@Nullable all the way: null-safety at field level

This commits extends nullability declarations to the field level, formalizing the interaction between methods and their underlying fields and therefore avoiding any nullability mismatch.

Issue: SPR-15720

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

@@ -37,6 +37,7 @@ import org.springframework.web.server.ServerWebExchange;
  */
 public class BindingContext {
 
+	@Nullable
 	private final WebBindingInitializer initializer;
 
 	private final Model model = new BindingAwareConcurrentModel();

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

@@ -36,12 +36,14 @@ public class HandlerResult {
 
 	private final Object handler;
 
+	@Nullable
 	private final Object returnValue;
 
 	private final ResolvableType returnType;
 
 	private final BindingContext bindingContext;
 
+	@Nullable
 	private Function<Throwable, Mono<HandlerResult>> exceptionHandler;
 
 
@@ -144,7 +146,7 @@ public class HandlerResult {
 	 * @return the new result or the same error if there is no exception handler
 	 */
 	public Mono<HandlerResult> applyExceptionHandler(Throwable failure) {
-		return (hasExceptionHandler() ? this.exceptionHandler.apply(failure) : Mono.error(failure));
+		return (this.exceptionHandler != null ? this.exceptionHandler.apply(failure) : Mono.error(failure));
 	}
 
 }

spring-webflux/src/main/java/org/springframework/web/reactive/accept/RequestedContentTypeResolverBuilder.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.accept;
 
 import java.util.ArrayList;
@@ -25,7 +26,7 @@ import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 import org.springframework.http.MediaType;
-
+import org.springframework.lang.Nullable;
 
 /**
  * Builder for a composite {@link RequestedContentTypeResolver} that delegates
@@ -113,9 +114,9 @@ public class RequestedContentTypeResolverBuilder {
 
 		private final Map<String, MediaType> mediaTypes = new HashMap<>();
 
+		@Nullable
 		private String parameterName;
 
-
 		/**
 		 * Configure a mapping between a lookup key (extracted from a query
 		 * parameter value) and a corresponding {@code MediaType}.

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

@@ -23,6 +23,7 @@ import org.springframework.cache.Cache;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.http.CacheControl;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.resource.ResourceWebHandler;
 
@@ -40,8 +41,10 @@ public class ResourceHandlerRegistration {
 
 	private final List<Resource> locations = new ArrayList<>();
 
+	@Nullable
 	private CacheControl cacheControl;
 
+	@Nullable
 	private ResourceChainRegistration resourceChainRegistration;
 
 
@@ -52,7 +55,8 @@ public class ResourceHandlerRegistration {
 	 * @param pathPatterns one or more resource URL path patterns
 	 */
 	public ResourceHandlerRegistration(ResourceLoader resourceLoader, String... pathPatterns) {
-		Assert.notEmpty(pathPatterns, "At least one path pattern is required for resource handling.");
+		Assert.notNull(resourceLoader, "ResourceLoader is required");
+		Assert.notEmpty(pathPatterns, "At least one path pattern is required for resource handling");
 		this.resourceLoader = resourceLoader;
 		this.pathPatterns = pathPatterns;
 	}
@@ -74,7 +78,7 @@ public class ResourceHandlerRegistration {
 	 */
 	public ResourceHandlerRegistration addResourceLocations(String... resourceLocations) {
 		for (String location : resourceLocations) {
-			this.locations.add(resourceLoader.getResource(location));
+			this.locations.add(this.resourceLoader.getResource(location));
 		}
 		return this;
 	}
@@ -82,7 +86,6 @@ public class ResourceHandlerRegistration {
 	/**
 	 * Specify the {@link CacheControl} which should be used
 	 * by the resource handler.
-	 *
 	 * @param cacheControl the CacheControl configuration to use
 	 * @return the same {@link ResourceHandlerRegistration} instance, for
 	 * chained method invocation
@@ -95,11 +98,9 @@ public class ResourceHandlerRegistration {
 	/**
 	 * Configure a chain of resource resolvers and transformers to use. This
 	 * can be useful, for example, to apply a version strategy to resource URLs.
-	 *
 	 * <p>If this method is not invoked, by default only a simple
 	 * {@code PathResourceResolver} is used in order to match URL paths to
 	 * resources under the configured locations.
-	 *
 	 * @param cacheResources whether to cache the result of resource resolution;
 	 * setting this to "true" is recommended for production (and "false" for
 	 * development, especially when applying a version strategy)
@@ -114,11 +115,9 @@ public class ResourceHandlerRegistration {
 	/**
 	 * Configure a chain of resource resolvers and transformers to use. This
 	 * can be useful, for example, to apply a version strategy to resource URLs.
-	 *
 	 * <p>If this method is not invoked, by default only a simple
 	 * {@code PathResourceResolver} is used in order to match URL paths to
 	 * resources under the configured locations.
-	 *
 	 * @param cacheResources whether to cache the result of resource resolution;
 	 * setting this to "true" is recommended for production (and "false" for
 	 * development, especially when applying a version strategy

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

@@ -23,9 +23,8 @@ import java.util.List;
 import java.util.Map;
 
 import org.springframework.beans.factory.BeanInitializationException;
-import org.springframework.context.ApplicationContext;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
 import org.springframework.web.reactive.handler.AbstractUrlHandlerMapping;
 import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
 import org.springframework.web.reactive.resource.ResourceWebHandler;
@@ -53,7 +52,7 @@ import org.springframework.web.server.WebHandler;
  */
 public class ResourceHandlerRegistry {
 
-	private final ApplicationContext applicationContext;
+	private final ResourceLoader resourceLoader;
 
 	private final List<ResourceHandlerRegistration> registrations = new ArrayList<>();
 
@@ -61,13 +60,12 @@ public class ResourceHandlerRegistry {
 
 
 	/**
-	 * Create a new resource handler registry for the given application context.
-	 * @param applicationContext the Spring application context
+	 * Create a new resource handler registry for the given resource loader
+	 * (typically an application context).
+	 * @param resourceLoader the resource loader to use
 	 */
-	public ResourceHandlerRegistry(ApplicationContext applicationContext) {
-
-		Assert.notNull(applicationContext, "ApplicationContext is required");
-		this.applicationContext = applicationContext;
+	public ResourceHandlerRegistry(ResourceLoader resourceLoader) {
+		this.resourceLoader = resourceLoader;
 	}
 
