Refine null-safety in spring-web and spring-websocket

See gh-32475

spring-web/src/main/java/org/springframework/web/DefaultErrorResponseBuilder.java

@@ -211,6 +211,7 @@ final class DefaultErrorResponseBuilder implements ErrorResponse.Builder {
 		}
 
 		@Override
+		@Nullable
 		public Object[] getDetailMessageArguments() {
 			return this.detailMessageArguments;
 		}

spring-web/src/main/java/org/springframework/web/ErrorResponseException.java

@@ -165,6 +165,7 @@ public class ErrorResponseException extends NestedRuntimeException implements Er
 	}
 
 	@Override
+	@Nullable
 	public Object[] getDetailMessageArguments() {
 		return this.messageDetailArguments;
 	}

spring-web/src/main/java/org/springframework/web/HttpMediaTypeException.java

@@ -73,7 +73,7 @@ public abstract class HttpMediaTypeException extends ServletException implements
 	 * resolving the problem "detail" through a {@code MessageSource}
 	 * @since 6.0
 	 */
-	protected HttpMediaTypeException(String message, List<MediaType> supportedMediaTypes,
+	protected HttpMediaTypeException(@Nullable String message, List<MediaType> supportedMediaTypes,
 			@Nullable String messageDetailCode, @Nullable Object[] messageDetailArguments) {
 
 		super(message);
@@ -102,6 +102,7 @@ public abstract class HttpMediaTypeException extends ServletException implements
 	}
 
 	@Override
+	@Nullable
 	public Object[] getDetailMessageArguments() {
 		return this.messageDetailArguments;
 	}

spring-web/src/main/java/org/springframework/web/HttpMediaTypeNotSupportedException.java

@@ -63,7 +63,7 @@ public class HttpMediaTypeNotSupportedException extends HttpMediaTypeException {
 	 * @param mediaTypes list of supported media types
 	 * @since 6.0.5
 	 */
-	public HttpMediaTypeNotSupportedException(String message, List<MediaType> mediaTypes) {
+	public HttpMediaTypeNotSupportedException(@Nullable String message, List<MediaType> mediaTypes) {
 		super(message, mediaTypes, PARSE_ERROR_DETAIL_CODE, null);
 		this.contentType = null;
 		this.httpMethod = null;

spring-web/src/main/java/org/springframework/web/accept/ServletPathExtensionContentNegotiationStrategy.java

@@ -99,6 +99,7 @@ public class ServletPathExtensionContentNegotiationStrategy extends PathExtensio
 	 * @since 4.3
 	 */
 	@Override
+	@Nullable
 	public MediaType getMediaTypeForResource(Resource resource) {
 		MediaType mediaType = null;
 		String mimeType = this.servletContext.getMimeType(resource.getFilename());

spring-web/src/main/java/org/springframework/web/bind/ServletRequestBindingException.java

@@ -50,7 +50,7 @@ public class ServletRequestBindingException extends ServletException implements
 	 * Constructor with a message only.
 	 * @param msg the detail message
 	 */
-	public ServletRequestBindingException(String msg) {
+	public ServletRequestBindingException(@Nullable String msg) {
 		this(msg, null, null);
 	}
 
@@ -59,7 +59,7 @@ public class ServletRequestBindingException extends ServletException implements
 	 * @param msg the detail message
 	 * @param cause the root cause
 	 */
-	public ServletRequestBindingException(String msg, Throwable cause) {
+	public ServletRequestBindingException(@Nullable String msg, @Nullable Throwable cause) {
 		this(msg, cause, null, null);
 	}
 
@@ -73,7 +73,7 @@ public class ServletRequestBindingException extends ServletException implements
 	 * @since 6.0
 	 */
 	protected ServletRequestBindingException(
-			String msg, @Nullable String messageDetailCode, @Nullable Object[] messageDetailArguments) {
+			@Nullable String msg, @Nullable String messageDetailCode, @Nullable Object[] messageDetailArguments) {
 
 		this(msg, null, messageDetailCode, messageDetailArguments);
 	}
@@ -88,7 +88,7 @@ public class ServletRequestBindingException extends ServletException implements
 	 * resolving the problem "detail" through a {@code MessageSource}
 	 * @since 6.0
 	 */
-	protected ServletRequestBindingException(String msg, @Nullable Throwable cause,
+	protected ServletRequestBindingException(@Nullable String msg, @Nullable Throwable cause,
 			@Nullable String messageDetailCode, @Nullable Object[] messageDetailArguments) {
 
 		super(msg, cause);
@@ -118,6 +118,7 @@ public class ServletRequestBindingException extends ServletException implements
 	}
 
