InternetAddress;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.scheduling.SchedulingAwareRunnable;
 import org.springframework.util.Assert;
@@ -58,18 +60,21 @@ public class MailMessageReceiver extends AbstractAsyncStandaloneMessageReceiver
 
 	private Session session = Session.getInstance(new Properties(), null);
 
+	@SuppressWarnings("NullAway.Init")
 	private URLName storeUri;
 
+	@SuppressWarnings("NullAway.Init")
 	private URLName transportUri;
 
-	private Folder folder;
-
-	private Store store;
-
-	private InternetAddress from;
-
+	@SuppressWarnings("NullAway.Init")
 	private MonitoringStrategy monitoringStrategy;
 
+	private @Nullable Folder folder;
+
+	private @Nullable Store store;
+
+	private @Nullable InternetAddress from;
+
 	/** Sets the from address to use when sending response messages. */
 	public void setFrom(String from) throws AddressException {
 		this.from = new InternetAddress(from);
@@ -201,7 +206,7 @@ public class MailMessageReceiver extends AbstractAsyncStandaloneMessageReceiver
 		if (this.folder != null && this.folder.isOpen()) {
 			return;
 		}
-		this.folder = this.store.getFolder(this.storeUri);
+		this.folder = Objects.requireNonNull(this.store).getFolder(this.storeUri);
 		if (this.folder == null || !this.folder.exists()) {
 			throw new IllegalStateException("No default folder to receive from");
 		}
@@ -228,7 +233,7 @@ public class MailMessageReceiver extends AbstractAsyncStandaloneMessageReceiver
 				while (isRunning()) {
 					try {
 						Message[] messages = MailMessageReceiver.this.monitoringStrategy
-							.monitor(MailMessageReceiver.this.folder);
+							.monitor(Objects.requireNonNull(MailMessageReceiver.this.folder));
 						for (Message message : messages) {
 							MessageHandler handler = new MessageHandler(message);
 							execute(handler);
@@ -274,7 +279,7 @@ public class MailMessageReceiver extends AbstractAsyncStandaloneMessageReceiver
 			MailReceiverConnection connection = new MailReceiverConnection(this.message,
 					MailMessageReceiver.this.session);
 			connection.setTransportUri(MailMessageReceiver.this.transportUri);
-			connection.setFrom(MailMessageReceiver.this.from);
+			connection.setFrom(Objects.requireNonNull(MailMessageReceiver.this.from));
 			try {
 				handleConnection(connection);
 			}

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/MailMessageSender.java

@@ -25,6 +25,7 @@ import jakarta.mail.URLName;
 import jakarta.mail.internet.AddressException;
 import jakarta.mail.internet.InternetAddress;
 import jakarta.mail.internet.MimeMessage;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.Assert;
@@ -83,11 +84,11 @@ public class MailMessageSender implements WebServiceMessageSender, InitializingB
 
 	private Session session = Session.getInstance(new Properties(), null);
 
-	private URLName storeUri;
+	private @Nullable URLName storeUri;
 
-	private URLName transportUri;
+	private @Nullable URLName transportUri;
 
-	private InternetAddress from;
+	private @Nullable InternetAddress from;
 
 	/**
 	 * Sets the from address to use when sending request messages.
@@ -163,7 +164,10 @@ public class MailMessageSender implements WebServiceMessageSender, InitializingB
 
 	@Override
 	public WebServiceConnection createConnection(URI uri) throws IOException {
+		Assert.notNull(this.transportUri, "'transportUri' is required");
+		Assert.notNull(this.storeUri, "'storeUri' is required");
 		InternetAddress to = MailTransportUtils.getTo(uri);
+		Assert.notNull(to, "No TO address found for '" + uri + "'");
 		MailSenderConnection connection = new MailSenderConnection(this.session, this.transportUri, this.storeUri, to,
 				this.receiveSleepTime);
 		if (this.from != null) {

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/MailReceiverConnection.java

@@ -39,6 +39,7 @@ import jakarta.mail.Session;
 import jakarta.mail.Transport;
 import jakarta.mail.URLName;
 import jakarta.mail.internet.InternetAddress;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -62,15 +63,15 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 
 	private final Session session;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
-	private ByteArrayOutputStream responseBuffer;
+	private @Nullable ByteArrayOutputStream responseBuffer;
 