 
@@ -82,8 +80,7 @@ public class ResourceHandlerRegistry {
 	 * configure the registered resource handler
 	 */
 	public ResourceHandlerRegistration addResourceHandler(String... patterns) {
-		ResourceHandlerRegistration registration =
-				new ResourceHandlerRegistration(this.applicationContext, patterns);
+		ResourceHandlerRegistration registration = new ResourceHandlerRegistration(this.resourceLoader, patterns);
 		this.registrations.add(registration);
 		return registration;
 	}
@@ -126,7 +123,7 @@ public class ResourceHandlerRegistry {
 				try {
 					handler.afterPropertiesSet();
 				}
-				catch (Exception ex) {
+				catch (Throwable ex) {
 					throw new BeanInitializationException("Failed to init ResourceHttpRequestHandler", ex);
 				}
 				urlMap.put(pathPattern, handler);

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

@@ -24,7 +24,7 @@ import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.BeanInitializationException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.Ordered;
-import org.springframework.util.Assert;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 import org.springframework.web.reactive.result.view.HttpMessageWriterView;
 import org.springframework.web.reactive.result.view.UrlBasedViewResolver;
@@ -46,17 +46,18 @@ import org.springframework.web.reactive.result.view.freemarker.FreeMarkerViewRes
  */
 public class ViewResolverRegistry {
 
+	@Nullable
 	private final ApplicationContext applicationContext;
 
 	private final List<ViewResolver> viewResolvers = new ArrayList<>(4);
 
 	private final List<View> defaultViews = new ArrayList<>(4);
 
+	@Nullable
 	private Integer order;
 
 
-	public ViewResolverRegistry(ApplicationContext applicationContext) {
-		Assert.notNull(applicationContext, "ApplicationContext must not be null");
+	public ViewResolverRegistry(@Nullable ApplicationContext applicationContext) {
 		this.applicationContext = applicationContext;
 	}
 
@@ -67,7 +68,7 @@ public class ViewResolverRegistry {
 	 * adding a {@link FreeMarkerConfigurer} bean.
 	 */
 	public UrlBasedViewResolverRegistration freeMarker() {
-		if (this.applicationContext != null && !hasBeanOfType(FreeMarkerConfigurer.class)) {
+		if (!checkBeanOfType(FreeMarkerConfigurer.class)) {
 			throw new BeanInitializationException("In addition to a FreeMarker view resolver " +
 					"there must also be a single FreeMarkerConfig bean in this web application context " +
 					"(or its parent): FreeMarkerConfigurer is the usual implementation. " +
@@ -82,11 +83,6 @@ public class ViewResolverRegistry {
 		return registration;
 	}
 
-	protected boolean hasBeanOfType(Class<?> beanType) {
-		return !ObjectUtils.isEmpty(BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
-				this.applicationContext, beanType, false, false));
-	}
-
 	/**
 	 * Register a {@link ViewResolver} bean instance. This may be useful to
 	 * configure a 3rd party resolver implementation or as an alternative to
@@ -126,6 +122,13 @@ public class ViewResolverRegistry {
 		this.order = order;
 	}
 
+
+	private boolean checkBeanOfType(Class<?> beanType) {
+		return (this.applicationContext == null ||
+				!ObjectUtils.isEmpty(BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
+						this.applicationContext, beanType, false, false)));
+	}
+
 	protected int getOrder() {
 		return (this.order != null ? this.order : Ordered.LOWEST_PRECEDENCE);
 	}

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

@@ -29,6 +29,8 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.annotation.Order;
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.format.Formatter;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.format.support.DefaultFormattingConversionService;
@@ -58,11 +60,11 @@ import org.springframework.web.reactive.result.method.annotation.ResponseBodyRes
 import org.springframework.web.reactive.result.method.annotation.ResponseEntityResultHandler;
 import org.springframework.web.reactive.result.view.ViewResolutionResultHandler;
 import org.springframework.web.reactive.result.view.ViewResolver;
-import org.springframework.web.server.i18n.LocaleContextResolver;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebExceptionHandler;
 import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
 import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
+import org.springframework.web.server.i18n.LocaleContextResolver;
 
 /**
  * The main class for Spring WebFlux configuration.
@@ -74,12 +76,16 @@ import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
  */
 public class WebFluxConfigurationSupport implements ApplicationContextAware {
 
+	@Nullable
 	private Map<String, CorsConfiguration> corsConfigurations;
 
+	@Nullable
 	private PathMatchConfigurer pathMatchConfigurer;
 
+	@Nullable
 	private ViewResolverRegistry viewResolverRegistry;
 
+	@Nullable
 	private ApplicationContext applicationContext;
 
 
@@ -88,7 +94,8 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 		this.applicationContext = applicationContext;
 	}
 
-	protected ApplicationContext getApplicationContext() {
+	@Nullable
+	public final ApplicationContext getApplicationContext() {
 		return this.applicationContext;
 	}
 
@@ -205,7 +212,11 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 	 */
 	@Bean
 	public HandlerMapping resourceHandlerMapping() {
-		ResourceHandlerRegistry registry = new ResourceHandlerRegistry(this.applicationContext);
+		ResourceLoader resourceLoader = this.applicationContext;
+		if (resourceLoader == null) {
+			resourceLoader = new DefaultResourceLoader();
+		}
+		ResourceHandlerRegistry registry = new ResourceHandlerRegistry(resourceLoader);
 		addResourceHandlers(registry);
 
 		AbstractHandlerMapping handlerMapping = registry.getHandlerMapping();
@@ -427,7 +438,7 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 	 */
 	protected final ViewResolverRegistry getViewResolverRegistry() {
 		if (this.viewResolverRegistry == null) {
-			this.viewResolverRegistry = new ViewResolverRegistry(getApplicationContext());
+			this.viewResolverRegistry = new ViewResolverRegistry(this.applicationContext);
 			configureViewResolvers(this.viewResolverRegistry);
 		}
 		return this.viewResolverRegistry;

