Switch to JSpecify annotations

This commit updates the whole Spring Framework codebase to use JSpecify
annotations instead of Spring null-safety annotations with JSR 305
semantics.

JSpecify provides signficant enhancements such as properly defined
specifications, a canonical dependency with no split-package issue,
better tooling, better Kotlin integration and the capability to specify
generic type, array and varargs element null-safety. Generic type
null-safety is not defined by this commit yet and will be specified
later.

A key difference is that Spring null-safety annotations, following
JSR 305 semantics, apply to fields, parameters and return values,
while JSpecify annotations apply to type usages. That's why this
commit moves nullability annotations closer to the type for fields
and return values.

See gh-28797

spring-websocket/src/main/java/org/springframework/web/socket/AbstractWebSocketMessage.java

@@ -16,7 +16,8 @@
 
 package org.springframework.web.socket;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 

spring-websocket/src/main/java/org/springframework/web/socket/CloseStatus.java

@@ -19,7 +19,8 @@ package org.springframework.web.socket;
 import java.io.Serializable;
 import java.util.Objects;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -152,8 +153,7 @@ public final class CloseStatus implements Serializable {
 
 	private final int code;
 
-	@Nullable
-	private final String reason;
+	private final @Nullable String reason;
 
 
 	/**
@@ -186,8 +186,7 @@ public final class CloseStatus implements Serializable {
 	/**
 	 * Return the reason, or {@code null} if none.
 	 */
-	@Nullable
-	public String getReason() {
+	public @Nullable String getReason() {
 		return this.reason;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/TextMessage.java

@@ -18,7 +18,7 @@ package org.springframework.web.socket;
 
 import java.nio.charset.StandardCharsets;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * A text WebSocket message.
@@ -28,8 +28,7 @@ import org.springframework.lang.Nullable;
  */
 public final class TextMessage extends AbstractWebSocketMessage<String> {
 
-	@Nullable
-	private final byte[] bytes;
+	private final byte @Nullable [] bytes;
 
 
 	/**

spring-websocket/src/main/java/org/springframework/web/socket/WebSocketExtension.java

@@ -22,7 +22,8 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedCaseInsensitiveMap;

spring-websocket/src/main/java/org/springframework/web/socket/WebSocketHttpHeaders.java

@@ -24,8 +24,9 @@ import java.util.Map;
 import java.util.Set;
 import java.util.function.BiConsumer;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 
 /**
@@ -82,8 +83,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Returns the value of the {@code Sec-WebSocket-Accept} header.
 	 * @return the value of the header
 	 */
-	@Nullable
-	public String getSecWebSocketAccept() {
+	public @Nullable String getSecWebSocketAccept() {
 		return getFirst(SEC_WEBSOCKET_ACCEPT);
 	}
 
@@ -129,8 +129,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Returns the value of the {@code Sec-WebSocket-Key} header.
 	 * @return the value of the header
 	 */
-	@Nullable
-	public String getSecWebSocketKey() {
+	public @Nullable String getSecWebSocketKey() {
 		return getFirst(SEC_WEBSOCKET_KEY);
 	}
 
@@ -179,8 +178,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * Returns the value of the {@code Sec-WebSocket-Version} header.
 	 * @return the value of the header
 	 */
-	@Nullable
-	public String getSecWebSocketVersion() {
+	public @Nullable String getSecWebSocketVersion() {
 		return getFirst(SEC_WEBSOCKET_VERSION);
 	}
 
@@ -193,8 +191,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	 * @return the first header value; or {@code null}
 	 */
 	@Override
-	@Nullable
-	public String getFirst(String headerName) {
+	public @Nullable String getFirst(String headerName) {
 		return this.headers.getFirst(headerName);
 	}
 
@@ -257,8 +254,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	}
 
 	@Override
-	@Nullable
-	public List<String> get(Object key) {
+	public @Nullable List<String> get(Object key) {
 		return this.headers.get(key);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/WebSocketSession.java

@@ -24,8 +24,9 @@ import java.security.Principal;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 
 /**
  * A WebSocket session abstraction. Allows sending messages over a WebSocket
@@ -44,8 +45,7 @@ public interface WebSocketSession extends Closeable {
 	/**
 	 * Return the URI used to open the WebSocket connection.
 	 */
-	@Nullable
-	URI getUri();
+	@Nullable URI getUri();
 
 	/**
 	 * Return the headers used in the handshake request (never {@code null}).
@@ -68,28 +68,24 @@ public interface WebSocketSession extends Closeable {
 	 * of the authenticated user.
 	 * <p>If the user has not been authenticated, the method returns <code>null</code>.
 	 */
-	@Nullable
-	Principal getPrincipal();
+	@Nullable Principal getPrincipal();
 
 	/**
 	 * Return the address on which the request was received.
 	 */
-	@Nullable
-	InetSocketAddress getLocalAddress();
+	@Nullable InetSocketAddress getLocalAddress();
 
 	/**
 	 * Return the address of the remote client.
 	 */
-	@Nullable
-	InetSocketAddress getRemoteAddress();
+	@Nullable InetSocketAddress getRemoteAddress();
 
 	/**
 	 * Return the negotiated sub-protocol.
 	 * @return the protocol identifier, or {@code null} if no protocol
 	 * was specified or negotiated successfully
 	 */
-	@Nullable
-	String getAcceptedProtocol();
+	@Nullable String getAcceptedProtocol();
 
 	/**
 	 * Configure the maximum size for an incoming text message.

spring-websocket/src/main/java/org/springframework/web/socket/adapter/AbstractWebSocketSession.java

@@ -22,8 +22,8 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
-import org.springframework.lang.Nullable;
 import org.springframework.util.AlternativeJdkIdGenerator;
 import org.springframework.util.Assert;
 import org.springframework.util.IdGenerator;
@@ -51,8 +51,7 @@ public abstract class AbstractWebSocketSession<T> implements NativeWebSocketSess
 
 	private final Map<String, Object> attributes = new ConcurrentHashMap<>();
 
-	@Nullable
-	private T nativeSession;
+	private @Nullable T nativeSession;
 
 
 	/**
@@ -82,8 +81,7 @@ public abstract class AbstractWebSocketSession<T> implements NativeWebSocketSess
 
 	@SuppressWarnings("unchecked")
 	@Override
-	@Nullable
-	public <R> R getNativeSession(@Nullable Class<R> requiredType) {
+	public <R> @Nullable R getNativeSession(@Nullable Class<R> requiredType) {
 		return (requiredType == null || requiredType.isInstance(this.nativeSession) ? (R) this.nativeSession : null);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/adapter/NativeWebSocketSession.java

@@ -16,7 +16,8 @@
 
 package org.springframework.web.socket.adapter;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.web.socket.WebSocketSession;
 
 /**
@@ -39,7 +40,6 @@ public interface NativeWebSocketSession extends WebSocketSession {
 	 * @return the native session of the required type,
 	 * or {@code null} if not available
 	 */
-	@Nullable
-	<T> T getNativeSession(@Nullable Class<T> requiredType);
+	<T> @Nullable T getNativeSession(@Nullable Class<T> requiredType);
 
 }

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketHandlerAdapter.java

@@ -23,8 +23,8 @@ import org.apache.commons.logging.LogFactory;
 import org.eclipse.jetty.util.BufferUtil;
 import org.eclipse.jetty.websocket.api.Callback;
 import org.eclipse.jetty.websocket.api.Session;
+import org.jspecify.annotations.Nullable;
 
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.BinaryMessage;
 import org.springframework.web.socket.CloseStatus;
@@ -47,8 +47,7 @@ public class JettyWebSocketHandlerAdapter implements Session.Listener {
 
 	private final JettyWebSocketSession wsSession;
 
-	@Nullable
-	private Session nativeSession;
+	private @Nullable Session nativeSession;
 
 
 	public JettyWebSocketHandlerAdapter(WebSocketHandler webSocketHandler, JettyWebSocketSession wsSession) {

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/JettyWebSocketSession.java

@@ -30,9 +30,9 @@ import java.util.concurrent.ExecutionException;
 import org.eclipse.jetty.websocket.api.Callback;
 import org.eclipse.jetty.websocket.api.ExtensionConfig;
 import org.eclipse.jetty.websocket.api.Session;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.socket.BinaryMessage;
@@ -57,20 +57,15 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 
 	private final String id;
 
-	@Nullable
-	private URI uri;
+	private @Nullable URI uri;
 
-	@Nullable
-	private HttpHeaders headers;
+	private @Nullable HttpHeaders headers;
 
-	@Nullable
-	private String acceptedProtocol;
+	private @Nullable String acceptedProtocol;
 
-	@Nullable
-	private List<WebSocketExtension> extensions;
+	private @Nullable List<WebSocketExtension> extensions;
 
-	@Nullable
-	private Principal user;
+	private @Nullable Principal user;
 
 
 	/**
@@ -101,8 +96,7 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 	}
 
 	@Override
-	@Nullable
-	public URI getUri() {
+	public @Nullable URI getUri() {
 		checkNativeSessionInitialized();
 		return this.uri;
 	}
@@ -114,8 +108,7 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 	}
 
 	@Override
-	@Nullable
-	public String getAcceptedProtocol() {
+	public @Nullable String getAcceptedProtocol() {
 		checkNativeSessionInitialized();
 		return this.acceptedProtocol;
 	}
@@ -127,8 +120,7 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 	}
 
 	@Override
-	@Nullable
-	public Principal getPrincipal() {
+	public @Nullable Principal getPrincipal() {
 		return this.user;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Adapter classes for the Jetty WebSocket API.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.adapter.jetty;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/adapter/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Classes adapting Spring's WebSocket API to and from WebSocket providers.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.adapter;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/ConvertingEncoderDecoderSupport.java

@@ -23,6 +23,7 @@ import jakarta.websocket.Decoder;
 import jakarta.websocket.EncodeException;
 import jakarta.websocket.Encoder;
 import jakarta.websocket.EndpointConfig;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -33,7 +34,6 @@ import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.convert.ConversionException;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.ContextLoader;
 
@@ -124,8 +124,7 @@ public abstract class ConvertingEncoderDecoderSupport<T, M> {
 	 * not using {@link ContextLoader}, this method should be overridden.
 	 * @return the {@link ApplicationContext} or {@code null}
 	 */
-	@Nullable
-	protected ApplicationContext getApplicationContext() {
+	protected @Nullable ApplicationContext getApplicationContext() {
 		return ContextLoader.getCurrentWebApplicationContext();
 	}
 