-	private String responseContentType;
+	private @Nullable String responseContentType;
 
-	private URLName transportUri;
+	private @Nullable URLName transportUri;
 
-	private InternetAddress from;
+	private @Nullable InternetAddress from;
 
 	/** Constructs a new Mail connection with the given parameters. */
 	protected MailReceiverConnection(Message requestMessage, Session session) {
@@ -87,6 +88,7 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 
 	/** Returns the response message, if any, for this connection. */
 	public Message getResponseMessage() {
+		Assert.notNull(this.responseMessage, "ResponseMessage is not available");
 		return this.responseMessage;
 	}
 
@@ -125,7 +127,7 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 	 */
 
 	@Override
-	public String getErrorMessage() throws IOException {
+	public @Nullable String getErrorMessage() throws IOException {
 		return null;
 	}
 
@@ -178,7 +180,7 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 	@Override
 	public void addResponseHeader(String name, String value) throws IOException {
 		try {
-			this.responseMessage.addHeader(name, value);
+			getResponseMessage().addHeader(name, value);
 			if (TransportConstants.HEADER_CONTENT_TYPE.equals(name)) {
 				this.responseContentType = value;
 			}
@@ -190,6 +192,7 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 
 	@Override
 	protected OutputStream getResponseOutputStream() throws IOException {
+		Assert.state(this.responseBuffer != null, "onSendBeforeWrite has not been called");
 		return this.responseBuffer;
 	}
 
@@ -213,9 +216,12 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 	@Override
 	protected void onSendAfterWrite(WebServiceMessage message) throws IOException {
 		Transport transport = null;
+		Assert.state(this.responseMessage != null, "onSendAfterWrite has not been called");
+		Assert.state(this.responseBuffer != null, "onSendAfterWrite has not been called");
+		Assert.notNull(this.transportUri, "'transportUri' must not be null");
 		try {
 			this.responseMessage.setDataHandler(new DataHandler(
-					new ByteArrayDataSource(this.responseContentType, this.responseBuffer.toByteArray())));
+					new ByteArrayDataSource(this.responseBuffer.toByteArray(), this.responseContentType)));
 			transport = this.session.getTransport(this.transportUri);
 			transport.connect();
 			this.responseMessage.saveChanges();
@@ -235,9 +241,9 @@ public class MailReceiverConnection extends AbstractReceiverConnection {
 
 		private final byte[] data;
 
-		ByteArrayDataSource(String contentType, byte[] data) {
+		ByteArrayDataSource(byte[] data, @Nullable String contentType) {
 			this.data = data;
-			this.contentType = contentType;
+			this.contentType = (contentType != null) ? contentType : "application/octet-stream";
 		}
 
 		@Override

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/MailSenderConnection.java

@@ -47,6 +47,7 @@ import jakarta.mail.search.HeaderTerm;
 import jakarta.mail.search.SearchTerm;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 import org.springframework.ws.WebServiceMessage;
@@ -70,11 +71,11 @@ public class MailSenderConnection extends AbstractSenderConnection {
 
 	private final Session session;
 
-	private MimeMessage requestMessage;
+	private @Nullable MimeMessage requestMessage;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
-	private String requestContentType;
+	private @Nullable String requestContentType;
 
 	private boolean deleteAfterReceive = false;
 
@@ -82,19 +83,19 @@ public class MailSenderConnection extends AbstractSenderConnection {
 
 	private final URLName transportUri;
 
-	private ByteArrayOutputStream requestBuffer;
+	private @Nullable ByteArrayOutputStream requestBuffer;
 
-	private InternetAddress from;
+	private @Nullable InternetAddress from;
 
 	private final InternetAddress to;
 
-	private String subject;
+	private @Nullable String subject;
 
 	private final long receiveTimeout;
 
-	private Store store;
+	private @Nullable Store store;
 
-	private Folder folder;
+	private @Nullable Folder folder;
 