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

@@ -32,6 +32,7 @@ import org.springframework.lang.Nullable;
 @SuppressWarnings("serial")
 public class UnsupportedMediaTypeException extends NestedRuntimeException {
 
+	@Nullable
 	private final MediaType contentType;
 
 	private final List<MediaType> supportedMediaTypes;

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

@@ -63,8 +63,10 @@ class DefaultWebClient implements WebClient {
 
 	private final UriBuilderFactory uriBuilderFactory;
 
+	@Nullable
 	private final HttpHeaders defaultHeaders;
 
+	@Nullable
 	private final MultiValueMap<String, String> defaultCookies;
 
 	private final DefaultWebClientBuilder builder;
@@ -170,10 +172,13 @@ class DefaultWebClient implements WebClient {
 
 		private final URI uri;
 
+		@Nullable
 		private HttpHeaders headers;
 
+		@Nullable
 		private MultiValueMap<String, String> cookies;
 
+		@Nullable
 		private BodyInserter<?, ? super ClientHttpRequest> inserter;
 
 		DefaultRequestBodySpec(HttpMethod httpMethod, URI uri) {
@@ -284,11 +289,9 @@ class DefaultWebClient implements WebClient {
 
 		@Override
 		public Mono<ClientResponse> exchange() {
-
-			ClientRequest request = this.inserter != null ?
+			ClientRequest request = (this.inserter != null ?
 					initRequestBuilder().body(this.inserter).build() :
-					initRequestBuilder().build();
-
+					initRequestBuilder().build());
 			return exchangeFunction.exchange(request);
 		}
 

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

@@ -42,24 +42,33 @@ import org.springframework.web.util.UriBuilderFactory;
  */
 class DefaultWebClientBuilder implements WebClient.Builder {
 
+	@Nullable
 	private String baseUrl;
 
+	@Nullable
 	private Map<String, ?> defaultUriVariables;
 
+	@Nullable
 	private UriBuilderFactory uriBuilderFactory;
 
+	@Nullable
 	private HttpHeaders defaultHeaders;
 
+	@Nullable
 	private MultiValueMap<String, String> defaultCookies;
 
+	@Nullable
 	private List<ExchangeFilterFunction> filters;
 
+	@Nullable
 	private ClientHttpConnector connector;
 
 	private ExchangeStrategies exchangeStrategies = ExchangeStrategies.withDefaults();
 
+	@Nullable
 	private ExchangeFunction exchangeFunction;
 
+
 	public DefaultWebClientBuilder() {
 	}
 
@@ -85,6 +94,7 @@ class DefaultWebClientBuilder implements WebClient.Builder {
 		this.exchangeFunction = other.exchangeFunction;
 	}
 
+
 	@Override
 	public WebClient.Builder baseUrl(String baseUrl) {
 		this.baseUrl = baseUrl;
@@ -105,9 +115,9 @@ class DefaultWebClientBuilder implements WebClient.Builder {
 
 	@Override
 	public WebClient.Builder defaultHeader(String headerName, String... headerValues) {
-		initHeaders();
+		HttpHeaders headers = initHeaders();
 		for (String headerValue : headerValues) {
-			this.defaultHeaders.add(headerName, headerValue);
+			headers.add(headerName, headerValue);
 		}
 		return this;
 	}
@@ -115,37 +125,35 @@ class DefaultWebClientBuilder implements WebClient.Builder {
 	@Override
 	public WebClient.Builder defaultHeaders(Consumer<HttpHeaders> headersConsumer) {
 		Assert.notNull(headersConsumer, "'headersConsumer' must not be null");
-		initHeaders();
-		headersConsumer.accept(this.defaultHeaders);
+		headersConsumer.accept(initHeaders());
 		return this;
 	}
 
-	private void initHeaders() {
+	private HttpHeaders initHeaders() {
 		if (this.defaultHeaders == null) {
 			this.defaultHeaders = new HttpHeaders();
 		}
+		return this.defaultHeaders;
 	}
 
 	@Override
 	public WebClient.Builder defaultCookie(String cookieName, String... cookieValues) {
-		initCookies();
-		this.defaultCookies.addAll(cookieName, Arrays.asList(cookieValues));
+		initCookies().addAll(cookieName, Arrays.asList(cookieValues));
 		return this;
 	}
 
 	@Override
-	public WebClient.Builder defaultCookies(
-			Consumer<MultiValueMap<String, String>> cookiesConsumer) {
-		Assert.notNull(cookiesConsumer, "'cookiesConsumer' must not be null");
-		initCookies();
-		cookiesConsumer.accept(this.defaultCookies);
+	public WebClient.Builder defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer) {
+		Assert.notNull(cookiesConsumer, "Cookies consumer must not be null");
+		cookiesConsumer.accept(initCookies());
 		return this;
 	}
 
-	private void initCookies() {
+	private MultiValueMap<String, String> initCookies() {
 		if (this.defaultCookies == null) {
 			this.defaultCookies = new LinkedMultiValueMap<>(4);
 		}
+		return this.defaultCookies;
 	}
 
 	@Override
@@ -156,29 +164,28 @@ class DefaultWebClientBuilder implements WebClient.Builder {
 
 	@Override
 	public WebClient.Builder filter(ExchangeFilterFunction filter) {
-		Assert.notNull(filter, "'filter' must not be null");
-		initFilters();
-		this.filters.add(filter);
+		Assert.notNull(filter, "ExchangeFilterFunction must not be null");
+		initFilters().add(filter);
 		return this;
 	}
 
 	@Override
 	public WebClient.Builder filters(Consumer<List<ExchangeFilterFunction>> filtersConsumer) {
-		Assert.notNull(filtersConsumer, "'filtersConsumer' must not be null");
-		initFilters();
-		filtersConsumer.accept(this.filters);
+		Assert.notNull(filtersConsumer, "Filters consumer must not be null");
+		filtersConsumer.accept(initFilters());
 		return this;
 	}
 
-	private void initFilters() {
+	private List<ExchangeFilterFunction> initFilters() {
 		if (this.filters == null) {
 			this.filters = new ArrayList<>();
 		}
+		return this.filters;
 	}
 