 	@Override
+	@Nullable
 	public Object[] getDetailMessageArguments() {
 		return this.messageDetailArguments;
 	}

spring-web/src/main/java/org/springframework/web/bind/support/BindParamNameResolver.java

@@ -17,6 +17,7 @@
 package org.springframework.web.bind.support;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.DataBinder;
 import org.springframework.web.bind.annotation.BindParam;
@@ -32,6 +33,7 @@ import org.springframework.web.bind.annotation.BindParam;
 public final class BindParamNameResolver implements DataBinder.NameResolver {
 
 	@Override
+	@Nullable
 	public String resolveName(MethodParameter parameter) {
 		BindParam bindParam = parameter.getParameterAnnotation(BindParam.class);
 		if (bindParam != null) {

spring-web/src/main/java/org/springframework/web/bind/support/WebExchangeDataBinder.java

@@ -162,6 +162,7 @@ public class WebExchangeDataBinder extends WebDataBinder {
 	private record MapValueResolver(Map<String, Object> map) implements ValueResolver {
 
 		@Override
+		@Nullable
 		public Object resolveValue(String name, Class<?> type) {
 			return this.map.get(name);
 		}

spring-web/src/main/java/org/springframework/web/client/HttpMessageConverterExtractor.java

@@ -84,6 +84,7 @@ public class HttpMessageConverterExtractor<T> implements ResponseExtractor<T> {
 
 
 	@Override
+	@Nullable
 	@SuppressWarnings({"rawtypes", "unchecked", "resource"})
 	public T extractData(ClientHttpResponse response) throws IOException {
 		IntrospectingClientHttpResponse responseWrapper = new IntrospectingClientHttpResponse(response);

spring-web/src/main/java/org/springframework/web/client/ResourceAccessException.java

@@ -18,6 +18,8 @@ package org.springframework.web.client;
 
 import java.io.IOException;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Exception thrown when an I/O error occurs.
  *
@@ -42,7 +44,7 @@ public class ResourceAccessException extends RestClientException {
 	 * @param msg the message
 	 * @param ex the {@code IOException}
 	 */
-	public ResourceAccessException(String msg, IOException ex) {
+	public ResourceAccessException(String msg, @Nullable IOException ex) {
 		super(msg, ex);
 	}
 

spring-web/src/main/java/org/springframework/web/client/RestClientException.java

@@ -18,6 +18,7 @@ package org.springframework.web.client;
 
 import org.springframework.core.NestedRuntimeException;
 import org.springframework.http.client.ClientHttpResponse;
+import org.springframework.lang.Nullable;
 
 /**
  * Base class for exceptions thrown by {@link RestTemplate} in case a request
@@ -47,7 +48,7 @@ public class RestClientException extends NestedRuntimeException {
 	 * @param msg the message
 	 * @param ex the exception
 	 */
-	public RestClientException(String msg, Throwable ex) {
+	public RestClientException(String msg, @Nullable Throwable ex) {
 		super(msg, ex);
 	}
 

spring-web/src/main/java/org/springframework/web/client/support/RestClientAdapter.java

@@ -25,6 +25,7 @@ import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.ResponseEntity;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.client.RestClient;
 import org.springframework.web.service.invoker.HttpExchangeAdapter;
@@ -69,6 +70,7 @@ public final class RestClientAdapter implements HttpExchangeAdapter {
 	}
 
 	@Override
+	@Nullable
 	public <T> T exchangeForBody(HttpRequestValues values, ParameterizedTypeReference<T> bodyType) {
 		return newRequest(values).retrieve().body(bodyType);
 	}

spring-web/src/main/java/org/springframework/web/context/request/FacesRequestAttributes.java