 	/** Constructs a new Mail connection with the given parameters. */
 	protected MailSenderConnection(Session session, URLName transportUri, URLName storeUri, InternetAddress to,
@@ -111,12 +112,14 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	}
 
 	/** Returns the request message for this connection. */
-	public Message getRequestMessage() {
+	public MimeMessage getRequestMessage() {
+		Assert.notNull(this.requestMessage, "RequestMessage is not available");
 		return this.requestMessage;
 	}
 
 	/** Returns the response message, if any, for this connection. */
 	public Message getResponseMessage() {
+		Assert.notNull(this.responseMessage, "ResponseMessage is not available");
 		return this.responseMessage;
 	}
 
@@ -165,7 +168,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	@Override
 	public void addRequestHeader(String name, String value) throws IOException {
 		try {
-			this.requestMessage.addHeader(name, value);
+			getRequestMessage().addHeader(name, value);
 			if (TransportConstants.HEADER_CONTENT_TYPE.equals(name)) {
 				this.requestContentType = value;
 			}
@@ -177,15 +180,18 @@ public class MailSenderConnection extends AbstractSenderConnection {
 
 	@Override
 	protected OutputStream getRequestOutputStream() throws IOException {
+		Assert.notNull(this.requestBuffer, "Request OutputStream is not available");
 		return this.requestBuffer;
 	}
 
 	@Override
 	protected void onSendAfterWrite(WebServiceMessage message) throws IOException {
+		Assert.state(this.requestMessage != null, "onSendBeforeWrite has not been called");
+		Assert.state(this.requestBuffer != null, "onSendBeforeWrite has not been called");
 		Transport transport = null;
 		try {
 			this.requestMessage.setDataHandler(new DataHandler(
-					new ByteArrayDataSource(this.requestContentType, this.requestBuffer.toByteArray())));
+					new ByteArrayDataSource(this.requestBuffer.toByteArray(), this.requestContentType)));
 			transport = this.session.getTransport(this.transportUri);
 			transport.connect();
 			this.requestMessage.saveChanges();
@@ -195,7 +201,9 @@ public class MailSenderConnection extends AbstractSenderConnection {
 			throw new MailTransportException(ex);
 		}
 		finally {
-			MailTransportUtils.closeService(transport);
+			if (transport != null) {
+				MailTransportUtils.closeService(transport);
+			}
 		}
 	}
 
@@ -205,6 +213,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 
 	@Override
 	protected void onReceiveBeforeRead() throws IOException {
+		Assert.state(this.requestMessage != null, "onSendBeforeWrite has not been called");
 		try {
 			String requestMessageId = this.requestMessage.getMessageID();
 			Assert.hasLength(requestMessageId, "No Message-ID found on request message [" + this.requestMessage + "]");
@@ -215,7 +224,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 				// Re-interrupt current thread, to allow other threads to react.
 				Thread.currentThread().interrupt();
 			}
-			openFolder();
+			this.folder = openFolder();
 			SearchTerm searchTerm = new HeaderTerm(MailTransportConstants.HEADER_IN_REPLY_TO, requestMessageId);
 			Message[] responses = this.folder.search(searchTerm);
 			if (responses.length > 0) {
@@ -224,7 +233,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 				}
 				this.responseMessage = responses[0];
 			}
-			if (this.deleteAfterReceive) {
+			if (this.deleteAfterReceive && this.responseMessage != null) {
 				this.responseMessage.setFlag(Flags.Flag.DELETED, true);
 			}
 		}
@@ -233,19 +242,20 @@ public class MailSenderConnection extends AbstractSenderConnection {
 		}
 	}
 
-	private void openFolder() throws MessagingException {
+	private Folder openFolder() throws MessagingException {
 		this.store = this.session.getStore(this.storeUri);
 		this.store.connect();
-		this.folder = this.store.getFolder(this.storeUri);
-		if (this.folder == null || !this.folder.exists()) {
+		Folder folder = this.store.getFolder(this.storeUri);
+		if (folder == null || !folder.exists()) {
 			throw new IllegalStateException("No default folder to receive from");
 		}
 		if (this.deleteAfterReceive) {
-			this.folder.open(Folder.READ_WRITE);
+			folder.open(Folder.READ_WRITE);
 		}
 		else {
-			this.folder.open(Folder.READ_ONLY);
+			folder.open(Folder.READ_ONLY);
 		}
+		return folder;
 	}
 