 	@Override
 	public WebClient.Builder exchangeStrategies(ExchangeStrategies strategies) {
-		Assert.notNull(strategies, "'strategies' must not be null");
+		Assert.notNull(strategies, "ExchangeStrategies must not be null");
 		this.exchangeStrategies = strategies;
 		return this;
 	}

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

@@ -392,6 +392,7 @@ public interface ServerResponse {
 		Mono<ServerResponse> render(String name, Map<String, ?> model);
 	}
 
+
 	/**
 	 * Defines the context used during the {@link #writeTo(ServerWebExchange, Context)}.
 	 */
@@ -399,13 +400,13 @@ public interface ServerResponse {
 
 		/**
 		 * Return the {@link HttpMessageWriter}s to be used for response body conversion.
-		 * @return the stream of message writers
+		 * @return the list of message writers
 		 */
 		List<HttpMessageWriter<?>> messageWriters();
 
 		/**
 		 * Return the  {@link ViewResolver}s to be used for view name resolution.
-		 * @return the stream of view resolvers
+		 * @return the list of view resolvers
 		 */
 		List<ViewResolver> viewResolvers();
 	}

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

@@ -24,6 +24,8 @@ import reactor.core.publisher.Mono;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.RouterFunctions;
@@ -43,10 +45,13 @@ import org.springframework.web.server.ServerWebExchange;
  */
 public class RouterFunctionMapping extends AbstractHandlerMapping implements InitializingBean {
 
+	@Nullable
 	private RouterFunction<?> routerFunction;
 
+	@Nullable
 	private ServerCodecConfigurer messageCodecConfigurer;
 
+
 	/**
 	 * Create an empty {@code RouterFunctionMapping}.
 	 * <p>If this constructor is used, this mapping will detect all {@link RouterFunction} instances
@@ -64,6 +69,7 @@ public class RouterFunctionMapping extends AbstractHandlerMapping implements Ini
 		this.routerFunction = routerFunction;
 	}
 
+
 	/**
 	 * Configure HTTP message readers to de-serialize the request body with.
 	 * <p>By default this is set to {@link ServerCodecConfigurer} with defaults.
@@ -114,6 +120,7 @@ public class RouterFunctionMapping extends AbstractHandlerMapping implements Ini
 	@Override
 	protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
 		if (this.routerFunction != null) {
+			Assert.state(this.messageCodecConfigurer != null, "No ServerCodecConfigurer set");
 			ServerRequest request = ServerRequest.create(exchange, this.messageCodecConfigurer.getReaders());
 			exchange.getAttributes().put(RouterFunctions.REQUEST_ATTRIBUTE, request);
 			return this.routerFunction.route(request);
@@ -123,8 +130,10 @@ public class RouterFunctionMapping extends AbstractHandlerMapping implements Ini
 		}
 	}
 
+
 	private static class SortedRouterFunctionsContainer {
 
+		@Nullable
 		private List<RouterFunction<?>> routerFunctions;
 
 		@Autowired(required = false)

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

@@ -25,6 +25,7 @@ import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.Ordered;
 import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.HandlerResultHandler;
@@ -38,12 +39,12 @@ import org.springframework.web.server.ServerWebExchange;
  * @author Arjen Poutsma
  * @since 5.0
  */
-public class ServerResponseResultHandler implements HandlerResultHandler, InitializingBean,
-		Ordered {
+public class ServerResponseResultHandler implements HandlerResultHandler, InitializingBean, Ordered {
 
+	@Nullable
 	private ServerCodecConfigurer messageCodecConfigurer;
 
-	private List<ViewResolver> viewResolvers;
+	private List<ViewResolver> viewResolvers = Collections.emptyList();
 
 	private int order = LOWEST_PRECEDENCE;
 
@@ -79,10 +80,7 @@ public class ServerResponseResultHandler implements HandlerResultHandler, Initia
 	@Override
 	public void afterPropertiesSet() throws Exception {
 		if (this.messageCodecConfigurer == null) {
-			throw new IllegalArgumentException("'messageCodecConfigurer' is required");
-		}
-		if (this.viewResolvers == null) {
-			this.viewResolvers = Collections.emptyList();
+			throw new IllegalArgumentException("Property 'messageCodecConfigurer' is required");
 		}
 	}
 
@@ -98,9 +96,9 @@ public class ServerResponseResultHandler implements HandlerResultHandler, Initia
 		return response.writeTo(exchange, new ServerResponse.Context() {
 			@Override
 			public List<HttpMessageWriter<?>> messageWriters() {
-				return messageCodecConfigurer.getWriters();
+				return (messageCodecConfigurer != null ?
+						messageCodecConfigurer.getWriters() : Collections.emptyList());
 			}
-
 			@Override
 			public List<ViewResolver> viewResolvers() {
 				return viewResolvers;

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

@@ -16,6 +16,7 @@
 
 package org.springframework.web.reactive.handler;
 
+import java.util.Collections;
 import java.util.Map;
 import java.util.Optional;
 
@@ -50,11 +51,9 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
 
 	private boolean lazyInitHandlers = false;
 
+	@Nullable
 	private PathPatternRegistry<Object> patternRegistry;
 
-	public PathPatternRegistry<Object> getPatternRegistry() {
-		return patternRegistry;
-	}
 
 	/**
 	 * Set whether to lazily initialize handlers. Only applicable to
@@ -76,7 +75,7 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
 	 * as value.
 	 */
 	public final Map<PathPattern, Object> getHandlerMap() {
-		return this.patternRegistry.getPatternsMap();
+		return (this.patternRegistry != null ? this.patternRegistry.getPatternsMap() : Collections.emptyMap());
 	}
 