@@ -24,6 +24,7 @@ import jakarta.faces.context.FacesContext;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
@@ -102,6 +103,7 @@ public class FacesRequestAttributes implements RequestAttributes {
 
 
 	@Override
+	@Nullable
 	public Object getAttribute(String name, int scope) {
 		return getAttributeMap(scope).get(name);
 	}
@@ -130,6 +132,7 @@ public class FacesRequestAttributes implements RequestAttributes {
 	}
 
 	@Override
+	@Nullable
 	public Object resolveReference(String key) {
 		return switch (key) {
 			case REFERENCE_REQUEST -> getExternalContext().getRequest();

spring-web/src/main/java/org/springframework/web/context/request/FacesWebRequest.java

@@ -58,6 +58,7 @@ public class FacesWebRequest extends FacesRequestAttributes implements NativeWeb
 	}
 
 	@Override
+	@Nullable
 	@SuppressWarnings("unchecked")
 	public <T> T getNativeRequest(@Nullable Class<T> requiredType) {
 		if (requiredType != null) {
@@ -70,6 +71,7 @@ public class FacesWebRequest extends FacesRequestAttributes implements NativeWeb
 	}
 
 	@Override
+	@Nullable
 	@SuppressWarnings("unchecked")
 	public <T> T getNativeResponse(@Nullable Class<T> requiredType) {
 		if (requiredType != null) {

spring-web/src/main/java/org/springframework/web/context/request/ServletRequestAttributes.java

@@ -143,6 +143,7 @@ public class ServletRequestAttributes extends AbstractRequestAttributes {
 
 
 	@Override
+	@Nullable
 	public Object getAttribute(String name, int scope) {
 		if (scope == SCOPE_REQUEST) {
 			if (!isRequestActive()) {
@@ -242,6 +243,7 @@ public class ServletRequestAttributes extends AbstractRequestAttributes {
 	}
 
 	@Override
+	@Nullable
 	public Object resolveReference(String key) {
 		if (REFERENCE_REQUEST.equals(key)) {
 			return this.request;

spring-web/src/main/java/org/springframework/web/context/request/ServletWebRequest.java

@@ -98,16 +98,19 @@ public class ServletWebRequest extends ServletRequestAttributes implements Nativ
 	}
 
 	@Override
+	@Nullable
 	public Object getNativeResponse() {
 		return getResponse();
 	}
 
 	@Override
+	@Nullable
 	public <T> T getNativeRequest(@Nullable Class<T> requiredType) {
 		return WebUtils.getNativeRequest(getRequest(), requiredType);
 	}
 
 	@Override
+	@Nullable
 	public <T> T getNativeResponse(@Nullable Class<T> requiredType) {
 		HttpServletResponse response = getResponse();
 		return (response != null ? WebUtils.getNativeResponse(response, requiredType) : null);

spring-web/src/main/java/org/springframework/web/context/request/async/StandardServletAsyncWebRequest.java

@@ -101,7 +101,7 @@ public class StandardServletAsyncWebRequest extends ServletWebRequest implements
 	 * container processing thread has exited.
 	 */
 	@Override
-	public void setTimeout(Long timeout) {
+	public void setTimeout(@Nullable Long timeout) {
 		Assert.state(!isAsyncStarted(), "Cannot change the timeout with concurrent handling in progress");
 		this.timeout = timeout;
 	}

spring-web/src/main/java/org/springframework/web/context/support/ServletContextAttributeFactoryBean.java

@@ -77,6 +77,7 @@ public class ServletContextAttributeFactoryBean implements FactoryBean<Object>,
 	}
 
 	@Override
+	@Nullable
 	public Class<?> getObjectType() {
 		return (this.attribute != null ? this.attribute.getClass() : null);
 	}

spring-web/src/main/java/org/springframework/web/context/support/StaticWebApplicationContext.java

@@ -139,6 +139,7 @@ public class StaticWebApplicationContext extends StaticApplicationContext
 	}
 
 	@Override
+	@Nullable
 	public String[] getConfigLocations() {
 		return null;
 	}

spring-web/src/main/java/org/springframework/web/cors/DefaultCorsProcessor.java

@@ -155,7 +155,7 @@ public class DefaultCorsProcessor implements CorsProcessor {
 			responseHeaders.setAccessControlAllowMethods(allowMethods);
 		}
 