 	@Override
@@ -257,7 +267,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	public Iterator<String> getResponseHeaderNames() throws IOException {
 		try {
 			List<String> headers = new ArrayList<>();
-			Enumeration<?> enumeration = this.responseMessage.getAllHeaders();
+			Enumeration<?> enumeration = getResponseMessage().getAllHeaders();
 			while (enumeration.hasMoreElements()) {
 				Header header = (Header) enumeration.nextElement();
 				headers.add(header.getName());
@@ -272,7 +282,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	@Override
 	public Iterator<String> getResponseHeaders(String name) throws IOException {
 		try {
-			String[] headers = this.responseMessage.getHeader(name);
+			String[] headers = getResponseMessage().getHeader(name);
 			return Arrays.asList(headers).iterator();
 		}
 		catch (MessagingException ex) {
@@ -284,7 +294,7 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	@Override
 	protected InputStream getResponseInputStream() throws IOException {
 		try {
-			return this.responseMessage.getDataHandler().getInputStream();
+			return getResponseMessage().getDataHandler().getInputStream();
 		}
 		catch (MessagingException ex) {
 			throw new MailTransportException(ex);
@@ -297,14 +307,18 @@ public class MailSenderConnection extends AbstractSenderConnection {
 	}
 
 	@Override
-	public String getErrorMessage() throws IOException {
+	public @Nullable String getErrorMessage() throws IOException {
 		return null;
 	}
 
 	@Override
 	public void onClose() throws IOException {
-		MailTransportUtils.closeFolder(this.folder, this.deleteAfterReceive);
-		MailTransportUtils.closeService(this.store);
+		if (this.folder != null) {
+			MailTransportUtils.closeFolder(this.folder, this.deleteAfterReceive);
+		}
+		if (this.store != null) {
+			MailTransportUtils.closeService(this.store);
+		}
 	}
 
 	private static final class ByteArrayDataSource implements DataSource {
@@ -313,9 +327,9 @@ public class MailSenderConnection extends AbstractSenderConnection {
 
 		private final byte[] data;
 
-		ByteArrayDataSource(String contentType, byte[] data) {
+		ByteArrayDataSource(byte[] data, @Nullable String contentType) {
 			this.data = data;
-			this.contentType = contentType;
+			this.contentType = (contentType != null) ? contentType : "application/octet-stream";
 		}
 
 		@Override

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/monitor/ImapIdleMonitoringStrategy.java

@@ -23,6 +23,7 @@ import jakarta.mail.event.MessageCountAdapter;
 import jakarta.mail.event.MessageCountEvent;
 import jakarta.mail.event.MessageCountListener;
 import org.eclipse.angus.mail.imap.IMAPFolder;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 
@@ -38,7 +39,7 @@ import org.springframework.util.Assert;
  */
 public class ImapIdleMonitoringStrategy extends AbstractMonitoringStrategy {
 
-	private MessageCountListener messageCountListener;
+	private @Nullable MessageCountListener messageCountListener;
 
 	@Override
 	protected void waitForNewMessages(Folder folder) throws MessagingException, InterruptedException {

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/monitor/package-info.java

@@ -18,4 +18,7 @@
  * Provides the MonitoringStrategy interface and implementations. Used for monitoring a
  * JavaMail Folder for new email messages.
  */
+@NullMarked
 package org.springframework.ws.transport.mail.monitor;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Package providing support for handling messages via email.
  */
+@NullMarked
 package org.springframework.ws.transport.mail;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/support/MailTransportUtils.java

@@ -29,6 +29,7 @@ import jakarta.mail.internet.AddressException;
 import jakarta.mail.internet.InternetAddress;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.StringUtils;
 import org.springframework.ws.transport.mail.MailTransportConstants;
@@ -50,7 +51,7 @@ public abstract class MailTransportUtils {
 	private MailTransportUtils() {
 	}
 