 
@@ -103,11 +102,9 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
 
 	/**
 	 * Look up a handler instance for the given URL lookup path.
-	 *
 	 * <p>Supports direct matches, e.g. a registered "/test" matches "/test",
 	 * and various path pattern matches, e.g. a registered "/t*" matches
 	 * both "/test" and "/team". For details, see the PathPattern class.
-	 *
 	 * @param lookupPath URL the handler is mapped to
 	 * @param exchange the current exchange
 	 * @return the associated handler instance, or {@code null} if not found
@@ -115,19 +112,17 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
 	 */
 	@Nullable
 	protected Object lookupHandler(String lookupPath, ServerWebExchange exchange) throws Exception {
-		Optional<PathMatchResult<Object>> matches = this.patternRegistry.findFirstMatch(lookupPath);
-		if (matches.isPresent()) {
-			if (logger.isDebugEnabled()) {
-				logger.debug("Matching patterns for request [" + lookupPath + "] are " + matches);
+		if (this.patternRegistry != null) {
+			Optional<PathMatchResult<Object>> matches = this.patternRegistry.findFirstMatch(lookupPath);
+			if (matches.isPresent()) {
+				if (logger.isDebugEnabled()) {
+					logger.debug("Matching patterns for request [" + lookupPath + "] are " + matches);
+				}
+				PathMatchResult<Object> bestMatch = matches.get();
+				String pathWithinMapping = bestMatch.getPattern().extractPathWithinPattern(lookupPath);
+				Object handler = bestMatch.getHandler();
+				return handleMatch(handler, bestMatch.getPattern(), pathWithinMapping, exchange);
 			}
-			PathMatchResult<Object> bestMatch = matches.get();
-			String pathWithinMapping = bestMatch.getPattern().extractPathWithinPattern(lookupPath);
-			Object handler = bestMatch.getHandler();
-			if (handler == null) {
-				throw new IllegalStateException(
-						"Could not find handler for best pattern match [" + bestMatch + "]");
-			}
-			return handleMatch(handler, bestMatch.getPattern(), pathWithinMapping, exchange);
 		}
 
 		// No handler found...

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

@@ -16,7 +16,6 @@
 
 package org.springframework.web.reactive.handler;
 
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.util.pattern.PathPattern;
 
@@ -37,8 +36,9 @@ public class PathMatchResult<T> {
 	private final T handler;
 
 
-	public PathMatchResult(PathPattern pattern, @Nullable T handler) {
+	public PathMatchResult(PathPattern pattern, T handler) {
 		Assert.notNull(pattern, "PathPattern must not be null");
+		Assert.notNull(handler, "Handler must not be null");
 		this.pattern = pattern;
 		this.handler = handler;
 	}
@@ -54,7 +54,6 @@ public class PathMatchResult<T> {
 	/**
 	 * Return the request handler associated with the {@link PathPattern}.
 	 */
-	@Nullable
 	public T getHandler() {
 		return this.handler;
 	}

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

@@ -164,14 +164,13 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 
 		private final Scanner scanner;
 
+		@Nullable
 		private LineInfo previous;
 
-
 		public LineGenerator(String content) {
 			this.scanner = new Scanner(content);
 		}
 
-
 		@Override
 		public void accept(SynchronousSink<LineInfo> sink) {
 			if (this.scanner.hasNext()) {
@@ -186,6 +185,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 		}
 	}
 
+
 	private static class LineInfo {
 
 		private final String line;
@@ -194,8 +194,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 
 		private final boolean link;
 
-
-		public LineInfo(String line, LineInfo previousLine) {
+		public LineInfo(String line, @Nullable LineInfo previousLine) {
 			this.line = line;
 			this.cacheSection = initCacheSectionFlag(line, previousLine);
 			this.link = iniLinkFlag(line, this.cacheSection);
@@ -222,7 +221,6 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 			return (line.startsWith("//") || (index > 0 && !line.substring(0, index).contains("/")));
 		}
 
-
 		public String getLine() {
 			return this.line;
 		}
@@ -236,13 +234,14 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 		}
 	}
 
+
 	private static class LineOutput {
 
 		private final String line;
 
+		@Nullable
 		private final Resource resource;
 
-
 		public LineOutput(String line, @Nullable Resource resource) {
 			this.line = line;
 			this.resource = resource;
@@ -258,6 +257,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 		}
 	}
 
+
 	private static class LineAggregator {
 
 		private final StringWriter writer = new StringWriter();
@@ -266,7 +266,6 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 
 		private final Resource resource;
 
-
 		public LineAggregator(Resource resource, String content) {
 			this.resource = resource;
 			this.baos = new ByteArrayOutputStream(content.length());

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

@@ -205,9 +205,6 @@ 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/resource/TransformedResource.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,17 +20,19 @@ import java.io.IOException;
 
 import org.springframework.core.io.ByteArrayResource;
 import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
 
 /**
- * An extension of {@link ByteArrayResource}
- * that a {@link ResourceTransformer} can use to represent an original
- * resource preserving all other information except the content.
+ * An extension of {@link ByteArrayResource} that a {@link ResourceTransformer}
+ * can use to represent an original resource preserving all other information
+ * except the content.
  *
  * @author Rossen Stoyanchev
  * @since 5.0
  */
 public class TransformedResource extends ByteArrayResource {
 
+	@Nullable
 	private final String filename;
 
 	private final long lastModified;
@@ -50,6 +52,7 @@ public class TransformedResource extends ByteArrayResource {
 
 
 	@Override
+	@Nullable
 	public String getFilename() {
 		return this.filename;
 	}

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

@@ -48,6 +48,7 @@ import org.springframework.web.util.pattern.PathPatternParser;
  */
 public final class RequestMappingInfo implements RequestCondition<RequestMappingInfo> {
 
+	@Nullable
 	private final String name;
 
 	private final PatternsRequestCondition patternsCondition;
@@ -392,18 +393,25 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 
 		private String[] paths;
 
+		@Nullable
 		private RequestMethod[] methods;
 
+		@Nullable
 		private String[] params;
 
+		@Nullable
 		private String[] headers;
 
+		@Nullable
 		private String[] consumes;
 
+		@Nullable
 		private String[] produces;
 
+		@Nullable
 		private String mappingName;
 
+		@Nullable
 		private RequestCondition<?> customCondition;
 
 		private BuilderConfiguration options = new BuilderConfiguration();
@@ -492,19 +500,21 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	 */
 	public static class BuilderConfiguration {
 
+		@Nullable
 		private PathPatternParser patternParser;
 
+		@Nullable
 		private RequestedContentTypeResolver contentTypeResolver;
 
+		public void setPatternParser(PathPatternParser patternParser) {
+			this.patternParser = patternParser;
+		}
+
 		@Nullable
 		public PathPatternParser getPatternParser() {
 			return this.patternParser;
 		}
 
-		public void setPatternParser(PathPatternParser patternParser) {
-			this.patternParser = patternParser;
-		}
-
 		/**
 		 * Set the ContentNegotiationManager to use for the ProducesRequestCondition.
 		 * <p>By default this is not set.