-		if (preFlightRequest && !allowHeaders.isEmpty()) {
+		if (preFlightRequest && !CollectionUtils.isEmpty(allowHeaders)) {
 			responseHeaders.setAccessControlAllowHeaders(allowHeaders);
 		}
 

spring-web/src/main/java/org/springframework/web/cors/reactive/DefaultCorsProcessor.java

@@ -153,7 +153,7 @@ public class DefaultCorsProcessor implements CorsProcessor {
 			responseHeaders.setAccessControlAllowMethods(allowMethods);
 		}
 
-		if (preFlightRequest && !allowHeaders.isEmpty()) {
+		if (preFlightRequest && !CollectionUtils.isEmpty(allowHeaders)) {
 			responseHeaders.setAccessControlAllowHeaders(allowHeaders);
 		}
 

spring-web/src/main/java/org/springframework/web/filter/ForwardedHeaderFilter.java

@@ -340,6 +340,7 @@ public class ForwardedHeaderFilter extends OncePerRequestFilter {
 
 		@SuppressWarnings("DataFlowIssue")
 		@Override
+		@Nullable
 		public Object getAttribute(String name) {
 			if (name.equals(WebUtils.ERROR_REQUEST_URI_ATTRIBUTE)) {
 				return this.forwardedPrefixExtractor.getErrorRequestUri();

spring-web/src/main/java/org/springframework/web/filter/ServerHttpObservationFilter.java

@@ -139,6 +139,7 @@ public class ServerHttpObservationFilter extends OncePerRequestFilter {
 		return observation;
 	}
 
+	@Nullable
 	private Throwable unwrapServletException(Throwable ex) {
 		return (ex instanceof ServletException) ? ex.getCause() : ex;
 	}

spring-web/src/main/java/org/springframework/web/method/annotation/ExceptionHandlerMethodResolver.java

@@ -174,6 +174,7 @@ public class ExceptionHandlerMethodResolver {
 	 * Return the {@link Method} mapped to the given exception type, or
 	 * {@link #NO_MATCHING_EXCEPTION_HANDLER_METHOD} if none.
 	 */
+	@Nullable
 	private Method getMappedMethod(Class<? extends Throwable> exceptionType) {
 		List<Class<? extends Throwable>> matches = new ArrayList<>();
 		for (Class<? extends Throwable> mappedException : this.mappedMethods.keySet()) {

spring-web/src/main/java/org/springframework/web/method/annotation/MethodArgumentConversionNotSupportedException.java

@@ -37,7 +37,7 @@ public class MethodArgumentConversionNotSupportedException extends ConversionNot
 
 
 	public MethodArgumentConversionNotSupportedException(@Nullable Object value,
-			@Nullable Class<?> requiredType, String name, MethodParameter param, Throwable cause) {
+			@Nullable Class<?> requiredType, String name, MethodParameter param, @Nullable Throwable cause) {
 
 		super(value, requiredType, cause);
 		this.name = name;

spring-web/src/main/java/org/springframework/web/method/annotation/MethodArgumentTypeMismatchException.java

@@ -37,7 +37,7 @@ public class MethodArgumentTypeMismatchException extends TypeMismatchException {
 
 
 	public MethodArgumentTypeMismatchException(@Nullable Object value,
-			@Nullable Class<?> requiredType, String name, MethodParameter param, Throwable cause) {
+			@Nullable Class<?> requiredType, String name, MethodParameter param, @Nullable Throwable cause) {
 
 		super(value, requiredType, cause);
 		this.name = name;

spring-web/src/main/java/org/springframework/web/multipart/MultipartFileResource.java

@@ -65,6 +65,7 @@ class MultipartFileResource extends AbstractResource {
 	}
 
 	@Override
+	@Nullable
 	public String getFilename() {
 		return this.multipartFile.getOriginalFilename();
 	}

spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java

@@ -130,6 +130,7 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 	}
 
 	@Override
+	@Nullable
 	public String getMultipartContentType(String paramOrFileName) {
 		MultipartFile file = getFile(paramOrFileName);
 		if (file != null) {
@@ -141,6 +142,7 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 	}
 