-	public static InternetAddress getTo(URI uri) {
+	public static @Nullable InternetAddress getTo(URI uri) {
 		Matcher matcher = TO_PATTERN.matcher(uri.getSchemeSpecificPart());
 		if (matcher.find()) {
 			for (int i = 1; i <= matcher.groupCount(); i++) {
@@ -68,7 +69,7 @@ public abstract class MailTransportUtils {
 		return null;
 	}
 
-	public static String getSubject(URI uri) {
+	public static @Nullable String getSubject(URI uri) {
 		Matcher matcher = SUBJECT_PATTERN.matcher(uri.getSchemeSpecificPart());
 		if (matcher.find()) {
 			return matcher.group(1);
@@ -83,7 +84,7 @@ public abstract class MailTransportUtils {
 	 * @see jakarta.mail.Transport
 	 * @see jakarta.mail.Store
 	 */
-	public static void closeService(Service service) {
+	public static void closeService(@Nullable Service service) {
 		if (service != null) {
 			try {
 				service.close();
@@ -110,7 +111,7 @@ public abstract class MailTransportUtils {
 	 * @param folder the JavaMail Folder to close (may be {@code null})
 	 * @param expunge whether all deleted messages should be expunged from the folder
 	 */
-	public static void closeFolder(Folder folder, boolean expunge) {
+	public static void closeFolder(@Nullable Folder folder, boolean expunge) {
 		if (folder != null && folder.isOpen()) {
 			try {
 				folder.close(expunge);
@@ -172,7 +173,7 @@ public abstract class MailTransportUtils {
 	 * @param subject the subject, may be {@code null}
 	 * @return a mailto URI
 	 */
-	public static URI toUri(InternetAddress to, String subject) throws URISyntaxException {
+	public static URI toUri(InternetAddress to, @Nullable String subject) throws URISyntaxException {
 		if (StringUtils.hasLength(subject)) {
 			return new URI(MailTransportConstants.MAIL_URI_SCHEME, to.getAddress() + "?subject=" + subject, null);
 		}

spring-ws-support/src/main/java/org/springframework/ws/transport/mail/support/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Classes supporting the org.springframework.ws.transport.mail package.
  */
+@NullMarked
 package org.springframework.ws.transport.mail.support;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/XmppMessageReceiver.java

@@ -26,7 +26,9 @@ import org.jivesoftware.smack.filter.StanzaTypeFilter;
 import org.jivesoftware.smack.packet.Message;
 import org.jivesoftware.smack.packet.Stanza;
 import org.jivesoftware.smack.tcp.XMPPTCPConnection;
+import org.jspecify.annotations.Nullable;
 
+import org.springframework.util.Assert;
 import org.springframework.ws.transport.support.AbstractStandaloneMessageReceiver;
 
 /**
@@ -51,9 +53,9 @@ public class XmppMessageReceiver extends AbstractStandaloneMessageReceiver {
 	 */
 	public static final String DEFAULT_MESSAGE_ENCODING = "UTF-8";
 
-	private XMPPTCPConnection connection;
+	private @Nullable XMPPTCPConnection connection;
 
-	private WebServicePacketListener packetListener;
+	private @Nullable WebServicePacketListener packetListener;
 
 	private final String messageEncoding = DEFAULT_MESSAGE_ENCODING;
 
@@ -65,11 +67,16 @@ public class XmppMessageReceiver extends AbstractStandaloneMessageReceiver {
 		this.connection = connection;
 	}
 
+	private XMPPTCPConnection getConnection() {
+		Assert.state(this.connection != null, "Connection is required");
+		return this.connection;
+	}
+
 	@Override
 	protected void onActivate() throws XMPPException, IOException, SmackException {
-		if (!this.connection.isConnected()) {
+		if (!getConnection().isConnected()) {
 			try {
-				this.connection.connect();
+				getConnection().connect();
 			}
 			catch (InterruptedException ex) {
 				throw new IOException(ex);
@@ -80,29 +87,29 @@ public class XmppMessageReceiver extends AbstractStandaloneMessageReceiver {
 	@Override
 	protected void onStart() {
 		if (this.logger.isInfoEnabled()) {
-			this.logger.info("Starting XMPP receiver [" + this.connection.getUser() + "]");
+			this.logger.info("Starting XMPP receiver [" + getConnection().getUser() + "]");
 		}
 		this.packetListener = new WebServicePacketListener();
 		StanzaFilter packetFilter = new StanzaTypeFilter(Message.class);
-		this.connection.addAsyncStanzaListener(this.packetListener, packetFilter);
+		getConnection().addAsyncStanzaListener(this.packetListener, packetFilter);
 	}
 
