Missing @Nullable annotations in WebFlux, in particular around locale resolution

Issue: SPR-15036
Issue: SPR-15540

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

@@ -112,11 +112,13 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 		mapping.setCorsConfigurations(getCorsConfigurations());
 
 		PathMatchConfigurer configurer = getPathMatchConfigurer();
-		if (configurer.isUseTrailingSlashMatch() != null) {
-			mapping.setUseTrailingSlashMatch(configurer.isUseTrailingSlashMatch());
+		Boolean useTrailingSlashMatch = configurer.isUseTrailingSlashMatch();
+		Boolean useCaseSensitiveMatch = configurer.isUseCaseSensitiveMatch();
+		if (useTrailingSlashMatch != null) {
+			mapping.setUseTrailingSlashMatch(useTrailingSlashMatch);
 		}
-		if (configurer.isUseCaseSensitiveMatch() != null) {
-			mapping.setUseCaseSensitiveMatch(configurer.isUseCaseSensitiveMatch());
+		if (useCaseSensitiveMatch != null) {
+			mapping.setUseCaseSensitiveMatch(useCaseSensitiveMatch);
 		}
 		return mapping;
 	}
@@ -209,11 +211,13 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 		AbstractHandlerMapping handlerMapping = registry.getHandlerMapping();
 		if (handlerMapping != null) {
 			PathMatchConfigurer configurer = getPathMatchConfigurer();
-			if (configurer.isUseTrailingSlashMatch() != null) {
-				handlerMapping.setUseTrailingSlashMatch(configurer.isUseTrailingSlashMatch());
+			Boolean useTrailingSlashMatch = configurer.isUseTrailingSlashMatch();
+			Boolean useCaseSensitiveMatch = configurer.isUseCaseSensitiveMatch();
+			if (useTrailingSlashMatch != null) {
+				handlerMapping.setUseTrailingSlashMatch(useTrailingSlashMatch);
 			}
-			if (configurer.isUseCaseSensitiveMatch() != null) {
-				handlerMapping.setUseCaseSensitiveMatch(configurer.isUseCaseSensitiveMatch());
+			if (useCaseSensitiveMatch != null) {
+				handlerMapping.setUseCaseSensitiveMatch(useCaseSensitiveMatch);
 			}
 		}
 		else {

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

@@ -27,6 +27,7 @@ import java.util.stream.Stream;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.core.Conventions;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
@@ -155,7 +156,7 @@ class DefaultRenderingResponseBuilder implements RenderingResponse.Builder {
 			ServerHttpResponse response = exchange.getResponse();
 			writeStatusAndHeaders(response);
 			MediaType contentType = exchange.getResponse().getHeaders().getContentType();
-			Locale locale = exchange.getLocaleContext().getLocale();
+			Locale locale = LocaleContextHolder.getLocale(exchange.getLocaleContext());
 			Stream<ViewResolver> viewResolverStream = context.viewResolvers().stream();
 
 			return Flux.fromStream(viewResolverStream)

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

@@ -22,8 +22,10 @@ import org.springframework.web.util.pattern.PathPattern;
 
 /**
  * Result of matching an request lookup path against {@link PathPattern} instances.
- * <p>Each result optionnally associates the matching {@link PathPattern}
+ *
+ * <p>Each result optionally associates the matching {@link PathPattern}
  * with a request handler of type {@code T}.
+ *
  * @author Brian Clozel
  * @since 5.0
  * @see PathPatternRegistry
@@ -34,17 +36,19 @@ public class PathMatchResult<T> {
 
 	private final T handler;
 
-	public PathMatchResult(PathPattern pattern, T handler) {
-		Assert.notNull(pattern, "PathPattern should not be null");
+
+	public PathMatchResult(PathPattern pattern, @Nullable T handler) {
+		Assert.notNull(pattern, "PathPattern must not be null");
 		this.pattern = pattern;
 		this.handler = handler;
 	}
 
+
 	/**
 	 * Return the {@link PathPattern} that matched the incoming request.
 	 */
 	public PathPattern getPattern() {
-		return pattern;
+		return this.pattern;
 	}
 
 	/**
@@ -52,7 +56,7 @@ public class PathMatchResult<T> {
 	 */
 	@Nullable
 	public T getHandler() {
-		return handler;
+		return this.handler;
 	}
 
 }

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

@@ -25,6 +25,7 @@ import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.stream.Collectors;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 import org.springframework.web.util.pattern.PathPattern;
 import org.springframework.web.util.pattern.PathPatternComparator;
@@ -55,7 +56,6 @@ public class PathPatternRegistry<T> {
 	/**
 	 * Create a new {@code PathPatternRegistry} using
 	 * the provided instance of {@link PathPatternParser}.
-	 *
 	 * @param patternParser the {@link PathPatternParser} to use
 	 */
 	public PathPatternRegistry(PathPatternParser patternParser) {
@@ -66,7 +66,6 @@ public class PathPatternRegistry<T> {
 	 * Create a new {@code PathPatternRegistry} using
 	 * the provided instance of {@link PathPatternParser}
 	 * and the given map of {@link PathPattern}.
-	 *
 	 * @param patternParser the {@link PathPatternParser} to use
 	 * @param patternsMap the map of {@link PathPattern} to use
 	 */
@@ -75,6 +74,7 @@ public class PathPatternRegistry<T> {
 		this.patternsMap = new HashMap<>(patternsMap);
 	}
 