@@ -160,8 +159,7 @@ public abstract class ConvertingEncoderDecoderSupport<T, M> {
 	 * @see jakarta.websocket.Encoder.Binary#encode(Object)
 	 */
 	@SuppressWarnings("unchecked")
-	@Nullable
-	public M encode(T object) throws EncodeException {
+	public @Nullable M encode(T object) throws EncodeException {
 		try {
 			return (M) getConversionService().convert(object, getType(), getMessageType());
 		}
@@ -186,8 +184,7 @@ public abstract class ConvertingEncoderDecoderSupport<T, M> {
 	 * @see jakarta.websocket.Decoder.Binary#decode(ByteBuffer)
 	 */
 	@SuppressWarnings("unchecked")
-	@Nullable
-	public T decode(M message) throws DecodeException {
+	public @Nullable T decode(M message) throws DecodeException {
 		try {
 			return (T) getConversionService().convert(message, getMessageType(), getType());
 		}

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/StandardWebSocketSession.java

@@ -29,9 +29,9 @@ import jakarta.websocket.CloseReason;
 import jakarta.websocket.CloseReason.CloseCodes;
 import jakarta.websocket.Extension;
 import jakarta.websocket.Session;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.socket.BinaryMessage;
@@ -53,25 +53,19 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 
 	private final String id;
 
-	@Nullable
-	private URI uri;
+	private @Nullable URI uri;
 
 	private final HttpHeaders handshakeHeaders;
 
-	@Nullable
-	private String acceptedProtocol;
+	private @Nullable String acceptedProtocol;
 
-	@Nullable
-	private List<WebSocketExtension> extensions;
+	private @Nullable List<WebSocketExtension> extensions;
 
-	@Nullable
-	private Principal user;
+	private @Nullable Principal user;
 
-	@Nullable
-	private final InetSocketAddress localAddress;
+	private final @Nullable InetSocketAddress localAddress;
 
-	@Nullable
-	private final InetSocketAddress remoteAddress;
+	private final @Nullable InetSocketAddress remoteAddress;
 
 
 	/**
@@ -117,8 +111,7 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 	}
 
 	@Override
-	@Nullable
-	public URI getUri() {
+	public @Nullable URI getUri() {
 		checkNativeSessionInitialized();
 		return this.uri;
 	}
@@ -129,8 +122,7 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 	}
 
 	@Override
-	@Nullable
-	public String getAcceptedProtocol() {
+	public @Nullable String getAcceptedProtocol() {
 		checkNativeSessionInitialized();
 		return this.acceptedProtocol;
 	}
@@ -142,20 +134,17 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 	}
 
 	@Override
-	@Nullable
-	public Principal getPrincipal() {
+	public @Nullable Principal getPrincipal() {
 		return this.user;
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getLocalAddress() {
+	public @Nullable InetSocketAddress getLocalAddress() {
 		return this.localAddress;
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getRemoteAddress() {
+	public @Nullable InetSocketAddress getRemoteAddress() {
 		return this.remoteAddress;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/WebSocketToStandardExtensionAdapter.java

@@ -20,8 +20,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 import jakarta.websocket.Extension;
+import org.jspecify.annotations.Nullable;
 
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketExtension;
 
 /**
@@ -47,8 +47,7 @@ public class WebSocketToStandardExtensionAdapter implements Extension {
 					return paramName;
 				}
 				@Override
-				@Nullable
-				public String getValue() {
+				public @Nullable String getValue() {
 					return extension.getParameters().get(paramName);
 				}
 			});

spring-websocket/src/main/java/org/springframework/web/socket/adapter/standard/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Adapter classes for the standard Jakarta WebSocket API.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.adapter.standard;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/client/AbstractWebSocketClient.java

@@ -26,9 +26,9 @@ import java.util.concurrent.CompletableFuture;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.WebSocketExtension;
 import org.springframework.web.socket.WebSocketHandler;

spring-websocket/src/main/java/org/springframework/web/socket/client/WebSocketClient.java

@@ -19,7 +19,8 @@ package org.springframework.web.socket.client;
 import java.net.URI;
 import java.util.concurrent.CompletableFuture;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.WebSocketHttpHeaders;
 import org.springframework.web.socket.WebSocketSession;

spring-websocket/src/main/java/org/springframework/web/socket/client/WebSocketConnectionManager.java

@@ -20,9 +20,10 @@ import java.net.URI;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.Lifecycle;
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.WebSocketHttpHeaders;
 import org.springframework.web.socket.WebSocketSession;
@@ -43,8 +44,7 @@ public class WebSocketConnectionManager extends ConnectionManagerSupport {
 
 	private final WebSocketHandler webSocketHandler;
 
-	@Nullable
-	private WebSocketSession webSocketSession;
+	private @Nullable WebSocketSession webSocketSession;
 
 	private final WebSocketHttpHeaders headers = new WebSocketHttpHeaders();
 
@@ -99,8 +99,7 @@ public class WebSocketConnectionManager extends ConnectionManagerSupport {
 	/**
 	 * Return the configured origin.
 	 */
-	@Nullable
-	public String getOrigin() {
+	public @Nullable String getOrigin() {
 		return this.headers.getOrigin();
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/client/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Client-side abstractions for WebSocket applications.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.client;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/client/standard/AnnotatedEndpointConnectionManager.java

@@ -19,13 +19,13 @@ package org.springframework.web.socket.client.standard;
 import jakarta.websocket.ContainerProvider;
 import jakarta.websocket.Session;
 import jakarta.websocket.WebSocketContainer;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.core.task.TaskExecutor;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.client.ConnectionManagerSupport;
 import org.springframework.web.socket.handler.BeanCreatingHandlerProvider;
@@ -40,18 +40,15 @@ import org.springframework.web.socket.handler.BeanCreatingHandlerProvider;
  */
 public class AnnotatedEndpointConnectionManager extends ConnectionManagerSupport implements BeanFactoryAware {
 
-	@Nullable
-	private final Object endpoint;
+	private final @Nullable Object endpoint;
 
-	@Nullable
-	private final BeanCreatingHandlerProvider<Object> endpointProvider;
+	private final @Nullable BeanCreatingHandlerProvider<Object> endpointProvider;
 
 	private WebSocketContainer webSocketContainer = ContainerProvider.getWebSocketContainer();
 
 	private TaskExecutor taskExecutor = new SimpleAsyncTaskExecutor("AnnotatedEndpointConnectionManager-");
 
-	@Nullable
-	private volatile Session session;
+	private volatile @Nullable Session session;
 
 
 	public AnnotatedEndpointConnectionManager(Object endpoint, String uriTemplate, Object... uriVariables) {

spring-websocket/src/main/java/org/springframework/web/socket/client/standard/EndpointConnectionManager.java

@@ -28,12 +28,12 @@ import jakarta.websocket.Endpoint;
 import jakarta.websocket.Extension;
 import jakarta.websocket.Session;
 import jakarta.websocket.WebSocketContainer;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.core.task.TaskExecutor;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.client.ConnectionManagerSupport;
 import org.springframework.web.socket.handler.BeanCreatingHandlerProvider;
@@ -49,11 +49,9 @@ import org.springframework.web.socket.handler.BeanCreatingHandlerProvider;
  */
 public class EndpointConnectionManager extends ConnectionManagerSupport implements BeanFactoryAware {
 
-	@Nullable
-	private final Endpoint endpoint;
+	private final @Nullable Endpoint endpoint;
 
-	@Nullable
-	private final BeanCreatingHandlerProvider<Endpoint> endpointProvider;
+	private final @Nullable BeanCreatingHandlerProvider<Endpoint> endpointProvider;
 
 	private final ClientEndpointConfig.Builder configBuilder = ClientEndpointConfig.Builder.create();
 
@@ -61,8 +59,7 @@ public class EndpointConnectionManager extends ConnectionManagerSupport implemen
 
 	private TaskExecutor taskExecutor = new SimpleAsyncTaskExecutor("EndpointConnectionManager-");
 
-	@Nullable
-	private volatile Session session;
+	private volatile @Nullable Session session;
 
 
 	public EndpointConnectionManager(Endpoint endpoint, String uriTemplate, Object... uriVariables) {

spring-websocket/src/main/java/org/springframework/web/socket/client/standard/StandardWebSocketClient.java

@@ -37,11 +37,11 @@ import jakarta.websocket.Endpoint;
 import jakarta.websocket.Extension;
 import jakarta.websocket.HandshakeResponse;
 import jakarta.websocket.WebSocketContainer;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.task.AsyncTaskExecutor;
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.concurrent.FutureUtils;
 import org.springframework.web.socket.WebSocketExtension;
@@ -65,11 +65,9 @@ public class StandardWebSocketClient extends AbstractWebSocketClient {
 
 	private final Map<String,Object> userProperties = new HashMap<>();
 
-	@Nullable
-	private SSLContext sslContext;
+	private @Nullable SSLContext sslContext;
 
-	@Nullable
-	private AsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
+	private @Nullable AsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor();
 
 
 	/**
@@ -124,8 +122,7 @@ public class StandardWebSocketClient extends AbstractWebSocketClient {
 	 * Return the {@link SSLContext} to use.
 	 * @since 6.1.3
 	 */
-	@Nullable
-	public SSLContext getSslContext() {
+	public @Nullable SSLContext getSslContext() {
 		return this.sslContext;
 	}
 
@@ -142,8 +139,7 @@ public class StandardWebSocketClient extends AbstractWebSocketClient {
 	/**
 	 * Return the configured {@link AsyncTaskExecutor}.
 	 */
-	@Nullable
-	public AsyncTaskExecutor getTaskExecutor() {
+	public @Nullable AsyncTaskExecutor getTaskExecutor() {
 		return this.taskExecutor;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/client/standard/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Client-side classes for use with standard Jakarta WebSocket endpoints.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.client.standard;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/config/HandlersBeanDefinitionParser.java

@@ -19,6 +19,7 @@ package org.springframework.web.socket.config;
 import java.util.Arrays;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -31,7 +32,6 @@ import org.springframework.beans.factory.support.ManagedMap;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.BeanDefinitionParser;
 import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.util.xml.DomUtils;
@@ -58,8 +58,7 @@ class HandlersBeanDefinitionParser implements BeanDefinitionParser {
 
 
 	@Override
-	@Nullable
-	public BeanDefinition parse(Element element, ParserContext context) {
+	public @Nullable BeanDefinition parse(Element element, ParserContext context) {
 		Object source = context.extractSource(element);
 		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
 		context.pushContainingComponent(compDefinition);

spring-websocket/src/main/java/org/springframework/web/socket/config/MessageBrokerBeanDefinitionParser.java