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

@@ -23,6 +23,7 @@ import java.util.stream.Collectors;
 
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.ParameterNameDiscoverer;
+import org.springframework.lang.Nullable;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.BindingContext;
 import org.springframework.web.reactive.HandlerResult;
@@ -93,6 +94,7 @@ public class SyncInvocableHandlerMethod extends HandlerMethod {
 	 * @param providedArgs optional list of argument values to match by type
 	 * @return Mono with a {@link HandlerResult}.
 	 */
+	@Nullable
 	public HandlerResult invokeForHandlerResult(ServerWebExchange exchange,
 			BindingContext bindingContext, Object... providedArgs) {
 

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

@@ -60,8 +60,10 @@ import org.springframework.web.server.ServerWebInputException;
  */
 public abstract class AbstractNamedValueArgumentResolver extends HandlerMethodArgumentResolverSupport {
 
+	@Nullable
 	private final ConfigurableBeanFactory configurableBeanFactory;
 
+	@Nullable
 	private final BeanExpressionContext expressionContext;
 
 	private final Map<MethodParameter, NamedValueInfo> namedValueInfoCache = new ConcurrentHashMap<>(256);
@@ -154,7 +156,7 @@ public abstract class AbstractNamedValueArgumentResolver extends HandlerMethodAr
 	 */
 	@Nullable
 	private Object resolveStringValue(String value) {
-		if (this.configurableBeanFactory == null) {
+		if (this.configurableBeanFactory == null || this.expressionContext == null) {
 			return value;
 		}
 		String placeholdersResolved = this.configurableBeanFactory.resolveEmbeddedValue(value);
@@ -291,6 +293,7 @@ public abstract class AbstractNamedValueArgumentResolver extends HandlerMethodAr
 
 		private final boolean required;
 
+		@Nullable
 		private final String defaultValue;
 
 		public NamedValueInfo(String name, boolean required, @Nullable String defaultValue) {

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

@@ -52,7 +52,7 @@ import org.springframework.web.reactive.result.method.InvocableHandlerMethod;
 import org.springframework.web.reactive.result.method.SyncHandlerMethodArgumentResolver;
 import org.springframework.web.reactive.result.method.SyncInvocableHandlerMethod;
 
-import static org.springframework.core.MethodIntrospector.selectMethods;
+import static org.springframework.core.MethodIntrospector.*;
 
 /**
  * Package-private class to assist {@link RequestMappingHandlerAdapter} with
@@ -218,7 +218,6 @@ class ControllerMethodResolver {
 	 * or in the controller of the given {@code @RequestMapping} method.
 	 */
 	public List<SyncInvocableHandlerMethod> getInitBinderMethods(HandlerMethod handlerMethod) {
-
 		List<SyncInvocableHandlerMethod> result = new ArrayList<>();
 		Class<?> handlerType = handlerMethod.getBeanType();
 
@@ -251,7 +250,6 @@ class ControllerMethodResolver {
 	 * components or in the controller of the given {@code @RequestMapping} method.
 	 */
 	public List<InvocableHandlerMethod> getModelAttributeMethods(HandlerMethod handlerMethod) {
-
 		List<InvocableHandlerMethod> result = new ArrayList<>();
 		Class<?> handlerType = handlerMethod.getBeanType();
 
@@ -331,18 +329,18 @@ class ControllerMethodResolver {
 
 		private final List<HandlerMethodArgumentResolver> customResolvers;
 
+		@Nullable
 		private final List<HttpMessageReader<?>> messageReaders;
 
 		private final boolean modelAttributeSupported;
 
 		private final List<HandlerMethodArgumentResolver> result = new ArrayList<>();
 
-
 		private ArgumentResolverRegistrar(ArgumentResolverConfigurer resolvers,
 				@Nullable ServerCodecConfigurer codecs, boolean modelAttribute) {
 
 			this.customResolvers = resolvers.getCustomResolvers();
-			this.messageReaders = codecs != null ? codecs.getReaders() : null;
+			this.messageReaders = (codecs != null ? codecs.getReaders() : null);
 			this.modelAttributeSupported = modelAttribute;
 		}
 
@@ -379,7 +377,6 @@ class ControllerMethodResolver {
 					.collect(Collectors.toList());
 		}
 
-
 		public static Builder configurer(ArgumentResolverConfigurer configurer) {
 			return new Builder(configurer);
 		}
@@ -389,12 +386,10 @@ class ControllerMethodResolver {
 
 			private final ArgumentResolverConfigurer resolvers;
 
-
 			public Builder(ArgumentResolverConfigurer configurer) {
 				this.resolvers = configurer;
 			}
 
-
 			public ArgumentResolverRegistrar fullSupport(ServerCodecConfigurer codecs) {
 				return new ArgumentResolverRegistrar(this.resolvers, codecs, true);
 			}
@@ -407,7 +402,6 @@ class ControllerMethodResolver {
 				return new ArgumentResolverRegistrar(this.resolvers, null, false);
 			}
 		}
-
 	}
 
 }

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

@@ -26,6 +26,7 @@ import org.springframework.web.bind.annotation.InitBinder;
 import org.springframework.web.bind.support.WebBindingInitializer;
 import org.springframework.web.bind.support.WebExchangeDataBinder;
 import org.springframework.web.reactive.BindingContext;
+import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.result.method.SyncInvocableHandlerMethod;
 import org.springframework.web.server.ServerWebExchange;
 
@@ -71,10 +72,10 @@ class InitBinderBindingContext extends BindingContext {
 	private void invokeBinderMethod(WebExchangeDataBinder dataBinder,
 			ServerWebExchange exchange, SyncInvocableHandlerMethod binderMethod) {
 