 	@Override
 	protected void onStop() {
 		if (this.logger.isInfoEnabled()) {
-			this.logger.info("Stopping XMPP receiver [" + this.connection.getUser() + "]");
+			this.logger.info("Stopping XMPP receiver [" + getConnection().getUser() + "]");
 		}
-		this.connection.removeAsyncStanzaListener(this.packetListener);
+		getConnection().removeAsyncStanzaListener(this.packetListener);
 		this.packetListener = null;
 	}
 
 	@Override
 	protected void onShutdown() {
 		if (this.logger.isInfoEnabled()) {
-			this.logger.info("Shutting down XMPP receiver [" + this.connection.getUser() + "]");
+			this.logger.info("Shutting down XMPP receiver [" + getConnection().getUser() + "]");
 		}
-		if (this.connection.isConnected()) {
-			this.connection.disconnect();
+		if (getConnection().isConnected()) {
+			getConnection().disconnect();
 		}
 	}
 
@@ -113,8 +120,7 @@ public class XmppMessageReceiver extends AbstractStandaloneMessageReceiver {
 			XmppMessageReceiver.this.logger.info("Received " + packet);
 			if (packet instanceof Message message) {
 				try {
-					XmppReceiverConnection wsConnection = new XmppReceiverConnection(
-							XmppMessageReceiver.this.connection, message);
+					XmppReceiverConnection wsConnection = new XmppReceiverConnection(getConnection(), message);
 					wsConnection.setMessageEncoding(XmppMessageReceiver.this.messageEncoding);
 					handleConnection(wsConnection);
 				}

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/XmppMessageSender.java

@@ -18,9 +18,11 @@ package org.springframework.ws.transport.xmpp;
 
 import java.io.IOException;
 import java.net.URI;
+import java.util.Objects;
 import java.util.UUID;
 
 import org.jivesoftware.smack.XMPPConnection;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.Assert;
@@ -58,7 +60,7 @@ public class XmppMessageSender implements WebServiceMessageSender, InitializingB
 
 	private String messageEncoding = DEFAULT_MESSAGE_ENCODING;
 
-	private XMPPConnection connection;
+	private @Nullable XMPPConnection connection;
 
 	/**
 	 * Sets the {@code XMPPConnection}. Setting this property is required.
@@ -93,7 +95,7 @@ public class XmppMessageSender implements WebServiceMessageSender, InitializingB
 	public WebServiceConnection createConnection(URI uri) throws IOException {
 		String to = XmppTransportUtils.getTo(uri);
 		String thread = createThread();
-		XmppSenderConnection connection = new XmppSenderConnection(this.connection, to, thread);
+		XmppSenderConnection connection = new XmppSenderConnection(Objects.requireNonNull(this.connection), to, thread);
 		connection.setReceiveTimeout(this.receiveTimeout);
 		connection.setMessageEncoding(this.messageEncoding);
 		return connection;

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/XmppReceiverConnection.java

@@ -22,10 +22,12 @@ import java.io.OutputStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Iterator;
+import java.util.Objects;
 
 import org.jivesoftware.smack.SmackException;
 import org.jivesoftware.smack.XMPPConnection;
 import org.jivesoftware.smack.packet.Message;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 import org.springframework.ws.WebServiceMessage;
@@ -48,9 +50,9 @@ public class XmppReceiverConnection extends AbstractReceiverConnection {
 
 	private final Message requestMessage;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
-	private String messageEncoding;
+	private String messageEncoding = XmppMessageReceiver.DEFAULT_MESSAGE_ENCODING;
 
 	public XmppReceiverConnection(XMPPConnection connection, Message requestMessage) {
 		Assert.notNull(connection, "'connection' must not be null");
@@ -65,7 +67,7 @@ public class XmppReceiverConnection extends AbstractReceiverConnection {
 	}
 