+
 	/**
 	 * Return a (read-only) map of all patterns and associated values.
 	 */
@@ -84,7 +84,6 @@ public class PathPatternRegistry<T> {
 
 	/**
 	 * Return a {@code SortedSet} of {@code PathPattern}s matching the given {@code lookupPath}.
-	 *
 	 * <p>The returned set sorted with the most specific
 	 * patterns first, according to the given {@code lookupPath}.
 	 * @param lookupPath the URL lookup path to be matched against
@@ -99,7 +98,6 @@ public class PathPatternRegistry<T> {
 
 	/**
 	 * Return, if any, the most specific {@code PathPattern} matching the given {@code lookupPath}.
-	 *
 	 * @param lookupPath the URL lookup path to be matched against
 	 */
 	public Optional<PathMatchResult<T>> findFirstMatch(String lookupPath) {
@@ -120,7 +118,7 @@ public class PathPatternRegistry<T> {
 	/**
 	 * Parse the given {@code rawPattern} and adds it to this registry.
 	 * @param rawPattern raw path pattern to parse and register
-	 * @param handler
+	 * @param handler the associated handler object
 	 */
 	public void register(String rawPattern, T handler) {
 		String fixedPattern = prependLeadingSlash(rawPattern);
@@ -137,6 +135,7 @@ public class PathPatternRegistry<T> {
 		}
 	}
 
+
 	private class PathMatchResultComparator<T> implements Comparator<PathMatchResult<T>> {
 
 		private final String path;
@@ -146,7 +145,7 @@ public class PathPatternRegistry<T> {
 		}
 
 		@Override
-		public int compare(PathMatchResult<T> o1, PathMatchResult<T> o2) {
+		public int compare(@Nullable PathMatchResult<T> o1, @Nullable PathMatchResult<T> o2) {
 			// Nulls get sorted to the end
 			if (o1 == null) {
 				return (o2 == null ? 0 : +1);
@@ -171,7 +170,6 @@ public class PathPatternRegistry<T> {
 			}
 			return result;
 		}
-
 	}
 
-}
+}

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

@@ -32,12 +32,12 @@ import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.core.annotation.AnnotationAwareOrderComparator;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.lang.Nullable;
+import org.springframework.web.reactive.handler.PathMatchResult;
+import org.springframework.web.reactive.handler.PathPatternRegistry;
 import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
 import org.springframework.web.server.ServerWebExchange;
-import org.springframework.web.reactive.handler.PathMatchResult;
 import org.springframework.web.util.pattern.PathPattern;
 import org.springframework.web.util.pattern.PathPatternParser;
-import org.springframework.web.reactive.handler.PathPatternRegistry;
 
 /**
  * A central component to use to obtain the public URL path that clients should
@@ -205,6 +205,9 @@ public class ResourceUrlProvider implements ApplicationListener<ContextRefreshed
 						logger.trace("Invoking ResourceResolverChain for URL pattern \"" + result.getPattern() + "\"");
 					}
 					ResourceWebHandler handler = result.getHandler();
+					if (handler == null) {
+						throw new IllegalStateException("No handler for URL pattern \"" + result.getPattern() + "\"");
+					}
 					ResourceResolverChain chain = new DefaultResourceResolverChain(handler.getResourceResolvers());
 					return chain.resolveUrlPath(pathWithinMapping, handler.getLocations())
 							.map(resolvedPath -> {

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/ViewResolutionResultHandler.java

@@ -29,6 +29,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.core.Conventions;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.Ordered;
@@ -200,8 +201,7 @@ public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
 					Mono<List<View>> viewsMono;
 					Model model = result.getModel();
 					MethodParameter parameter = result.getReturnTypeSource();
-
-					Locale locale = exchange.getLocaleContext().getLocale();
+					Locale locale = LocaleContextHolder.getLocale(exchange.getLocaleContext());
 
 					Class<?> clazz = valueType.getRawClass();
 					if (clazz == null) {

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/freemarker/FreeMarkerView.java

@@ -39,6 +39,7 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.context.ApplicationContextException;
+import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
@@ -188,8 +189,7 @@ public class FreeMarkerView extends AbstractUrlBasedView {
 			logger.debug("Rendering FreeMarker template [" + getUrl() + "].");
 		}
 
-		Locale locale = exchange.getLocaleContext().getLocale();
-
+		Locale locale = LocaleContextHolder.getLocale(exchange.getLocaleContext());
 		DataBuffer dataBuffer = exchange.getResponse().bufferFactory().allocateBuffer();
 		try {
 			Charset charset = getCharset(contentType);