 	@Override
+	@Nullable
 	public HttpHeaders getMultipartHeaders(String paramOrFileName) {
 		String contentType = getMultipartContentType(paramOrFileName);
 		if (contentType != null) {
@@ -167,6 +169,7 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 	 * lazily initializing it if necessary.
 	 * @see #initializeMultipart()
 	 */
+	@SuppressWarnings("NullAway")
 	protected Map<String, String[]> getMultipartParameters() {
 		if (this.multipartParameters == null) {
 			initializeMultipart();
@@ -187,6 +190,7 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 	 * lazily initializing it if necessary.
 	 * @see #initializeMultipart()
 	 */
+	@SuppressWarnings("NullAway")
 	protected Map<String, String> getMultipartParameterContentTypes() {
 		if (this.multipartParameterContentTypes == null) {
 			initializeMultipart();

spring-web/src/main/java/org/springframework/web/multipart/support/StandardMultipartHttpServletRequest.java

@@ -176,6 +176,7 @@ public class StandardMultipartHttpServletRequest extends AbstractMultipartHttpSe
 	}
 
 	@Override
+	@Nullable
 	public String getMultipartContentType(String paramOrFileName) {
 		try {
 			Part part = getPart(paramOrFileName);
@@ -187,6 +188,7 @@ public class StandardMultipartHttpServletRequest extends AbstractMultipartHttpSe
 	}
 
 	@Override
+	@Nullable
 	public HttpHeaders getMultipartHeaders(String paramOrFileName) {
 		try {
 			Part part = getPart(paramOrFileName);

spring-web/src/main/java/org/springframework/web/server/ServerWebExchangeDecorator.java

@@ -94,6 +94,7 @@ public class ServerWebExchangeDecorator implements ServerWebExchange {
 	}
 
 	@Override
+	@Nullable
 	public ApplicationContext getApplicationContext() {
 		return getDelegate().getApplicationContext();
 	}

spring-web/src/main/java/org/springframework/web/service/invoker/CookieValueArgumentResolver.java

@@ -18,6 +18,7 @@ package org.springframework.web.service.invoker;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.CookieValue;
 
 /**
@@ -56,6 +57,7 @@ public class CookieValueArgumentResolver extends AbstractNamedValueArgumentResol
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		CookieValue annot = parameter.getParameterAnnotation(CookieValue.class);
 		return (annot == null ? null :

spring-web/src/main/java/org/springframework/web/service/invoker/HttpRequestValues.java

@@ -408,7 +408,7 @@ public class HttpRequestValues {
 		/**
 		 * Set the request body as an Object to be serialized.
 		 */
-		public void setBodyValue(Object bodyValue) {
+		public void setBodyValue(@Nullable Object bodyValue) {
 			this.bodyValue = bodyValue;
 		}
 

spring-web/src/main/java/org/springframework/web/service/invoker/HttpServiceProxyFactory.java

@@ -294,6 +294,7 @@ public final class HttpServiceProxyFactory {
 		}
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation invocation) throws Throwable {
 			Method method = invocation.getMethod();
 			HttpServiceMethod httpServiceMethod = this.httpServiceMethods.get(method);

spring-web/src/main/java/org/springframework/web/service/invoker/PathVariableArgumentResolver.java

@@ -18,6 +18,7 @@ package org.springframework.web.service.invoker;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.PathVariable;
 
 /**
@@ -48,6 +49,7 @@ public class PathVariableArgumentResolver extends AbstractNamedValueArgumentReso
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		PathVariable annot = parameter.getParameterAnnotation(PathVariable.class);
 		return (annot == null ? null :

spring-web/src/main/java/org/springframework/web/service/invoker/ReactiveHttpRequestValues.java

@@ -221,7 +221,7 @@ public final class ReactiveHttpRequestValues extends HttpRequestValues {
 		 * {@linkplain #setBodyPublisher(Publisher, ParameterizedTypeReference)}.
 		 */
 		@Override
-		public void setBodyValue(Object bodyValue) {
+		public void setBodyValue(@Nullable Object bodyValue) {
 			super.setBodyValue(bodyValue);
 			this.body = null;
 			this.bodyElementType = null;

spring-web/src/main/java/org/springframework/web/service/invoker/RequestAttributeArgumentResolver.java