 	/** Returns the response message, if any, for this connection. */
-	public Message getResponseMessage() {
+	public @Nullable Message getResponseMessage() {
 		return this.responseMessage;
 	}
 
@@ -96,7 +98,7 @@ public class XmppReceiverConnection extends AbstractReceiverConnection {
 	}
 
 	@Override
-	public String getErrorMessage() {
+	public @Nullable String getErrorMessage() {
 		return XmppTransportUtils.getErrorMessage(this.responseMessage);
 	}
 
@@ -132,12 +134,12 @@ public class XmppReceiverConnection extends AbstractReceiverConnection {
 
 	@Override
 	public void addResponseHeader(String name, String value) throws IOException {
-		XmppTransportUtils.addHeader(this.responseMessage, name, value);
+		XmppTransportUtils.addHeader(Objects.requireNonNull(this.responseMessage), name, value);
 	}
 
 	@Override
 	protected OutputStream getResponseOutputStream() throws IOException {
-		return new MessageOutputStream(this.responseMessage, this.messageEncoding);
+		return new MessageOutputStream(Objects.requireNonNull(this.responseMessage), this.messageEncoding);
 	}
 
 	@Override

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/XmppSenderConnection.java

@@ -22,6 +22,7 @@ import java.io.OutputStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.Iterator;
+import java.util.Objects;
 
 import org.jivesoftware.smack.SmackException;
 import org.jivesoftware.smack.StanzaCollector;
@@ -32,6 +33,7 @@ import org.jivesoftware.smack.filter.StanzaTypeFilter;
 import org.jivesoftware.smack.filter.ThreadFilter;
 import org.jivesoftware.smack.packet.Message;
 import org.jivesoftware.smack.packet.Stanza;
+import org.jspecify.annotations.Nullable;
 import org.jxmpp.jid.impl.JidCreate;
 import org.jxmpp.stringprep.XmppStringprepException;
 
@@ -56,9 +58,9 @@ public class XmppSenderConnection extends AbstractSenderConnection {
 
 	private final XMPPConnection connection;
 
-	private Message responseMessage;
+	private @Nullable Message responseMessage;
 
-	private String messageEncoding;
+	private String messageEncoding = XmppMessageReceiver.DEFAULT_MESSAGE_ENCODING;
 
 	private long receiveTimeout;
 
@@ -82,7 +84,7 @@ public class XmppSenderConnection extends AbstractSenderConnection {
 	}
 
 	/** Returns the response message, if any, for this connection. */
-	public Message getResponseMessage() {
+	public @Nullable Message getResponseMessage() {
 		return this.responseMessage;
 	}
 
@@ -117,7 +119,7 @@ public class XmppSenderConnection extends AbstractSenderConnection {
 	}
 
 	@Override
-	public String getErrorMessage() {
+	public @Nullable String getErrorMessage() {
 		return XmppTransportUtils.getErrorMessage(this.responseMessage);
 	}
 
@@ -185,17 +187,17 @@ public class XmppSenderConnection extends AbstractSenderConnection {
 
 	@Override
 	public Iterator<String> getResponseHeaderNames() {
-		return XmppTransportUtils.getHeaderNames(this.responseMessage);
+		return XmppTransportUtils.getHeaderNames(Objects.requireNonNull(this.responseMessage));
 	}
 
 	@Override
 	public Iterator<String> getResponseHeaders(String name) throws IOException {
-		return XmppTransportUtils.getHeaders(this.responseMessage, name);
+		return XmppTransportUtils.getHeaders(Objects.requireNonNull(this.responseMessage), name);
 	}
 
 	@Override
 	protected InputStream getResponseInputStream() throws IOException {
-		return new MessageInputStream(this.responseMessage, this.messageEncoding);
+		return new MessageInputStream(Objects.requireNonNull(this.responseMessage), this.messageEncoding);
 	}
 
 }

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Package providing support for handling messages via XMPP.
  */
+@NullMarked
 package org.springframework.ws.transport.xmpp;
+
+import org.jspecify.annotations.NullMarked;

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/support/XmppConnectionFactoryBean.java