@@ -21,6 +21,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.MutablePropertyValues;
@@ -38,7 +39,6 @@ import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.BeanDefinitionParser;
 import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.converter.ByteArrayMessageConverter;
 import org.springframework.messaging.converter.CompositeMessageConverter;
 import org.springframework.messaging.converter.DefaultContentTypeResolver;
@@ -133,8 +133,7 @@ class MessageBrokerBeanDefinitionParser implements BeanDefinitionParser {
 
 
 	@Override
-	@Nullable
-	public BeanDefinition parse(Element element, ParserContext context) {
+	public @Nullable BeanDefinition parse(Element element, ParserContext context) {
 		Object source = context.extractSource(element);
 		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);
 		context.pushContainingComponent(compDefinition);
@@ -277,8 +276,7 @@ class MessageBrokerBeanDefinitionParser implements BeanDefinitionParser {
 		return new RuntimeBeanReference(name);
 	}
 
-	@Nullable
-	private RootBeanDefinition getDefaultExecutorBeanDefinition(String channelName) {
+	private @Nullable RootBeanDefinition getDefaultExecutorBeanDefinition(String channelName) {
 		if (channelName.equals("brokerChannel")) {
 			return null;
 		}
@@ -588,8 +586,7 @@ class MessageBrokerBeanDefinitionParser implements BeanDefinitionParser {
 		registerBeanDef(beanDef, context, source);
 	}
 
-	@Nullable
-	private RuntimeBeanReference getValidator(
+	private @Nullable RuntimeBeanReference getValidator(
 			Element messageBrokerElement, @Nullable Object source, ParserContext context) {
 
 		if (messageBrokerElement.hasAttribute("validator")) {

spring-websocket/src/main/java/org/springframework/web/socket/config/WebSocketMessageBrokerStats.java

@@ -25,10 +25,10 @@ import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.core.task.TaskExecutor;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.simp.stomp.StompBrokerRelayMessageHandler;
 import org.springframework.scheduling.SchedulingTaskExecutor;
 import org.springframework.scheduling.TaskScheduler;
@@ -61,26 +61,19 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 	private static final Log logger = LogFactory.getLog(WebSocketMessageBrokerStats.class);
 
 
-	@Nullable
-	private SubProtocolWebSocketHandler webSocketHandler;
+	private @Nullable SubProtocolWebSocketHandler webSocketHandler;
 
-	@Nullable
-	private StompSubProtocolHandler stompSubProtocolHandler;
+	private @Nullable StompSubProtocolHandler stompSubProtocolHandler;
 
-	@Nullable
-	private StompBrokerRelayMessageHandler stompBrokerRelay;
+	private @Nullable StompBrokerRelayMessageHandler stompBrokerRelay;
 
-	@Nullable
-	private TaskExecutor inboundChannelExecutor;
+	private @Nullable TaskExecutor inboundChannelExecutor;
 
-	@Nullable
-	private TaskExecutor outboundChannelExecutor;
+	private @Nullable TaskExecutor outboundChannelExecutor;
 
-	@Nullable
-	private TaskScheduler sockJsTaskScheduler;
+	private @Nullable TaskScheduler sockJsTaskScheduler;
 
-	@Nullable
-	private ScheduledFuture<?> loggingTask;
+	private @Nullable ScheduledFuture<?> loggingTask;
 
 	private long loggingPeriod = TimeUnit.MINUTES.toMillis(30);
 
@@ -132,8 +125,7 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 		this.loggingTask = initLoggingTask(TimeUnit.MINUTES.toMillis(1));
 	}
 
-	@Nullable
-	private StompSubProtocolHandler initStompSubProtocolHandler() {
+	private @Nullable StompSubProtocolHandler initStompSubProtocolHandler() {
 		if (this.webSocketHandler == null) {
 			return null;
 		}
@@ -149,8 +141,7 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 		return null;
 	}
 
-	@Nullable
-	private ScheduledFuture<?> initLoggingTask(long initialDelay) {
+	private @Nullable ScheduledFuture<?> initLoggingTask(long initialDelay) {
 		if (this.sockJsTaskScheduler != null && this.loggingPeriod > 0 && logger.isInfoEnabled()) {
 			return this.sockJsTaskScheduler.scheduleWithFixedDelay(
 					() -> logger.info(WebSocketMessageBrokerStats.this.toString()),
@@ -166,8 +157,7 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 	 * is configured.
 	 * @since 6.2
 	 */
-	@Nullable
-	public SubProtocolWebSocketHandler.Stats getWebSocketSessionStats() {
+	public SubProtocolWebSocketHandler.@Nullable Stats getWebSocketSessionStats() {
 		return (this.webSocketHandler != null ? this.webSocketHandler.getStats() : null);
 	}
 
@@ -176,8 +166,7 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 	 * Can return {@code null} if no {@link SubProtocolHandler} was found.
 	 * @since 6.2
 	 */
-	@Nullable
-	public StompSubProtocolHandler.Stats getStompSubProtocolStats() {
+	public StompSubProtocolHandler.@Nullable Stats getStompSubProtocolStats() {
 		return (this.stompSubProtocolHandler != null ? this.stompSubProtocolHandler.getStats() : null);
 	}
 
@@ -187,8 +176,7 @@ public class WebSocketMessageBrokerStats implements SmartInitializingSingleton {
 	 * is configured.
 	 * @since 6.2
 	 */
-	@Nullable
-	public StompBrokerRelayMessageHandler.Stats getStompBrokerRelayStats() {
+	public StompBrokerRelayMessageHandler.@Nullable Stats getStompBrokerRelayStats() {
 		return (this.stompBrokerRelay != null ? this.stompBrokerRelay.getStats() : null);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/WebSocketNamespaceUtils.java

@@ -19,6 +19,7 @@ package org.springframework.web.socket.config;
 import java.util.Arrays;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -27,7 +28,6 @@ import org.springframework.beans.factory.parsing.BeanComponentDefinition;
 import org.springframework.beans.factory.support.ManagedList;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.util.StringUtils;
 import org.springframework.util.xml.DomUtils;
@@ -64,8 +64,7 @@ abstract class WebSocketNamespaceUtils {
 		return handlerRef;
 	}
 
-	@Nullable
-	public static RuntimeBeanReference registerSockJsService(
+	public static @Nullable RuntimeBeanReference registerSockJsService(
 			Element element, String schedulerName, ParserContext context, @Nullable Object source) {
 
 		Element sockJsElement = DomUtils.getChildElementByTagName(element, "sockjs");

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/AbstractWebSocketHandlerRegistration.java

@@ -20,7 +20,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -47,8 +48,7 @@ public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSock
 
 	private final MultiValueMap<WebSocketHandler, String> handlerMap = new LinkedMultiValueMap<>();
 
-	@Nullable
-	private HandshakeHandler handshakeHandler;
+	private @Nullable HandshakeHandler handshakeHandler;
 
 	private final List<HandshakeInterceptor> interceptors = new ArrayList<>();
 
@@ -56,8 +56,7 @@ public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSock
 
 	private final List<String> allowedOriginPatterns = new ArrayList<>();
 
-	@Nullable
-	private SockJsServiceRegistration sockJsServiceRegistration;
+	private @Nullable SockJsServiceRegistration sockJsServiceRegistration;
 
 
 	@Override
@@ -74,8 +73,7 @@ public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSock
 		return this;
 	}
 
-	@Nullable
-	protected HandshakeHandler getHandshakeHandler() {
+	protected @Nullable HandshakeHandler getHandshakeHandler() {
 		return this.handshakeHandler;
 	}
 
@@ -143,8 +141,7 @@ public abstract class AbstractWebSocketHandlerRegistration<M> implements WebSock
 	 * if the application did not provide one. This should be done prior to
 	 * calling {@link #getMappings()}.
 	 */
-	@Nullable
-	protected SockJsServiceRegistration getSockJsServiceRegistration() {
+	protected @Nullable SockJsServiceRegistration getSockJsServiceRegistration() {
 		return this.sockJsServiceRegistration;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/ServletWebSocketHandlerRegistry.java

@@ -22,7 +22,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.HttpRequestHandler;
@@ -45,8 +46,7 @@ public class ServletWebSocketHandlerRegistry implements WebSocketHandlerRegistry
 
 	private int order = 1;
 
-	@Nullable
-	private UrlPathHelper urlPathHelper;
+	private @Nullable UrlPathHelper urlPathHelper;
 
 
 	public ServletWebSocketHandlerRegistry() {
@@ -82,8 +82,7 @@ public class ServletWebSocketHandlerRegistry implements WebSocketHandlerRegistry
 		this.urlPathHelper = urlPathHelper;
 	}
 
-	@Nullable
-	public UrlPathHelper getUrlPathHelper() {
+	public @Nullable UrlPathHelper getUrlPathHelper() {
 		return this.urlPathHelper;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/SockJsServiceRegistration.java

@@ -20,7 +20,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -41,29 +42,21 @@ import org.springframework.web.socket.sockjs.transport.handler.DefaultSockJsServ
  */
 public class SockJsServiceRegistration {
 
-	@Nullable
-	private TaskScheduler scheduler;
+	private @Nullable TaskScheduler scheduler;
 
-	@Nullable
-	private String clientLibraryUrl;
+	private @Nullable String clientLibraryUrl;
 
-	@Nullable
-	private Integer streamBytesLimit;
+	private @Nullable Integer streamBytesLimit;
 
-	@Nullable
-	private Boolean sessionCookieNeeded;
+	private @Nullable Boolean sessionCookieNeeded;
 
-	@Nullable
-	private Long heartbeatTime;
+	private @Nullable Long heartbeatTime;
 
-	@Nullable
-	private Long disconnectDelay;
+	private @Nullable Long disconnectDelay;
 
-	@Nullable
-	private Integer httpMessageCacheSize;
+	private @Nullable Integer httpMessageCacheSize;
 
-	@Nullable
-	private Boolean webSocketEnabled;
+	private @Nullable Boolean webSocketEnabled;
 
 	private final List<TransportHandler> transportHandlers = new ArrayList<>();
 
@@ -75,11 +68,9 @@ public class SockJsServiceRegistration {
 
 	private final List<String> allowedOriginPatterns = new ArrayList<>();
 
-	@Nullable
-	private Boolean suppressCors;
+	private @Nullable Boolean suppressCors;
 
-	@Nullable
-	private SockJsMessageCodec messageCodec;
+	private @Nullable SockJsMessageCodec messageCodec;
 
 
 	public SockJsServiceRegistration() {
@@ -310,8 +301,7 @@ public class SockJsServiceRegistration {
 	/**
 	 * Return the TaskScheduler, if configured.
 	 */
-	@Nullable
-	protected TaskScheduler getTaskScheduler() {
+	protected @Nullable TaskScheduler getTaskScheduler() {
 		return this.scheduler;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebMvcStompEndpointRegistry.java

@@ -21,8 +21,9 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
@@ -52,8 +53,7 @@ public class WebMvcStompEndpointRegistry implements StompEndpointRegistry {
 
 	private int order = 1;
 
-	@Nullable
-	private UrlPathHelper urlPathHelper;
+	private @Nullable UrlPathHelper urlPathHelper;
 
 	private final SubProtocolWebSocketHandler subProtocolWebSocketHandler;
 
@@ -131,8 +131,7 @@ public class WebMvcStompEndpointRegistry implements StompEndpointRegistry {
 		this.urlPathHelper = urlPathHelper;
 	}
 
-	@Nullable
-	protected UrlPathHelper getUrlPathHelper() {
+	protected @Nullable UrlPathHelper getUrlPathHelper() {
 		return this.urlPathHelper;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebMvcStompWebSocketEndpointRegistration.java

@@ -20,7 +20,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
@@ -51,8 +52,7 @@ public class WebMvcStompWebSocketEndpointRegistration implements StompWebSocketE
 
 	private final TaskScheduler sockJsTaskScheduler;
 
-	@Nullable
-	private HandshakeHandler handshakeHandler;
+	private @Nullable HandshakeHandler handshakeHandler;
 
 	private final List<HandshakeInterceptor> interceptors = new ArrayList<>();
 
@@ -60,8 +60,7 @@ public class WebMvcStompWebSocketEndpointRegistration implements StompWebSocketE
 
 	private final List<String> allowedOriginPatterns = new ArrayList<>();
 
-	@Nullable
-	private SockJsServiceRegistration registration;
+	private @Nullable SockJsServiceRegistration registration;
 
 
 	public WebMvcStompWebSocketEndpointRegistration(

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketConfigurationSupport.java

@@ -16,11 +16,12 @@
 
 package org.springframework.web.socket.config.annotation;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.context.annotation.Bean;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.util.Assert;
@@ -35,8 +36,7 @@ import org.springframework.web.servlet.HandlerMapping;
  */
 public class WebSocketConfigurationSupport {
 
-	@Nullable
-	private ServletWebSocketHandlerRegistry handlerRegistry;
+	private @Nullable ServletWebSocketHandlerRegistry handlerRegistry;
 
 
 	@Bean
@@ -100,15 +100,13 @@ public class WebSocketConfigurationSupport {
 
 	static class DefaultSockJsSchedulerContainer implements InitializingBean, DisposableBean {
 
-		@Nullable
-		private final ThreadPoolTaskScheduler scheduler;
+		private final @Nullable ThreadPoolTaskScheduler scheduler;
 
 		DefaultSockJsSchedulerContainer(@Nullable ThreadPoolTaskScheduler scheduler) {
 			this.scheduler = scheduler;
 		}
 
-		@Nullable
-		public ThreadPoolTaskScheduler getScheduler() {
+		public @Nullable ThreadPoolTaskScheduler getScheduler() {
 			return this.scheduler;
 		}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketMessageBrokerConfigurationSupport.java

@@ -16,13 +16,14 @@
 
 package org.springframework.web.socket.config.annotation;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.beans.factory.config.CustomScopeConfigurer;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.core.task.TaskExecutor;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.converter.MappingJackson2MessageConverter;
 import org.springframework.messaging.simp.SimpMessagingTemplate;
 import org.springframework.messaging.simp.SimpSessionScope;
@@ -59,8 +60,7 @@ import org.springframework.web.socket.server.support.WebSocketHandlerMapping;
  */
 public abstract class WebSocketMessageBrokerConfigurationSupport extends AbstractMessageBrokerConfiguration {
 
-	@Nullable
-	private WebSocketTransportRegistration transportRegistration;
+	private @Nullable WebSocketTransportRegistration transportRegistration;
 
 
 	@Override

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketMessageBrokerConfigurer.java

@@ -18,8 +18,9 @@ package org.springframework.web.socket.config.annotation;
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.SmartLifecycle;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.converter.MessageConverter;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.handler.invocation.HandlerMethodReturnValueHandler;
@@ -123,8 +124,7 @@ public interface WebSocketMessageBrokerConfigurer {
 	 * @since 6.1.4
 	 * @see SmartLifecycle
 	 */
-	@Nullable
-	default Integer getPhase() {
+	default @Nullable Integer getPhase() {
 		return null;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/WebSocketTransportRegistration.java

@@ -20,7 +20,8 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.web.socket.handler.WebSocketHandlerDecoratorFactory;
 
 /**
@@ -31,17 +32,13 @@ import org.springframework.web.socket.handler.WebSocketHandlerDecoratorFactory;
  */
 public class WebSocketTransportRegistration {
 
-	@Nullable
-	private Integer messageSizeLimit;
+	private @Nullable Integer messageSizeLimit;
 
-	@Nullable
-	private Integer sendTimeLimit;
+	private @Nullable Integer sendTimeLimit;
 
-	@Nullable
-	private Integer sendBufferSizeLimit;
+	private @Nullable Integer sendBufferSizeLimit;
 
-	@Nullable
-	private Integer timeToFirstMessage;
+	private @Nullable Integer timeToFirstMessage;
 
 	private final List<WebSocketHandlerDecoratorFactory> decoratorFactories = new ArrayList<>(2);
 
@@ -62,8 +59,7 @@ public class WebSocketTransportRegistration {
 	/**
 	 * Protected accessor for internal use.
 	 */
-	@Nullable
-	protected Integer getMessageSizeLimit() {
+	protected @Nullable Integer getMessageSizeLimit() {
 		return this.messageSizeLimit;
 	}
 
@@ -104,8 +100,7 @@ public class WebSocketTransportRegistration {
 	/**
 	 * Protected accessor for internal use.
 	 */
-	@Nullable
-	protected Integer getSendTimeLimit() {
+	protected @Nullable Integer getSendTimeLimit() {
 		return this.sendTimeLimit;
 	}
 
@@ -141,8 +136,7 @@ public class WebSocketTransportRegistration {
 	/**
 	 * Protected accessor for internal use.
 	 */
-	@Nullable
-	protected Integer getSendBufferSizeLimit() {
+	protected @Nullable Integer getSendBufferSizeLimit() {
 		return this.sendBufferSizeLimit;
 	}
 
@@ -165,8 +159,7 @@ public class WebSocketTransportRegistration {
 	/**
 	 * Protected accessor for internal use.
 	 */
-	@Nullable
-	protected Integer getTimeToFirstMessage() {
+	protected @Nullable Integer getTimeToFirstMessage() {
 		return this.timeToFirstMessage;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/config/annotation/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Support for annotation-based WebSocket setup in configuration classes.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.config.annotation;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/config/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Configuration support for WebSocket request handling.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.config;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/handler/BeanCreatingHandlerProvider.java

@@ -16,11 +16,12 @@
 
 package org.springframework.web.socket.handler;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -36,8 +37,7 @@ public class BeanCreatingHandlerProvider<T> implements BeanFactoryAware {
 
 	private final Class<? extends T> handlerType;
 
-	@Nullable
-	private AutowireCapableBeanFactory beanFactory;
+	private @Nullable AutowireCapableBeanFactory beanFactory;
 
 
 	public BeanCreatingHandlerProvider(Class<? extends T> handlerType) {

spring-websocket/src/main/java/org/springframework/web/socket/handler/ConcurrentWebSocketSessionDecorator.java

@@ -26,8 +26,8 @@ import java.util.function.Consumer;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.WebSocketMessage;
 import org.springframework.web.socket.WebSocketSession;
@@ -56,8 +56,7 @@ public class ConcurrentWebSocketSessionDecorator extends WebSocketSessionDecorat
 
 	private final OverflowStrategy overflowStrategy;
 
-	@Nullable
-	private Consumer<WebSocketMessage<?>> preSendCallback;
+	private @Nullable Consumer<WebSocketMessage<?>> preSendCallback;
 
 
 	private final Queue<WebSocketMessage<?>> buffer = new LinkedBlockingQueue<>();

spring-websocket/src/main/java/org/springframework/web/socket/handler/SessionLimitExceededException.java

@@ -16,7 +16,8 @@
 
 package org.springframework.web.socket.handler;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.web.socket.CloseStatus;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/handler/WebSocketSessionDecorator.java

@@ -23,8 +23,9 @@ import java.security.Principal;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.WebSocketExtension;
@@ -80,8 +81,7 @@ public class WebSocketSessionDecorator implements WebSocketSession {
 	}
 
 	@Override
-	@Nullable
-	public URI getUri() {
+	public @Nullable URI getUri() {
 		return this.delegate.getUri();
 	}
 
@@ -96,26 +96,22 @@ public class WebSocketSessionDecorator implements WebSocketSession {
 	}
 
 	@Override
-	@Nullable
-	public Principal getPrincipal() {
+	public @Nullable Principal getPrincipal() {
 		return this.delegate.getPrincipal();
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getLocalAddress() {
+	public @Nullable InetSocketAddress getLocalAddress() {
 		return this.delegate.getLocalAddress();
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getRemoteAddress() {
+	public @Nullable InetSocketAddress getRemoteAddress() {
 		return this.delegate.getRemoteAddress();
 	}
 
 	@Override
-	@Nullable
-	public String getAcceptedProtocol() {
+	public @Nullable String getAcceptedProtocol() {
 		return this.delegate.getAcceptedProtocol();
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/handler/package-info.java

@@ -2,9 +2,7 @@
  * Convenient {@link org.springframework.web.socket.WebSocketHandler}
  * implementations and decorators.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.handler;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/messaging/AbstractSubProtocolEvent.java

@@ -18,8 +18,9 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationEvent;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.util.Assert;
 
@@ -35,8 +36,7 @@ public abstract class AbstractSubProtocolEvent extends ApplicationEvent {
 
 	private final Message<byte[]> message;
 
-	@Nullable
-	private final Principal user;
+	private final @Nullable Principal user;
 
 
 	/**
@@ -79,8 +79,7 @@ public abstract class AbstractSubProtocolEvent extends ApplicationEvent {
 	/**
 	 * Return the user for the session associated with the event.
 	 */
-	@Nullable
-	public Principal getUser() {
+	public @Nullable Principal getUser() {
 		return this.user;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/messaging/DefaultSimpUserRegistry.java

@@ -22,10 +22,11 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.event.SmartApplicationListener;
 import org.springframework.core.Ordered;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
@@ -152,8 +153,7 @@ public class DefaultSimpUserRegistry implements SimpUserRegistry, SmartApplicati
 	// SimpUserRegistry methods
 