@@ -17,6 +17,7 @@
 package org.springframework.web.service.invoker;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.RequestAttribute;
 
 /**
@@ -40,6 +41,7 @@ public class RequestAttributeArgumentResolver extends AbstractNamedValueArgument
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		RequestAttribute annot = parameter.getParameterAnnotation(RequestAttribute.class);
 		return (annot == null ? null :

spring-web/src/main/java/org/springframework/web/service/invoker/RequestHeaderArgumentResolver.java

@@ -18,6 +18,7 @@ package org.springframework.web.service.invoker;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.RequestHeader;
 
 /**
@@ -57,6 +58,7 @@ public class RequestHeaderArgumentResolver extends AbstractNamedValueArgumentRes
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		RequestHeader annot = parameter.getParameterAnnotation(RequestHeader.class);
 		return (annot == null ? null :

spring-web/src/main/java/org/springframework/web/service/invoker/RequestParamArgumentResolver.java

@@ -18,6 +18,7 @@ package org.springframework.web.service.invoker;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.RequestParam;
 
 /**
@@ -60,6 +61,7 @@ public class RequestParamArgumentResolver extends AbstractNamedValueArgumentReso
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		RequestParam annot = parameter.getParameterAnnotation(RequestParam.class);
 		return (annot == null ? null :

spring-web/src/main/java/org/springframework/web/service/invoker/RequestPartArgumentResolver.java

@@ -78,6 +78,7 @@ public class RequestPartArgumentResolver extends AbstractNamedValueArgumentResol
 
 
 	@Override
+	@Nullable
 	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 		RequestPart annot = parameter.getParameterAnnotation(RequestPart.class);
 		boolean isMultiPartFile = parameter.nestedIfOptional().getNestedParameterType().equals(MultipartFile.class);

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -1077,6 +1077,7 @@ final class HierarchicalUriComponents extends UriComponents {
 		}
 
 		@Override
+		@Nullable
 		public Object getValue(@Nullable String name) {
 			Object value = this.delegate.getValue(name);
 			if (ObjectUtils.isArray(value)) {

spring-web/src/main/java/org/springframework/web/util/UriComponentsBuilder.java

@@ -676,7 +676,7 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 	}
 
 	@Override
-	public UriComponentsBuilder queryParam(String name, Object... values) {
+	public UriComponentsBuilder queryParam(String name, @Nullable Object... values) {
 		Assert.notNull(name, "Name must not be null");
 		if (!ObjectUtils.isEmpty(values)) {
 			for (Object value : values) {
@@ -926,6 +926,7 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 		}
 
 		@Override
+		@Nullable
 		public PathComponent build() {
 			if (this.path.length() == 0) {
 				return null;
@@ -976,6 +977,7 @@ public class UriComponentsBuilder implements UriBuilder, Cloneable {
 		}
 
 		@Override
+		@Nullable
 		public PathComponent build() {
 			return (this.pathSegments.isEmpty() ? null :
 					new HierarchicalUriComponents.PathSegmentComponent(this.pathSegments));

spring-web/src/main/java/org/springframework/web/util/WebUtils.java

@@ -540,7 +540,7 @@ public abstract class WebUtils {
 	 * @param name the name of the attribute
 	 * @param value the suggested value of the attribute
 	 */
-	private static void exposeRequestAttributeIfNotPresent(ServletRequest request, String name, Object value) {
+	private static void exposeRequestAttributeIfNotPresent(ServletRequest request, String name, @Nullable Object value) {
 		if (request.getAttribute(name) == null) {
 			request.setAttribute(name, value);
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/handler/WebFluxResponseStatusExceptionHandler.java

@@ -18,6 +18,7 @@ package org.springframework.web.reactive.handler;
 
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.http.HttpStatusCode;
+import org.springframework.lang.Nullable;
 import org.springframework.web.bind.annotation.ResponseStatus;
 import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
 
@@ -38,6 +39,7 @@ import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
 public class WebFluxResponseStatusExceptionHandler extends ResponseStatusExceptionHandler {
 
 	@Override
+	@Nullable
 	protected HttpStatusCode determineStatus(Throwable ex) {
 		HttpStatusCode statusCode = super.determineStatus(ex);
 		if (statusCode == null) {