-		Object returnValue = binderMethod.invokeForHandlerResult(exchange, this.binderMethodContext, dataBinder)
-				.getReturnValue();
+		HandlerResult result = binderMethod.invokeForHandlerResult(
+				exchange, this.binderMethodContext, dataBinder);
 
-		if (returnValue != null) {
+		if (result != null && result.getReturnValue() != null) {
 			throw new IllegalStateException(
 					"@InitBinder methods should return void: " + binderMethod);
 		}

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

@@ -50,18 +50,25 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 	private static final Log logger = LogFactory.getLog(RequestMappingHandlerAdapter.class);
 
 
+	@Nullable
 	private ServerCodecConfigurer messageCodecConfigurer;
 
+	@Nullable
 	private WebBindingInitializer webBindingInitializer;
 
+	@Nullable
 	private ArgumentResolverConfigurer argumentResolverConfigurer;
 
+	@Nullable
 	private ReactiveAdapterRegistry reactiveAdapterRegistry;
 
+	@Nullable
 	private ConfigurableApplicationContext applicationContext;
 
+	@Nullable
 	private ControllerMethodResolver methodResolver;
 
+	@Nullable
 	private ModelInitializer modelInitializer;
 
 
@@ -76,6 +83,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 	/**
 	 * Return the configurer for HTTP message readers.
 	 */
+	@Nullable
 	public ServerCodecConfigurer getMessageCodecConfigurer() {
 		return this.messageCodecConfigurer;
 	}
@@ -107,6 +115,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 	/**
 	 * Return the configured resolvers for controller method arguments.
 	 */
+	@Nullable
 	public ArgumentResolverConfigurer getArgumentResolverConfigurer() {
 		return this.argumentResolverConfigurer;
 	}
@@ -123,6 +132,7 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 	/**
 	 * Return the configured registry for adapting reactive types.
 	 */
+	@Nullable
 	public ReactiveAdapterRegistry getReactiveAdapterRegistry() {
 		return this.reactiveAdapterRegistry;
 	}
@@ -139,22 +149,17 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 		}
 	}
 
-	public ConfigurableApplicationContext getApplicationContext() {
-		return this.applicationContext;
-	}
-
 
 	@Override
 	public void afterPropertiesSet() throws Exception {
+		Assert.notNull(this.applicationContext, "ApplicationContext is required");
 
 		if (this.messageCodecConfigurer == null) {
 			this.messageCodecConfigurer = ServerCodecConfigurer.create();
 		}
-
 		if (this.argumentResolverConfigurer == null) {
 			this.argumentResolverConfigurer = new ArgumentResolverConfigurer();
 		}
-
 		if (this.reactiveAdapterRegistry == null) {
 			this.reactiveAdapterRegistry = new ReactiveAdapterRegistry();
 		}
@@ -173,9 +178,8 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 
 	@Override
 	public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
-
-		Assert.notNull(handler, "Expected handler");
 		HandlerMethod handlerMethod = (HandlerMethod) handler;
+		Assert.state(this.methodResolver != null && this.modelInitializer != null, "Not initialized");
 
 		BindingContext bindingContext = new InitBinderBindingContext(
 				getWebBindingInitializer(), this.methodResolver.getInitBinderMethods(handlerMethod));
@@ -197,6 +201,8 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Application
 	private Mono<HandlerResult> handleException(Throwable ex, HandlerMethod handlerMethod,
 			BindingContext bindingContext, ServerWebExchange exchange) {
 
+		Assert.state(this.methodResolver != null, "Not initialized");
+
 		InvocableHandlerMethod invocable = this.methodResolver.getExceptionHandlerMethod(ex, handlerMethod);
 		if (invocable != null) {
 			try {

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

@@ -50,6 +50,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 
 	private RequestedContentTypeResolver contentTypeResolver = new RequestedContentTypeResolverBuilder().build();
 
+	@Nullable
 	private StringValueResolver embeddedValueResolver;
 
 	private RequestMappingInfo.BuilderConfiguration config = new RequestMappingInfo.BuilderConfiguration();

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

@@ -62,8 +62,10 @@ public abstract class AbstractView implements View, ApplicationContextAware {
 
 	private Charset defaultCharset = StandardCharsets.UTF_8;
 
+	@Nullable
 	private String requestContextAttribute;
 
+	@Nullable
 	private ApplicationContext applicationContext;
 
 

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

@@ -24,6 +24,7 @@ import org.springframework.beans.BeanWrapper;
 import org.springframework.beans.PropertyAccessorFactory;
 import org.springframework.context.NoSuchMessageException;
 import org.springframework.lang.Nullable;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.validation.BindingResult;
 import org.springframework.validation.Errors;
@@ -51,25 +52,34 @@ public class BindStatus {
 
 	private final boolean htmlEscape;
 
+	@Nullable
 	private final String expression;
 
+	@Nullable
 	private final Errors errors;
 
 
+	@Nullable
 	private BindingResult bindingResult;
 
+	@Nullable
 	private Object value;
 
+	@Nullable
 	private Class<?> valueType;
 
+	@Nullable
 	private Object actualValue;
 
+	@Nullable
 	private PropertyEditor editor;
 
+	@Nullable
 	private List<? extends ObjectError> objectErrors;
 
-	private String[] errorCodes;
+	private String[] errorCodes = new String[0];
 
+	@Nullable
 	private String[] errorMessages;
 
 
@@ -244,14 +254,13 @@ public class BindStatus {
 	 * Return if this status represents a field or object error.
 	 */
 	public boolean isError() {
-		return (this.errorCodes != null && this.errorCodes.length > 0);
+		return (this.errorCodes.length > 0);
 	}
 
 	/**
 	 * Return the error codes for the field or object, if any.
 	 * Returns an empty array instead of null if none.
 	 */
-	@Nullable
 	public String[] getErrorCodes() {
 		return this.errorCodes;
 	}
@@ -260,7 +269,7 @@ public class BindStatus {
 	 * Return the first error codes for the field or object, if any.
 	 */
 	public String getErrorCode() {
-		return (this.errorCodes.length > 0 ? this.errorCodes[0] : "");
+		return (!ObjectUtils.isEmpty(this.errorCodes) ? this.errorCodes[0] : "");
 	}
 