@@ -17,11 +17,13 @@
 package org.springframework.ws.transport.xmpp.support;
 
 import java.io.IOException;
+import java.util.Objects;
 
 import org.jivesoftware.smack.SmackException;
 import org.jivesoftware.smack.XMPPException;
 import org.jivesoftware.smack.tcp.XMPPTCPConnection;
 import org.jivesoftware.smack.tcp.XMPPTCPConnectionConfiguration;
+import org.jspecify.annotations.Nullable;
 import org.jxmpp.jid.parts.Resourcepart;
 import org.jxmpp.stringprep.XmppStringprepException;
 
@@ -43,19 +45,19 @@ public class XmppConnectionFactoryBean implements FactoryBean<XMPPTCPConnection>
 
 	private static final int DEFAULT_PORT = 5222;
 
-	private XMPPTCPConnection connection;
+	private @Nullable XMPPTCPConnection connection;
 
-	private String host;
+	private @Nullable String host;
 
 	private int port = DEFAULT_PORT;
 
-	private String serviceName;
+	private @Nullable String serviceName;
 
-	private String username;
+	private @Nullable String username;
 
-	private String password;
+	private @Nullable String password;
 
-	private String resource;
+	private @Nullable String resource;
 
 	/** Sets the server host to connect to. */
 	public void setHost(String host) {
@@ -91,6 +93,7 @@ public class XmppConnectionFactoryBean implements FactoryBean<XMPPTCPConnection>
 
 	@Override
 	public void afterPropertiesSet() throws XMPPException, IOException, SmackException {
+		Assert.hasText(this.host, "'host' must not be empty");
 		XMPPTCPConnectionConfiguration configuration = createConnectionConfiguration(this.host, this.port,
 				this.serviceName);
 		Assert.notNull(configuration, "'configuration' must not be null");
@@ -114,12 +117,12 @@ public class XmppConnectionFactoryBean implements FactoryBean<XMPPTCPConnection>
 
 	@Override
 	public void destroy() {
-		this.connection.disconnect();
+		Objects.requireNonNull(this.connection).disconnect();
 	}
 
 	@Override
 	public XMPPTCPConnection getObject() {
-		return this.connection;
+		return Objects.requireNonNull(this.connection);
 	}
 
 	@Override
@@ -138,8 +141,8 @@ public class XmppConnectionFactoryBean implements FactoryBean<XMPPTCPConnection>
 	 * @param port the port to connect to
 	 * @param serviceName the name of the service to connect to. May be {@code null}
 	 */
-	protected XMPPTCPConnectionConfiguration createConnectionConfiguration(String host, int port, String serviceName)
-			throws XmppStringprepException {
+	protected XMPPTCPConnectionConfiguration createConnectionConfiguration(String host, int port,
+			@Nullable String serviceName) throws XmppStringprepException {
 		Assert.hasText(host, "'host' must not be empty");
 		if (StringUtils.hasText(serviceName)) {
 			return XMPPTCPConnectionConfiguration.builder()

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/support/XmppTransportUtils.java

@@ -23,6 +23,7 @@ import java.util.Iterator;
 
 import org.jivesoftware.smack.packet.Message;
 import org.jivesoftware.smackx.jiveproperties.JivePropertiesManager;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.util.Assert;
 import org.springframework.ws.transport.xmpp.XmppTransportConstants;
@@ -49,11 +50,11 @@ public abstract class XmppTransportUtils {
 		return uri.getSchemeSpecificPart();
 	}
 
-	public static boolean hasError(Message message) {
+	public static boolean hasError(@Nullable Message message) {
 		return message != null && Message.Type.error.equals(message.getType());
 	}
 
-	public static String getErrorMessage(Message message) {
+	public static @Nullable String getErrorMessage(@Nullable Message message) {
 		if (message == null || !Message.Type.error.equals(message.getType())) {
 			return null;
 		}

spring-ws-support/src/main/java/org/springframework/ws/transport/xmpp/support/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Support classes for handling messages via XMPP.
  */
+@NullMarked
 package org.springframework.ws.transport.xmpp.support;
+
+import org.jspecify.annotations.NullMarked;