 	@Override
-	@Nullable
-	public SimpUser getUser(String userName) {
+	public @Nullable SimpUser getUser(String userName) {
 		return this.users.get(userName);
 	}
 
@@ -206,9 +206,8 @@ public class DefaultSimpUserRegistry implements SimpUserRegistry, SmartApplicati
 			return this.name;
 		}
 
-		@Nullable
 		@Override
-		public Principal getPrincipal() {
+		public @Nullable Principal getPrincipal() {
 			return this.user;
 		}
 
@@ -218,8 +217,7 @@ public class DefaultSimpUserRegistry implements SimpUserRegistry, SmartApplicati
 		}
 
 		@Override
-		@Nullable
-		public SimpSession getSession(@Nullable String sessionId) {
+		public @Nullable SimpSession getSession(@Nullable String sessionId) {
 			return (sessionId != null ? this.userSessions.get(sessionId) : null);
 		}
 

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SessionConnectEvent.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SessionConnectedEvent.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SessionDisconnectEvent.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SessionSubscribeEvent.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SessionUnsubscribeEvent.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.security.Principal;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/messaging/StompSubProtocolErrorHandler.java

@@ -16,7 +16,8 @@
 
 package org.springframework.web.socket.messaging;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.messaging.simp.stomp.StompCommand;
 import org.springframework.messaging.simp.stomp.StompHeaderAccessor;
@@ -36,8 +37,7 @@ public class StompSubProtocolErrorHandler implements SubProtocolErrorHandler<byt
 
 
 	@Override
-	@Nullable
-	public Message<byte[]> handleClientMessageProcessingError(@Nullable Message<byte[]> clientMessage, Throwable ex) {
+	public @Nullable Message<byte[]> handleClientMessageProcessingError(@Nullable Message<byte[]> clientMessage, Throwable ex) {
 		StompHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.ERROR);
 		accessor.setMessage(ex.getMessage());
 		accessor.setLeaveMutable(true);
@@ -57,8 +57,7 @@ public class StompSubProtocolErrorHandler implements SubProtocolErrorHandler<byt
 	}
 
 	@Override
-	@Nullable
-	public Message<byte[]> handleErrorMessageToClient(Message<byte[]> errorMessage) {
+	public @Nullable Message<byte[]> handleErrorMessageToClient(Message<byte[]> errorMessage) {
 		StompHeaderAccessor accessor = MessageHeaderAccessor.getAccessor(errorMessage, StompHeaderAccessor.class);
 		Assert.notNull(accessor, "No StompHeaderAccessor");
 		if (!accessor.isMutable()) {

spring-websocket/src/main/java/org/springframework/web/socket/messaging/StompSubProtocolHandler.java

@@ -28,11 +28,11 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.simp.SimpAttributes;
@@ -94,8 +94,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 	private static final byte[] EMPTY_PAYLOAD = new byte[0];
 
 
-	@Nullable
-	private StompSubProtocolErrorHandler errorHandler;
+	private @Nullable StompSubProtocolErrorHandler errorHandler;
 
 	private int messageSizeLimit = 64 * 1024;
 
@@ -105,19 +104,15 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 
 	private final Map<String, BufferingStompDecoder> decoders = new ConcurrentHashMap<>();
 
-	@Nullable
-	private MessageHeaderInitializer headerInitializer;
+	private @Nullable MessageHeaderInitializer headerInitializer;
 
-	@Nullable
-	private Map<String, MessageChannel> orderedHandlingMessageChannels;
+	private @Nullable Map<String, MessageChannel> orderedHandlingMessageChannels;
 
 	private final Map<String, Principal> stompAuthentications = new ConcurrentHashMap<>();
 
-	@Nullable
-	private Boolean immutableMessageInterceptorPresent;
+	private @Nullable Boolean immutableMessageInterceptorPresent;
 
-	@Nullable
-	private ApplicationEventPublisher eventPublisher;
+	private @Nullable ApplicationEventPublisher eventPublisher;
 
 	private final DefaultStats stats = new DefaultStats();
 
@@ -136,8 +131,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 	/**
 	 * Return the configured error handler.
 	 */
-	@Nullable
-	public StompSubProtocolErrorHandler getErrorHandler() {
+	public @Nullable StompSubProtocolErrorHandler getErrorHandler() {
 		return this.errorHandler;
 	}
 
@@ -191,8 +185,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 	/**
 	 * Return the configured header initializer.
 	 */
-	@Nullable
-	public MessageHeaderInitializer getHeaderInitializer() {
+	public @Nullable MessageHeaderInitializer getHeaderInitializer() {
 		return this.headerInitializer;
 	}
 
@@ -377,8 +370,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 		}
 	}
 
-	@Nullable
-	private Principal getUser(WebSocketSession session) {
+	private @Nullable Principal getUser(WebSocketSession session) {
 		Principal user = this.stompAuthentications.get(session.getId());
 		return (user != null ? user : session.getPrincipal());
 	}
@@ -619,8 +611,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 		return connectedHeaders;
 	}
 
-	@Nullable
-	private String getDisconnectReceipt(SimpMessageHeaderAccessor simpHeaders) {
+	private @Nullable String getDisconnectReceipt(SimpMessageHeaderAccessor simpHeaders) {
 		String name = StompHeaderAccessor.DISCONNECT_MESSAGE_HEADER;
 		Message<?> message = (Message<?>) simpHeaders.getHeader(name);
 		if (message != null) {
@@ -657,8 +648,7 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 	}
 
 	@Override
-	@Nullable
-	public String resolveSessionId(Message<?> message) {
+	public @Nullable String resolveSessionId(Message<?> message) {
 		return SimpMessageHeaderAccessor.getSessionId(message.getHeaders());
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolErrorHandler.java

@@ -16,7 +16,8 @@
 
 package org.springframework.web.socket.messaging;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 
 /**
@@ -41,8 +42,7 @@ public interface SubProtocolErrorHandler<P> {
 	 * @return the error message to send to the client, or {@code null} in which
 	 * case no message will be sent.
 	 */
-	@Nullable
-	Message<P> handleClientMessageProcessingError(@Nullable Message<P> clientMessage, Throwable ex);
+	@Nullable Message<P> handleClientMessageProcessingError(@Nullable Message<P> clientMessage, Throwable ex);
 
 	/**
 	 * Handle errors sent from the server side to clients, for example, errors from the
@@ -53,7 +53,6 @@ public interface SubProtocolErrorHandler<P> {
 	 * @return the error message to send to the client, or {@code null} in which
 	 * case no message will be sent.
 	 */
-	@Nullable
-	Message<P> handleErrorMessageToClient(Message<P> errorMessage);
+	@Nullable Message<P> handleErrorMessageToClient(Message<P> errorMessage);
 
 }

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolHandler.java

@@ -18,7 +18,8 @@ package org.springframework.web.socket.messaging;
 
 import java.util.List;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.web.socket.CloseStatus;
@@ -67,8 +68,7 @@ public interface SubProtocolHandler {
 	 * Resolve the session id from the given message or return {@code null}.
 	 * @param message the message to resolve the session id from
 	 */
-	@Nullable
-	String resolveSessionId(Message<?> message);
+	@Nullable String resolveSessionId(Message<?> message);
 
 	/**
 	 * Invoked after a {@link WebSocketSession} has started.

spring-websocket/src/main/java/org/springframework/web/socket/messaging/SubProtocolWebSocketHandler.java

@@ -30,9 +30,9 @@ import java.util.concurrent.locks.ReentrantLock;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.SmartLifecycle;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
@@ -86,8 +86,7 @@ public class SubProtocolWebSocketHandler
 
 	private final Set<SubProtocolHandler> protocolHandlers = new LinkedHashSet<>();
 
-	@Nullable
-	private SubProtocolHandler defaultProtocolHandler;
+	private @Nullable SubProtocolHandler defaultProtocolHandler;
 
 	private final Map<String, WebSocketSessionHolder> sessions = new ConcurrentHashMap<>();
 
@@ -103,8 +102,7 @@ public class SubProtocolWebSocketHandler
 
 	private final DefaultStats stats = new DefaultStats();
 
-	@Nullable
-	private Integer phase;
+	private @Nullable Integer phase;
 
 	private volatile boolean running;
 
@@ -184,8 +182,7 @@ public class SubProtocolWebSocketHandler
 	/**
 	 * Return the default sub-protocol handler to use.
 	 */
-	@Nullable
-	public SubProtocolHandler getDefaultProtocolHandler() {
+	public @Nullable SubProtocolHandler getDefaultProtocolHandler() {
 		return this.defaultProtocolHandler;
 	}
 
@@ -477,8 +474,7 @@ public class SubProtocolWebSocketHandler
 		return handler;
 	}
 
-	@Nullable
-	private String resolveSessionId(Message<?> message) {
+	private @Nullable String resolveSessionId(Message<?> message) {
 		for (SubProtocolHandler handler : this.protocolHandlerLookup.values()) {
 			String sessionId = handler.resolveSessionId(message);
 			if (sessionId != null) {

spring-websocket/src/main/java/org/springframework/web/socket/messaging/WebSocketAnnotationMethodMessageHandler.java

@@ -19,8 +19,9 @@ package org.springframework.web.socket.messaging;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.SubscribableChannel;
 import org.springframework.messaging.handler.MessagingAdviceBean;
@@ -100,8 +101,7 @@ public class WebSocketAnnotationMethodMessageHandler extends SimpAnnotationMetho
 		}
 
 		@Override
-		@Nullable
-		public Class<?> getBeanType() {
+		public @Nullable Class<?> getBeanType() {
 			return this.adviceBean.getBeanType();
 		}
 

spring-websocket/src/main/java/org/springframework/web/socket/messaging/WebSocketStompClient.java

@@ -29,10 +29,10 @@ import java.util.function.BiConsumer;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.context.SmartLifecycle;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.simp.stomp.BufferingStompDecoder;
 import org.springframework.messaging.simp.stomp.ConnectionHandlingStompSession;
@@ -81,8 +81,7 @@ public class WebSocketStompClient extends StompClientSupport implements SmartLif
 
 	private int inboundMessageSizeLimit = 64 * 1024;
 
-	@Nullable
-	private Integer outboundMessageSizeLimit;
+	private @Nullable Integer outboundMessageSizeLimit;
 
 	private boolean autoStartup = true;
 
@@ -157,8 +156,7 @@ public class WebSocketStompClient extends StompClientSupport implements SmartLif
 	 * Get the configured outbound message buffer size in bytes.
 	 * @since 6.2
 	 */
-	@Nullable
-	public Integer getOutboundMessageSizeLimit() {
+	public @Nullable Integer getOutboundMessageSizeLimit() {
 		return this.outboundMessageSizeLimit;
 	}
 
