Refine null-safety in spring-webflux

See spring-projectsgh-32475

spring-webflux/src/main/java/org/springframework/web/reactive/config/DelegatingWebFluxConfiguration.java

@@ -22,6 +22,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 import org.springframework.validation.MessageCodesResolver;
 import org.springframework.validation.Validator;
@@ -63,12 +64,14 @@ protected void addFormatters(FormatterRegistry registry) {
 	}
 
 	@Override
+	@Nullable
 	protected Validator getValidator() {
 		Validator validator = this.configurers.getValidator();
 		return (validator != null ? validator : super.getValidator());
 	}
 
 	@Override
+	@Nullable
 	protected MessageCodesResolver getMessageCodesResolver() {
 		MessageCodesResolver messageCodesResolver = this.configurers.getMessageCodesResolver();
 		return (messageCodesResolver != null ? messageCodesResolver : super.getMessageCodesResolver());
@@ -110,6 +113,7 @@ protected void configureViewResolvers(ViewResolverRegistry registry) {
 	}
 
 	@Override
+	@Nullable
 	protected WebSocketService getWebSocketService() {
 		WebSocketService service = this.configurers.getWebSocketService();
 		return (service != null ? service : super.getWebSocketService());

spring-webflux/src/main/java/org/springframework/web/reactive/config/WebFluxConfigurerComposite.java

@@ -61,11 +61,13 @@ public void addFormatters(FormatterRegistry registry) {
 	}
 
 	@Override
+	@Nullable
 	public Validator getValidator() {
 		return createSingleBean(WebFluxConfigurer::getValidator, Validator.class);
 	}
 
 	@Override
+	@Nullable
 	public MessageCodesResolver getMessageCodesResolver() {
 		return createSingleBean(WebFluxConfigurer::getMessageCodesResolver, MessageCodesResolver.class);
 	}

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultClientRequestBuilder.java

@@ -242,6 +242,7 @@ public Map<String, Object> attributes() {
 		}
 
 		@Override
+		@Nullable
 		public Consumer<ClientHttpRequest> httpRequest() {
 			return this.httpRequestConsumer;
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClientException.java

@@ -17,6 +17,7 @@
 package org.springframework.web.reactive.function.client;
 
 import org.springframework.core.NestedRuntimeException;
+import org.springframework.lang.Nullable;
 
 /**
  * Abstract base class for exception published by {@link WebClient} in case of errors.
@@ -42,7 +43,7 @@ public WebClientException(String msg) {
 	 * @param msg the message
 	 * @param ex the exception
 	 */
-	public WebClientException(String msg, Throwable ex) {
+	public WebClientException(@Nullable String msg, Throwable ex) {
 		super(msg, ex);
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/support/ServerRequestWrapper.java

@@ -41,6 +41,7 @@
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.RequestPath;
 import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.WebDataBinder;
@@ -283,6 +284,7 @@ public Optional<MediaType> contentType() {
 		}
 
 		@Override
+		@Nullable
 		public InetSocketAddress host() {
 			return this.headers.host();
 		}

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

@@ -186,7 +186,7 @@ protected Object lookupHandler(PathContainer lookupPath, ServerWebExchange excha
 	 * @param exchange current exchange
 	 */
 	@SuppressWarnings("UnusedParameters")
-	protected void validateHandler(Object handler, ServerWebExchange exchange) {
+	protected void validateHandler(@Nullable Object handler, ServerWebExchange exchange) {
 	}
 
 	/**

spring-webflux/src/main/java/org/springframework/web/reactive/resource/AbstractFileNameVersionStrategy.java

@@ -22,6 +22,7 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -40,6 +41,7 @@ public abstract class AbstractFileNameVersionStrategy implements VersionStrategy
 
 
 	@Override
+	@Nullable
 	public String extractVersion(String requestPath) {
 		Matcher matcher = pattern.matcher(requestPath);
 		if (matcher.find()) {

spring-webflux/src/main/java/org/springframework/web/reactive/resource/AbstractPrefixVersionStrategy.java

@@ -19,6 +19,7 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -44,6 +45,7 @@ protected AbstractPrefixVersionStrategy(String version) {
 
 
 	@Override
+	@Nullable
 	public String extractVersion(String requestPath) {
 		return (requestPath.startsWith(this.prefix) ? this.prefix : null);
 	}

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

@@ -400,6 +400,7 @@ protected boolean hasCorsConfigurationSource(Object handler) {
 	}
 
 	@Override
+	@Nullable
 	protected CorsConfiguration getCorsConfiguration(Object handler, ServerWebExchange exchange) {
 		CorsConfiguration corsConfig = super.getCorsConfiguration(handler, exchange);
 		if (handler instanceof HandlerMethod handlerMethod) {

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

@@ -36,6 +36,7 @@
 import org.springframework.http.server.PathContainer;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.observation.ServerRequestObservationContext;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.MultiValueMap;
@@ -87,6 +88,7 @@ protected Set<String> getDirectPaths(RequestMappingInfo info) {
 	 * @return an info in case of a match; or {@code null} otherwise.
 	 */
 	@Override
+	@Nullable
 	protected RequestMappingInfo getMatchingMapping(RequestMappingInfo info, ServerWebExchange exchange) {
 		return info.getMatchingCondition(exchange);
 	}
@@ -171,6 +173,7 @@ protected void handleMatch(RequestMappingInfo info, HandlerMethod handlerMethod,
 	 * method but not by query parameter conditions
 	 */
 	@Override
+	@Nullable
 	protected HandlerMethod handleNoMatch(Set<RequestMappingInfo> infos,
 			ServerWebExchange exchange) throws Exception {
 

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

@@ -65,6 +65,7 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		HttpCookie cookie = exchange.getRequest().getCookies().getFirst(name);
 		Class<?> paramType = parameter.getNestedParameterType();

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

@@ -63,6 +63,7 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		// No name to resolve
 		return null;

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

@@ -85,6 +85,7 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		String attributeName = HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE;
 		return exchange.getAttributeOrDefault(attributeName, Collections.emptyMap()).get(name);

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

@@ -78,6 +78,7 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		List<String> headerValues = exchange.getRequest().getHeaders().get(name);
 		Object result = null;

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

@@ -356,6 +356,7 @@ private void updateConsumesCondition(RequestMappingInfo info, Method method) {
 	}
 
 	@Override
+	@Nullable
 	protected CorsConfiguration initCorsConfiguration(Object handler, Method method, RequestMappingInfo mappingInfo) {
 		HandlerMethod handlerMethod = createHandlerMethod(handler, method);
 		Class<?> beanType = handlerMethod.getBeanType();

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

@@ -98,6 +98,7 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 	}
 
 	@Override
+	@Nullable
 	protected Object resolveNamedValue(String name, MethodParameter parameter, ServerWebExchange exchange) {
 		List<String> paramValues = exchange.getRequest().getQueryParams().get(name);
 		Object result = null;