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/RequestAttributeMethodArgumentResolver.java

@@ -66,6 +66,7 @@ public class RequestAttributeMethodArgumentResolver extends AbstractNamedValueSy
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		Object value = exchange.getAttribute(name);
 		ReactiveAdapter toAdapter = getAdapterRegistry().getAdapter(parameter.getParameterType());

spring-webmvc/src/main/java/org/springframework/web/servlet/FrameworkServlet.java

@@ -1215,7 +1215,7 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 			}
 		}
 		@Override
-		public <T> void postProcess(NativeWebRequest webRequest, Callable<T> task, Object concurrentResult) {
+		public <T> void postProcess(NativeWebRequest webRequest, Callable<T> task, @Nullable Object concurrentResult) {
 			HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
 			if (request != null) {
 				resetContextHolders(request, null, null);

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ServletModelAttributeMethodProcessor.java

@@ -70,6 +70,7 @@ public class ServletModelAttributeMethodProcessor extends ModelAttributeMethodPr
 	 * @see #createAttributeFromRequestValue
 	 */
 	@Override
+	@Nullable
 	protected final Object createAttribute(String attributeName, MethodParameter parameter,
 			WebDataBinderFactory binderFactory, NativeWebRequest request) throws Exception {
 

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

@@ -257,6 +257,7 @@ public class WebSocketHttpHeaders extends HttpHeaders {
 	}
 
 	@Override
+	@Nullable
 	public List<String> get(Object key) {
 		return this.headers.get(key);
 	}

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

@@ -114,6 +114,7 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 	}
 
 	@Override
+	@Nullable
 	public String getAcceptedProtocol() {
 		checkNativeSessionInitialized();
 		return this.acceptedProtocol;
@@ -126,6 +127,7 @@ public class JettyWebSocketSession extends AbstractWebSocketSession<Session> {
 	}
 
 	@Override
+	@Nullable
 	public Principal getPrincipal() {
 		return this.user;
 	}

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

@@ -129,6 +129,7 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 	}
 
 	@Override
+	@Nullable
 	public String getAcceptedProtocol() {
 		checkNativeSessionInitialized();
 		return this.acceptedProtocol;
@@ -141,6 +142,7 @@ public class StandardWebSocketSession extends AbstractWebSocketSession<Session>
 	}
 
 	@Override
+	@Nullable
 	public Principal getPrincipal() {
 		return this.user;
 	}

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

@@ -21,6 +21,7 @@ import java.util.List;
 
 import jakarta.websocket.Extension;
 
+import org.springframework.lang.Nullable;
 import org.springframework.web.socket.WebSocketExtension;
 
 /**
@@ -46,6 +47,7 @@ public class WebSocketToStandardExtensionAdapter implements Extension {
 					return paramName;
 				}
 				@Override
+				@Nullable
 				public String getValue() {
 					return extension.getParameters().get(paramName);
 				}

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

@@ -133,6 +133,7 @@ class MessageBrokerBeanDefinitionParser implements BeanDefinitionParser {
 
 
 	@Override
+	@Nullable
 	public BeanDefinition parse(Element element, ParserContext context) {
 		Object source = context.extractSource(element);
 		CompositeComponentDefinition compDefinition = new CompositeComponentDefinition(element.getTagName(), source);

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

@@ -96,21 +96,25 @@ public class WebSocketSessionDecorator implements WebSocketSession {
 	}
 
 	@Override
+	@Nullable
 	public Principal getPrincipal() {
 		return this.delegate.getPrincipal();
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getLocalAddress() {
 		return this.delegate.getLocalAddress();
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getRemoteAddress() {
 		return this.delegate.getRemoteAddress();
 	}
 
 	@Override
+	@Nullable
 	public String getAcceptedProtocol() {
 		return this.delegate.getAcceptedProtocol();
 	}

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

@@ -110,6 +110,7 @@ public abstract class AbstractClientSockJsSession implements WebSocketSession {
 	}
 
 	@Override
+	@Nullable
 	public Principal getPrincipal() {
 		return this.request.getUser();
 	}

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

@@ -207,6 +207,7 @@ public class RestTemplateXhrTransport extends AbstractXhrTransport {
 		}
 