@@ -323,18 +321,15 @@ public class WebSocketStompClient extends StompClientSupport implements SmartLif
 		private final StompWebSocketMessageCodec codec =
 				new StompWebSocketMessageCodec(getInboundMessageSizeLimit(),getOutboundMessageSizeLimit());
 
-		@Nullable
-		private volatile WebSocketSession session;
+		private volatile @Nullable WebSocketSession session;
 
 		private volatile long lastReadTime = -1;
 
 		private volatile long lastWriteTime = -1;
 
-		@Nullable
-		private ScheduledFuture<?> readInactivityFuture;
+		private @Nullable ScheduledFuture<?> readInactivityFuture;
 
-		@Nullable
-		private ScheduledFuture<?> writeInactivityFuture;
+		private @Nullable ScheduledFuture<?> writeInactivityFuture;
 
 		public WebSocketTcpConnectionHandlerAdapter(TcpConnectionHandler<byte[]> stompSession) {
 			Assert.notNull(stompSession, "TcpConnectionHandler must not be null");
@@ -516,8 +511,7 @@ public class WebSocketStompClient extends StompClientSupport implements SmartLif
 
 		private final BufferingStompDecoder bufferingDecoder;
 
-		@Nullable
-		private final SplittingStompEncoder splittingEncoder;
+		private final @Nullable SplittingStompEncoder splittingEncoder;
 
 		public StompWebSocketMessageCodec(int inboundMessageSizeLimit, @Nullable Integer outboundMessageSizeLimit) {
 			this.bufferingDecoder = new BufferingStompDecoder(DECODER, inboundMessageSizeLimit);

spring-websocket/src/main/java/org/springframework/web/socket/messaging/package-info.java

@@ -1,9 +1,7 @@
 /**
  * WebSocket integration for Spring's messaging module.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.messaging;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Common abstractions and Spring configuration support for WebSocket applications.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/server/HandshakeInterceptor.java

@@ -18,9 +18,10 @@ package org.springframework.web.socket.server;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketHandler;
 
 /**

spring-websocket/src/main/java/org/springframework/web/socket/server/RequestUpgradeStrategy.java

@@ -20,9 +20,10 @@ import java.security.Principal;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketExtension;
 import org.springframework.web.socket.WebSocketHandler;
 

spring-websocket/src/main/java/org/springframework/web/socket/server/jetty/JettyRequestUpgradeStrategy.java

@@ -29,12 +29,12 @@ import jakarta.servlet.http.HttpServletResponse;
 import org.eclipse.jetty.ee10.websocket.server.JettyWebSocketCreator;
 import org.eclipse.jetty.ee10.websocket.server.JettyWebSocketServerContainer;
 import org.eclipse.jetty.websocket.api.Configurable;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
 import org.springframework.http.server.ServletServerHttpRequest;
 import org.springframework.http.server.ServletServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.ServletContextAware;
 import org.springframework.web.socket.WebSocketExtension;
@@ -55,8 +55,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Serv
 	private static final String[] SUPPORTED_VERSIONS = new String[] {"13"};
 
 
-	@Nullable
-	private Consumer<Configurable> webSocketConfigurer;
+	private @Nullable Consumer<Configurable> webSocketConfigurer;
 
 
 	@Override

spring-websocket/src/main/java/org/springframework/web/socket/server/jetty/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Server-side support for the Jetty WebSocket API.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.server.jetty;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/server/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Server-side abstractions for WebSocket interactions.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.server;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/ServerEndpointExporter.java

@@ -27,11 +27,11 @@ import jakarta.websocket.DeploymentException;
 import jakarta.websocket.server.ServerContainer;
 import jakarta.websocket.server.ServerEndpoint;
 import jakarta.websocket.server.ServerEndpointConfig;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.context.ApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.support.WebApplicationObjectSupport;
 
@@ -56,11 +56,9 @@ import org.springframework.web.context.support.WebApplicationObjectSupport;
 public class ServerEndpointExporter extends WebApplicationObjectSupport
 		implements InitializingBean, SmartInitializingSingleton {
 
-	@Nullable
-	private List<Class<?>> annotatedEndpointClasses;
+	private @Nullable List<Class<?>> annotatedEndpointClasses;
 
-	@Nullable
-	private ServerContainer serverContainer;
+	private @Nullable ServerContainer serverContainer;
 
 
 	/**
@@ -84,8 +82,7 @@ public class ServerEndpointExporter extends WebApplicationObjectSupport
 	/**
 	 * Return the JSR-356 {@link ServerContainer} to use for endpoint registration.
 	 */
-	@Nullable
-	protected ServerContainer getServerContainer() {
+	protected @Nullable ServerContainer getServerContainer() {
 		return this.serverContainer;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/ServerEndpointRegistration.java

@@ -28,10 +28,10 @@ import jakarta.websocket.Extension;
 import jakarta.websocket.HandshakeResponse;
 import jakarta.websocket.server.HandshakeRequest;
 import jakarta.websocket.server.ServerEndpointConfig;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.handler.BeanCreatingHandlerProvider;
 
@@ -59,11 +59,9 @@ public class ServerEndpointRegistration extends ServerEndpointConfig.Configurato
 
 	private final String path;
 
-	@Nullable
-	private final Endpoint endpoint;
+	private final @Nullable Endpoint endpoint;
 
-	@Nullable
-	private final BeanCreatingHandlerProvider<Endpoint> endpointProvider;
+	private final @Nullable BeanCreatingHandlerProvider<Endpoint> endpointProvider;
 
 	private List<String> subprotocols = new ArrayList<>(0);
 

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/ServletServerContainerFactoryBean.java

@@ -19,10 +19,10 @@ package org.springframework.web.socket.server.standard;
 import jakarta.servlet.ServletContext;
 import jakarta.websocket.WebSocketContainer;
 import jakarta.websocket.server.ServerContainer;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.ServletContextAware;
 
@@ -47,63 +47,53 @@ import org.springframework.web.context.ServletContextAware;
 public class ServletServerContainerFactoryBean
 		implements FactoryBean<WebSocketContainer>, ServletContextAware, InitializingBean {
 
-	@Nullable
-	private Long asyncSendTimeout;
+	private @Nullable Long asyncSendTimeout;
 
-	@Nullable
-	private Long maxSessionIdleTimeout;
+	private @Nullable Long maxSessionIdleTimeout;
 
-	@Nullable
-	private Integer maxTextMessageBufferSize;
+	private @Nullable Integer maxTextMessageBufferSize;
 
-	@Nullable
-	private Integer maxBinaryMessageBufferSize;
+	private @Nullable Integer maxBinaryMessageBufferSize;
 
-	@Nullable
-	private ServletContext servletContext;
+	private @Nullable ServletContext servletContext;
 
-	@Nullable
-	private ServerContainer serverContainer;
+	private @Nullable ServerContainer serverContainer;
 
 
-	public void setAsyncSendTimeout(Long timeoutInMillis) {
+	public void setAsyncSendTimeout(@Nullable Long timeoutInMillis) {
 		this.asyncSendTimeout = timeoutInMillis;
 	}
 
-	@Nullable
-	public Long getAsyncSendTimeout() {
+	public @Nullable Long getAsyncSendTimeout() {
 		return this.asyncSendTimeout;
 	}
 
-	public void setMaxSessionIdleTimeout(Long timeoutInMillis) {
+	public void setMaxSessionIdleTimeout(@Nullable Long timeoutInMillis) {
 		this.maxSessionIdleTimeout = timeoutInMillis;
 	}
 
-	@Nullable
-	public Long getMaxSessionIdleTimeout() {
+	public @Nullable Long getMaxSessionIdleTimeout() {
 		return this.maxSessionIdleTimeout;
 	}
 
-	public void setMaxTextMessageBufferSize(Integer bufferSize) {
+	public void setMaxTextMessageBufferSize(@Nullable Integer bufferSize) {
 		this.maxTextMessageBufferSize = bufferSize;
 	}
 
-	@Nullable
-	public Integer getMaxTextMessageBufferSize() {
+	public @Nullable Integer getMaxTextMessageBufferSize() {
 		return this.maxTextMessageBufferSize;
 	}
 
-	public void setMaxBinaryMessageBufferSize(Integer bufferSize) {
+	public void setMaxBinaryMessageBufferSize(@Nullable Integer bufferSize) {
 		this.maxBinaryMessageBufferSize = bufferSize;
 	}
 
-	@Nullable
-	public Integer getMaxBinaryMessageBufferSize() {
+	public @Nullable Integer getMaxBinaryMessageBufferSize() {
 		return this.maxBinaryMessageBufferSize;
 	}
 
 	@Override
-	public void setServletContext(ServletContext servletContext) {
+	public void setServletContext(@Nullable ServletContext servletContext) {
 		this.servletContext = servletContext;
 	}
 
@@ -133,8 +123,7 @@ public class ServletServerContainerFactoryBean
 
 
 	@Override
-	@Nullable
-	public ServerContainer getObject() {
+	public @Nullable ServerContainer getObject() {
 		return this.serverContainer;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/SpringConfigurator.java

@@ -24,9 +24,9 @@ import jakarta.websocket.server.ServerEndpoint;
 import jakarta.websocket.server.ServerEndpointConfig.Configurator;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.annotation.AnnotationUtils;
-import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Component;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
@@ -98,8 +98,7 @@ public class SpringConfigurator extends Configurator {
 		return wac.getAutowireCapableBeanFactory().createBean(endpointClass);
 	}
 
-	@Nullable
-	private String getBeanNameByType(WebApplicationContext wac, Class<?> endpointClass) {
+	private @Nullable String getBeanNameByType(WebApplicationContext wac, Class<?> endpointClass) {
 		String wacId = wac.getId();
 
 		Map<Class<?>, String> beanNamesByType = cache.computeIfAbsent(wacId, k -> new ConcurrentHashMap<>());

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/StandardWebSocketUpgradeStrategy.java

@@ -29,13 +29,13 @@ import jakarta.servlet.http.HttpServletResponse;
 import jakarta.websocket.Extension;
 import jakarta.websocket.WebSocketContainer;
 import jakarta.websocket.server.ServerContainer;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
 import org.springframework.http.server.ServletServerHttpRequest;
 import org.springframework.http.server.ServletServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.WebSocketExtension;
 import org.springframework.web.socket.WebSocketHandler;
@@ -63,8 +63,7 @@ public class StandardWebSocketUpgradeStrategy implements RequestUpgradeStrategy
 
 	private static final String[] SUPPORTED_VERSIONS = new String[] {"13"};
 
-	@Nullable
-	private volatile List<WebSocketExtension> extensions;
+	private volatile @Nullable List<WebSocketExtension> extensions;
 
 
 	@Override

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Server-side classes for use with standard JSR-356 WebSocket endpoints.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.server.standard;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/server/support/AbstractHandshakeHandler.java

@@ -28,6 +28,7 @@ import java.util.Map;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.core.log.LogFormatUtils;
@@ -35,7 +36,6 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 import org.springframework.web.socket.SubProtocolCapable;
@@ -285,8 +285,7 @@ public abstract class AbstractHandshakeHandler implements HandshakeHandler, Life
 	 * @return the selected protocols or {@code null}
 	 * @see #determineHandlerSupportedProtocols(WebSocketHandler)
 	 */
-	@Nullable
-	protected String selectProtocol(List<String> requestedProtocols, WebSocketHandler webSocketHandler) {
+	protected @Nullable String selectProtocol(List<String> requestedProtocols, WebSocketHandler webSocketHandler) {
 		List<String> handlerProtocols = determineHandlerSupportedProtocols(webSocketHandler);
 		for (String protocol : requestedProtocols) {
 			if (handlerProtocols.contains(protocol.toLowerCase(Locale.ROOT))) {
@@ -346,8 +345,7 @@ public abstract class AbstractHandshakeHandler implements HandshakeHandler, Life
 	 * @param attributes handshake attributes to pass to the WebSocket session
 	 * @return the user for the WebSocket session, or {@code null} if not available
 	 */
-	@Nullable
-	protected Principal determineUser(
+	protected @Nullable Principal determineUser(
 			ServerHttpRequest request, WebSocketHandler wsHandler, Map<String, Object> attributes) {
 
 		return request.getPrincipal();

spring-websocket/src/main/java/org/springframework/web/socket/server/support/HandshakeInterceptorChain.java

@@ -22,10 +22,10 @@ import java.util.Map;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.server.HandshakeInterceptor;
 

spring-websocket/src/main/java/org/springframework/web/socket/server/support/HttpSessionHandshakeInterceptor.java

@@ -22,11 +22,11 @@ import java.util.Enumeration;
 import java.util.Map;
 
 import jakarta.servlet.http.HttpSession;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
 import org.springframework.http.server.ServletServerHttpRequest;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.WebSocketSession;
 import org.springframework.web.socket.server.HandshakeInterceptor;
@@ -162,8 +162,7 @@ public class HttpSessionHandshakeInterceptor implements HandshakeInterceptor {
 		return true;
 	}
 
-	@Nullable
-	private HttpSession getSession(ServerHttpRequest request) {
+	private @Nullable HttpSession getSession(ServerHttpRequest request) {
 		if (request instanceof ServletServerHttpRequest serverRequest) {
 			return serverRequest.getServletRequest().getSession(isCreateSession());
 		}

spring-websocket/src/main/java/org/springframework/web/socket/server/support/OriginHandshakeInterceptor.java

@@ -25,11 +25,11 @@ import java.util.Map;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpStatus;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.cors.CorsConfiguration;

spring-websocket/src/main/java/org/springframework/web/socket/server/support/WebSocketHandlerMapping.java

@@ -18,12 +18,12 @@ package org.springframework.web.socket.server.support;
 
 import jakarta.servlet.ServletContext;
 import jakarta.servlet.http.HttpServletRequest;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.context.SmartLifecycle;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
-import org.springframework.lang.Nullable;
 import org.springframework.web.context.ServletContextAware;
 import org.springframework.web.servlet.HandlerExecutionChain;
 import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
@@ -41,8 +41,7 @@ public class WebSocketHandlerMapping extends SimpleUrlHandlerMapping implements
 
 	private boolean webSocketUpgradeMatch;
 
-	@Nullable
-	private Integer phase;
+	private @Nullable Integer phase;
 
 	private volatile boolean running;
 
@@ -118,8 +117,7 @@ public class WebSocketHandlerMapping extends SimpleUrlHandlerMapping implements
 
 
 	@Override
-	@Nullable
-	protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
+	protected @Nullable Object getHandlerInternal(HttpServletRequest request) throws Exception {
 		Object handler = super.getHandlerInternal(request);
 		return (matchWebSocketUpgrade(handler, request) ? handler : null);
 	}

spring-websocket/src/main/java/org/springframework/web/socket/server/support/WebSocketHttpRequestHandler.java

@@ -28,13 +28,13 @@ import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
 import org.springframework.http.server.ServletServerHttpRequest;
 import org.springframework.http.server.ServletServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.HttpRequestHandler;
 import org.springframework.web.context.ServletContextAware;

spring-websocket/src/main/java/org/springframework/web/socket/server/support/package-info.java

@@ -2,9 +2,7 @@
  * Server-side support classes including container-specific strategies
  * for upgrading a request.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.server.support;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/SockJsException.java

@@ -16,8 +16,9 @@
 
 package org.springframework.web.socket.sockjs;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.NestedRuntimeException;
-import org.springframework.lang.Nullable;
 
 /**
  * Base class for exceptions raised while processing SockJS HTTP requests.
@@ -28,8 +29,7 @@ import org.springframework.lang.Nullable;
 @SuppressWarnings("serial")
 public class SockJsException extends NestedRuntimeException {
 
-	@Nullable
-	private final String sessionId;
+	private final @Nullable String sessionId;
 
 
 	/**
@@ -56,8 +56,7 @@ public class SockJsException extends NestedRuntimeException {
 	/**
 	 * Return the SockJS session id.
 	 */
-	@Nullable
-	public String getSockJsSessionId() {
+	public @Nullable String getSockJsSessionId() {
 		return this.sessionId;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/SockJsService.java

@@ -16,9 +16,10 @@
 
 package org.springframework.web.socket.sockjs;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.handler.ExceptionWebSocketHandlerDecorator;
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/SockJsTransportFailureException.java

@@ -16,7 +16,7 @@
 
 package org.springframework.web.socket.sockjs;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Indicates a serious failure that occurred in the SockJS implementation as opposed to

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/AbstractClientSockJsSession.java

@@ -25,9 +25,9 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.TextMessage;
@@ -61,11 +61,9 @@ public abstract class AbstractClientSockJsSession implements WebSocketSession {
 
 	private final Map<String, Object> attributes = new ConcurrentHashMap<>();
 
-	@Nullable
-	private volatile State state = State.NEW;
+	private volatile @Nullable State state = State.NEW;
 
-	@Nullable
-	private volatile CloseStatus closeStatus;
+	private volatile @Nullable CloseStatus closeStatus;
 
 
 	protected AbstractClientSockJsSession(TransportRequest request, WebSocketHandler handler,
@@ -101,8 +99,7 @@ public abstract class AbstractClientSockJsSession implements WebSocketSession {
 	}
 
 	@Override
-	@Nullable
-	public Principal getPrincipal() {
+	public @Nullable Principal getPrincipal() {
 		return this.request.getUser();
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/AbstractXhrTransport.java

@@ -24,11 +24,11 @@ import java.util.concurrent.CompletableFuture;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
-import org.springframework.lang.Nullable;
 import org.springframework.web.client.HttpServerErrorException;
 import org.springframework.web.socket.TextMessage;
 import org.springframework.web.socket.WebSocketHandler;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/DefaultTransportRequest.java

@@ -28,9 +28,9 @@ import java.util.function.BiConsumer;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.WebSocketHandler;
@@ -62,18 +62,15 @@ class DefaultTransportRequest implements TransportRequest {
 
 	private final SockJsMessageCodec codec;
 
-	@Nullable
-	private Principal user;
+	private @Nullable Principal user;
 
 	private long timeoutValue;
 
-	@Nullable
-	private TaskScheduler timeoutScheduler;
+	private @Nullable TaskScheduler timeoutScheduler;
 
 	private final List<Runnable> timeoutTasks = new ArrayList<>();
 
-	@Nullable
-	private DefaultTransportRequest fallbackRequest;
+	private @Nullable DefaultTransportRequest fallbackRequest;
 
 
 	public DefaultTransportRequest(SockJsUrlInfo sockJsUrlInfo,
@@ -118,8 +115,7 @@ class DefaultTransportRequest implements TransportRequest {
 	}
 
 	@Override
-	@Nullable
-	public Principal getUser() {
+	public @Nullable Principal getUser() {
 		return this.user;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/InfoReceiver.java

@@ -18,8 +18,9 @@ package org.springframework.web.socket.sockjs.client;
 
 import java.net.URI;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 
 /**
  * A component that can execute the SockJS "Info" request that needs to be

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/JettyXhrTransport.java

@@ -29,12 +29,12 @@ import org.eclipse.jetty.client.Response;
 import org.eclipse.jetty.client.StringRequestContent;
 import org.eclipse.jetty.http.HttpFields;
 import org.eclipse.jetty.http.HttpMethod;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatusCode;
 import org.springframework.http.ResponseEntity;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StreamUtils;
 import org.springframework.web.client.HttpServerErrorException;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/RestTemplateXhrTransport.java

@@ -22,6 +22,8 @@ import java.io.InputStream;
 import java.net.URI;
 import java.util.concurrent.CompletableFuture;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.core.task.TaskExecutor;
 import org.springframework.http.HttpHeaders;
@@ -32,7 +34,6 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.http.StreamingHttpOutputMessage;
 import org.springframework.http.client.ClientHttpRequest;
 import org.springframework.http.client.ClientHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StreamUtils;
 import org.springframework.web.client.HttpServerErrorException;
@@ -167,8 +168,7 @@ public class RestTemplateXhrTransport extends AbstractXhrTransport {
 
 		private final HttpHeaders headers;
 
-		@Nullable
-		private final String body;
+		private final @Nullable String body;
 
 		public XhrRequestCallback(HttpHeaders headers) {
 			this(headers, null);
@@ -207,8 +207,7 @@ public class RestTemplateXhrTransport extends AbstractXhrTransport {
 		}
 
 		@Override
-		@Nullable
-		public Object extractData(ClientHttpResponse response) throws IOException {
+		public @Nullable Object extractData(ClientHttpResponse response) throws IOException {
 			HttpStatusCode httpStatus = response.getStatusCode();
 			if (httpStatus != HttpStatus.OK) {
 				throw new HttpServerErrorException(

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/SockJsClient.java

@@ -27,10 +27,10 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.context.Lifecycle;
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -72,16 +72,13 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 
 	private final List<Transport> transports;
 