 		@Override
+		@Nullable
 		public Object extractData(ClientHttpResponse response) throws IOException {
 			HttpStatusCode httpStatus = response.getStatusCode();
 			if (httpStatus != HttpStatus.OK) {

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

@@ -74,18 +74,21 @@ public class WebSocketClientSockJsSession extends AbstractClientSockJsSession im
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getLocalAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getLocalAddress();
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getRemoteAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getRemoteAddress();
 	}
 
 	@Override
+	@Nullable
 	public 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

@@ -24,6 +24,7 @@ import java.util.concurrent.CompletableFuture;
 
 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;
@@ -96,17 +97,20 @@ public class XhrClientSockJsSession extends AbstractClientSockJsSession {
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getLocalAddress() {
 		return null;
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getRemoteAddress() {
 		URI uri = getUri();
 		return (uri != null ? new InetSocketAddress(uri.getHost(), uri.getPort()) : null);
 	}
 
 	@Override
+	@Nullable
 	public String getAcceptedProtocol() {
 		return null;
 	}

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

@@ -341,6 +341,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 	 * @since 4.1.2
 	 */
 	@SuppressWarnings("ConstantConditions")
+	@Nullable
 	public Collection<String> getAllowedOrigins() {
 		return this.corsConfiguration.getAllowedOrigins();
 	}
@@ -363,6 +364,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 	 * @since 5.3.2
 	 */
 	@SuppressWarnings("ConstantConditions")
+	@Nullable
 	public Collection<String> getAllowedOriginPatterns() {
 		return this.corsConfiguration.getAllowedOriginPatterns();
 	}
@@ -415,8 +417,8 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 			}
 
 			else if (sockJsPath.matches("/iframe[0-9-.a-z_]*.html")) {
-				if (!getAllowedOrigins().isEmpty() && !getAllowedOrigins().contains("*") ||
-						!getAllowedOriginPatterns().isEmpty()) {
+				if (!CollectionUtils.isEmpty(getAllowedOrigins()) && !getAllowedOrigins().contains("*") ||
+						!CollectionUtils.isEmpty(getAllowedOriginPatterns())) {
 					if (requestInfo != null) {
 						logger.debug("Iframe support is disabled when an origin check is required. " +
 								"Ignoring transport request: " + requestInfo);
@@ -424,7 +426,7 @@ public abstract class AbstractSockJsService implements SockJsService, CorsConfig
 					response.setStatusCode(HttpStatus.NOT_FOUND);
 					return;
 				}
-				if (getAllowedOrigins().isEmpty()) {
+				if (CollectionUtils.isEmpty(getAllowedOrigins())) {
 					response.getHeaders().add(XFRAME_OPTIONS_HEADER, "SAMEORIGIN");
 				}
 				if (requestInfo != null) {

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

@@ -346,8 +346,8 @@ public class TransportHandlingSockJsService extends AbstractSockJsService implem
 			return false;
 		}
 
-		if (!getAllowedOrigins().isEmpty() && !getAllowedOrigins().contains("*") ||
-				!getAllowedOriginPatterns().isEmpty()) {
+		if (!CollectionUtils.isEmpty(getAllowedOrigins()) && !getAllowedOrigins().contains("*") ||
+				!CollectionUtils.isEmpty(getAllowedOriginPatterns())) {
 			TransportType transportType = TransportType.fromValue(transport);
 			if (transportType == null || !transportType.supportsOrigin()) {
 				if (logger.isWarnEnabled()) {

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/WebSocketServerSockJsSession.java

@@ -83,24 +83,28 @@ public class WebSocketServerSockJsSession extends AbstractSockJsSession implemen
 	}
 
 	@Override
+	@Nullable
 	public Principal getPrincipal() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getPrincipal();
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getLocalAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getLocalAddress();
 	}
 
 	@Override
+	@Nullable
 	public InetSocketAddress getRemoteAddress() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getRemoteAddress();
 	}
 
 	@Override
+	@Nullable
 	public String getAcceptedProtocol() {
 		Assert.state(this.webSocketSession != null, "WebSocketSession not yet initialized");
 		return this.webSocketSession.getAcceptedProtocol();