-	@Nullable
-	private String[] httpHeaderNames;
+	private String @Nullable [] httpHeaderNames;
 
 	private InfoReceiver infoReceiver;
 
-	@Nullable
-	private SockJsMessageCodec messageCodec;
+	private @Nullable SockJsMessageCodec messageCodec;
 
-	@Nullable
-	private TaskScheduler connectTimeoutScheduler;
+	private @Nullable TaskScheduler connectTimeoutScheduler;
 
 	private volatile boolean running;
 
@@ -125,7 +122,7 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 	 * headers (for example, auth headers) to be used for other HTTP requests.
 	 * @param httpHeaderNames the HTTP header names
 	 */
-	public void setHttpHeaderNames(@Nullable String... httpHeaderNames) {
+	public void setHttpHeaderNames(String @Nullable ... httpHeaderNames) {
 		this.httpHeaderNames = httpHeaderNames;
 	}
 
@@ -133,8 +130,7 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 	 * The configured HTTP header names to be copied from the handshake
 	 * headers and also included in other HTTP requests.
 	 */
-	@Nullable
-	public String[] getHttpHeaderNames() {
+	public String @Nullable [] getHttpHeaderNames() {
 		return this.httpHeaderNames;
 	}
 
@@ -268,8 +264,7 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 		return new SockJsUrlInfo(url);
 	}
 
-	@Nullable
-	private HttpHeaders getHttpRequestHeaders(@Nullable HttpHeaders webSocketHttpHeaders) {
+	private @Nullable HttpHeaders getHttpRequestHeaders(@Nullable HttpHeaders webSocketHttpHeaders) {
 		if (getHttpHeaderNames() == null || webSocketHttpHeaders == null) {
 			return webSocketHttpHeaders;
 		}
@@ -335,8 +330,7 @@ public class SockJsClient implements WebSocketClient, Lifecycle {
 	 * <p>By default this method returns {@code null}.
 	 * @return the user to associate with the session (possibly {@code null})
 	 */
-	@Nullable
-	protected Principal getUser() {
+	protected @Nullable Principal getUser() {
 		return null;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/SockJsUrlInfo.java

@@ -19,7 +19,8 @@ package org.springframework.web.socket.sockjs.client;
 import java.net.URI;
 import java.util.UUID;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.IdGenerator;
 import org.springframework.util.JdkIdGenerator;
 import org.springframework.util.StringUtils;
@@ -42,14 +43,11 @@ public class SockJsUrlInfo {
 
 	private final URI sockJsUrl;
 
-	@Nullable
-	private String serverId;
+	private @Nullable String serverId;
 
-	@Nullable
-	private String sessionId;
+	private @Nullable String sessionId;
 
-	@Nullable
-	private UUID uuid;
+	private @Nullable UUID uuid;
 
 
 	/**

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/TransportRequest.java

@@ -19,8 +19,9 @@ package org.springframework.web.socket.sockjs.client;
 import java.net.URI;
 import java.security.Principal;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.web.socket.sockjs.frame.SockJsMessageCodec;
 
 /**
@@ -63,8 +64,7 @@ public interface TransportRequest {
 	/**
 	 * Return the user associated with the request, if any.
 	 */
-	@Nullable
-	Principal getUser();
+	@Nullable Principal getUser();
 
 	/**
 	 * Return the message codec to use for encoding SockJS messages.

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/UndertowXhrTransport.java

@@ -39,6 +39,7 @@ import io.undertow.util.HeaderMap;
 import io.undertow.util.HttpString;
 import io.undertow.util.Methods;
 import io.undertow.util.StringReadChannelListener;
+import org.jspecify.annotations.Nullable;
 import org.xnio.ChannelListener;
 import org.xnio.ChannelListeners;
 import org.xnio.IoUtils;
@@ -52,7 +53,6 @@ import org.xnio.channels.StreamSourceChannel;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatusCode;
 import org.springframework.http.ResponseEntity;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StreamUtils;
 import org.springframework.util.StringUtils;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/WebSocketClientSockJsSession.java

@@ -21,7 +21,8 @@ import java.net.InetSocketAddress;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.TextMessage;
@@ -39,8 +40,7 @@ import org.springframework.web.socket.adapter.NativeWebSocketSession;
  */
 public class WebSocketClientSockJsSession extends AbstractClientSockJsSession implements NativeWebSocketSession {
 
-	@Nullable
-	private WebSocketSession webSocketSession;
+	private @Nullable WebSocketSession webSocketSession;
 
 
 	public WebSocketClientSockJsSession(TransportRequest request, WebSocketHandler handler,
@@ -58,28 +58,24 @@ public class WebSocketClientSockJsSession extends AbstractClientSockJsSession im
 
 	@SuppressWarnings("unchecked")
 	@Override
-	@Nullable
-	public <T> T getNativeSession(@Nullable Class<T> requiredType) {
+	public <T> @Nullable T getNativeSession(@Nullable Class<T> requiredType) {
 		return (requiredType == null || requiredType.isInstance(this.webSocketSession) ? (T) this.webSocketSession : null);
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getLocalAddress() {
+	public @Nullable InetSocketAddress getLocalAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getLocalAddress();
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getRemoteAddress() {
+	public @Nullable InetSocketAddress getRemoteAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getRemoteAddress();
 	}
 
 	@Override
-	@Nullable
-	public String getAcceptedProtocol() {
+	public @Nullable String getAcceptedProtocol() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getAcceptedProtocol();
 	}

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/XhrClientSockJsSession.java

@@ -22,9 +22,10 @@ import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.TextMessage;
@@ -78,21 +79,18 @@ public class XhrClientSockJsSession extends AbstractClientSockJsSession {
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getLocalAddress() {
+	public @Nullable InetSocketAddress getLocalAddress() {
 		return null;
 	}
 
 	@Override
-	@Nullable
-	public InetSocketAddress getRemoteAddress() {
+	public @Nullable InetSocketAddress getRemoteAddress() {
 		URI uri = getUri();
 		return (uri != null ? new InetSocketAddress(uri.getHost(), uri.getPort()) : null);
 	}
 
 	@Override
-	@Nullable
-	public String getAcceptedProtocol() {
+	public @Nullable String getAcceptedProtocol() {
 		return null;
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/package-info.java

@@ -2,9 +2,7 @@
  * SockJS client implementation of
  * {@link org.springframework.web.socket.client.WebSocketClient}.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.sockjs.client;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/frame/Jackson2SockJsMessageCodec.java

@@ -23,9 +23,9 @@ import com.fasterxml.jackson.core.io.JsonStringEncoder;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.MapperFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -56,14 +56,12 @@ public class Jackson2SockJsMessageCodec extends AbstractSockJsMessageCodec {
 
 
 	@Override
-	@Nullable
-	public String[] decode(String content) throws IOException {
+	public String @Nullable [] decode(String content) throws IOException {
 		return this.objectMapper.readValue(content, String[].class);
 	}
 
 	@Override
-	@Nullable
-	public String[] decodeInputStream(InputStream content) throws IOException {
+	public String @Nullable [] decodeInputStream(InputStream content) throws IOException {
 		return this.objectMapper.readValue(content, String[].class);
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/frame/SockJsFrame.java

@@ -19,7 +19,8 @@ package org.springframework.web.socket.sockjs.frame;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -109,8 +110,7 @@ public class SockJsFrame {
 	 * for SockJS "open" and "close" frames, which do not contain data, return
 	 * {@code null}.
 	 */
-	@Nullable
-	public String getFrameData() {
+	public @Nullable String getFrameData() {
 		if (getType() == SockJsFrameType.OPEN || getType() == SockJsFrameType.HEARTBEAT) {
 			return null;
 		}

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/frame/SockJsMessageCodec.java

@@ -19,7 +19,7 @@ package org.springframework.web.socket.sockjs.frame;
 import java.io.IOException;
 import java.io.InputStream;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Encode and decode messages to and from a SockJS message frame,
@@ -50,8 +50,7 @@ public interface SockJsMessageCodec {
 	 * @return an array of messages, or {@code null} if none
 	 * @throws IOException if the content could not be parsed
 	 */
-	@Nullable
-	String[] decode(String content) throws IOException;
+	String @Nullable [] decode(String content) throws IOException;
 
 	/**
 	 * Decode the given SockJS message frame.
@@ -59,7 +58,6 @@ public interface SockJsMessageCodec {
 	 * @return an array of messages, or {@code null} if none
 	 * @throws IOException if the content could not be parsed
 	 */
-	@Nullable
-	String[] decodeInputStream(InputStream content) throws IOException;
+	String @Nullable [] decodeInputStream(InputStream content) throws IOException;
 
 }

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/frame/package-info.java

@@ -2,9 +2,7 @@
  * Support classes for creating SockJS frames including the encoding and decoding
  * of SockJS message frames.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.sockjs.frame;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/package-info.java

@@ -1,9 +1,7 @@
 /**
  * Top-level SockJS types.
  */
-@NonNullApi
-@NonNullFields
+@NullMarked
 package org.springframework.web.socket.sockjs;
 
-import org.springframework.lang.NonNullApi;
-import org.springframework.lang.NonNullFields;
+import org.jspecify.annotations.NullMarked;

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/support/AbstractSockJsService.java

@@ -31,6 +31,7 @@ import java.util.concurrent.TimeUnit;
 import jakarta.servlet.http.HttpServletRequest;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.log.LogFormatUtils;
 import org.springframework.http.HttpHeaders;
@@ -40,7 +41,6 @@ import org.springframework.http.InvalidMediaTypeException;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.ServerHttpRequest;
 import org.springframework.http.server.ServerHttpResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -342,8 +342,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 	 * @since 4.1.2
 	 */
 	@SuppressWarnings("ConstantConditions")
-	@Nullable
-	public Collection<String> getAllowedOrigins() {
+	public @Nullable Collection<String> getAllowedOrigins() {
 		return this.corsConfiguration.getAllowedOrigins();
 	}
 	/**
@@ -365,8 +364,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 	 * @since 5.3.2
 	 */
 	@SuppressWarnings("ConstantConditions")
-	@Nullable
-	public Collection<String> getAllowedOriginPatterns() {
+	public @Nullable Collection<String> getAllowedOriginPatterns() {
 		return this.corsConfiguration.getAllowedOriginPatterns();
 	}
 
@@ -542,8 +540,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 	}
 
 	@Override
-	@Nullable
-	public CorsConfiguration getCorsConfiguration(HttpServletRequest request) {
+	public @Nullable CorsConfiguration getCorsConfiguration(HttpServletRequest request) {
 		if (!this.suppressCors && (request.getHeader(HttpHeaders.ORIGIN) != null)) {
 			return this.corsConfiguration;
 		}