 	/**
@@ -268,16 +277,15 @@ public class BindStatus {
 	 * if any. Returns an empty array instead of null if none.
 	 */
 	public String[] getErrorMessages() {
-		initErrorMessages();
-		return this.errorMessages;
+		return initErrorMessages();
 	}
 
 	/**
 	 * Return the first error message for the field or object, if any.
 	 */
 	public String getErrorMessage() {
-		initErrorMessages();
-		return (this.errorMessages.length > 0 ? this.errorMessages[0] : "");
+		String[] errorMessages = initErrorMessages();
+		return (errorMessages.length > 0 ? errorMessages[0] : "");
 	}
 
 	/**
@@ -287,21 +295,26 @@ public class BindStatus {
 	 * @return the error message string
 	 */
 	public String getErrorMessagesAsString(String delimiter) {
-		initErrorMessages();
-		return StringUtils.arrayToDelimitedString(this.errorMessages, delimiter);
+		return StringUtils.arrayToDelimitedString(initErrorMessages(), delimiter);
 	}
 
 	/**
 	 * Extract the error messages from the ObjectError list.
 	 */
-	private void initErrorMessages() throws NoSuchMessageException {
+	private String[] initErrorMessages() throws NoSuchMessageException {
 		if (this.errorMessages == null) {
-			this.errorMessages = new String[this.objectErrors.size()];
-			for (int i = 0; i < this.objectErrors.size(); i++) {
-				ObjectError error = this.objectErrors.get(i);
-				this.errorMessages[i] = this.requestContext.getMessage(error, this.htmlEscape);
+			if (this.objectErrors != null) {
+				this.errorMessages = new String[this.objectErrors.size()];
+				for (int i = 0; i < this.objectErrors.size(); i++) {
+					ObjectError error = this.objectErrors.get(i);
+					this.errorMessages[i] = this.requestContext.getMessage(error, this.htmlEscape);
+				}
+			}
+			else {
+				this.errorMessages = new String[0];
 			}
 		}
+		return this.errorMessages;
 	}
 
 	/**
@@ -343,7 +356,7 @@ public class BindStatus {
 		StringBuilder sb = new StringBuilder("BindStatus: ");
 		sb.append("expression=[").append(this.expression).append("]; ");
 		sb.append("value=[").append(this.value).append("]");
-		if (isError()) {
+		if (!ObjectUtils.isEmpty(this.errorCodes)) {
 			sb.append("; errorCodes=").append(Arrays.asList(this.errorCodes));
 		}
 		return sb.toString();

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

@@ -39,12 +39,13 @@ class DefaultRendering implements Rendering {
 
 	private final Map<String, Object> model;
 
+	@Nullable
 	private final HttpStatus status;
 
 	private final HttpHeaders headers;
 
 
-	DefaultRendering(Object view, @Nullable Model model, HttpStatus status, @Nullable HttpHeaders headers) {
+	DefaultRendering(Object view, @Nullable Model model, @Nullable HttpStatus status, @Nullable HttpHeaders headers) {
 		this.view = view;
 		this.model = (model != null ? model.asMap() : Collections.emptyMap());
 		this.status = status;
@@ -63,6 +64,7 @@ class DefaultRendering implements Rendering {
 	}
 
 	@Override
+	@Nullable
 	public HttpStatus status() {
 		return this.status;
 	}

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

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.web.reactive.result.view;
 
 import java.util.Arrays;
@@ -20,6 +21,7 @@ import java.util.Map;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
+import org.springframework.lang.Nullable;
 import org.springframework.ui.ExtendedModelMap;
 import org.springframework.ui.Model;
 import org.springframework.util.Assert;
@@ -34,10 +36,13 @@ class DefaultRenderingBuilder implements Rendering.RedirectBuilder {
 
 	private final Object view;
 
+	@Nullable
 	private Model model;
 
+	@Nullable
 	private HttpStatus status;
 
+	@Nullable
 	private HttpHeaders headers;
 
 
@@ -48,38 +53,35 @@ class DefaultRenderingBuilder implements Rendering.RedirectBuilder {
 
 	@Override
 	public DefaultRenderingBuilder modelAttribute(String name, Object value) {
-		initModel();
-		this.model.addAttribute(name, value);
+		initModel().addAttribute(name, value);
 		return this;
 	}
 
-	private void initModel() {
-		if (this.model == null) {
-			this.model = new ExtendedModelMap();
-		}
-	}
-
 	@Override
 	public DefaultRenderingBuilder modelAttribute(Object value) {
-		initModel();
-		this.model.addAttribute(value);
+		initModel().addAttribute(value);
 		return this;
 	}
 
 	@Override
 	public DefaultRenderingBuilder modelAttributes(Object... values) {
-		initModel();
-		this.model.addAllAttributes(Arrays.asList(values));
+		initModel().addAllAttributes(Arrays.asList(values));
 		return this;
 	}
 
 	@Override
 	public DefaultRenderingBuilder model(Map<String, ?> map) {
-		initModel();
-		this.model.addAllAttributes(map);
+		initModel().addAllAttributes(map);
 		return this;
 	}
 
+	private Model initModel() {
+		if (this.model == null) {
+			this.model = new ExtendedModelMap();
+		}
+		return this.model;
+	}
+
 	@Override
 	public DefaultRenderingBuilder status(HttpStatus status) {
 		this.status = status;
@@ -88,22 +90,21 @@ class DefaultRenderingBuilder implements Rendering.RedirectBuilder {
 
 	@Override
 	public DefaultRenderingBuilder header(String headerName, String... headerValues) {
-		initHeaders();
-		this.headers.put(headerName, Arrays.asList(headerValues));
+		initHeaders().put(headerName, Arrays.asList(headerValues));
 		return this;
 	}
 
 	@Override
 	public DefaultRenderingBuilder headers(HttpHeaders headers) {
-		initHeaders();
-		this.headers.putAll(headers);
+		initHeaders().putAll(headers);
 		return this;
 	}
 
-	private void initHeaders() {
+	private HttpHeaders initHeaders() {
 		if (this.headers == null) {
 			this.headers = new HttpHeaders();
 		}
+		return this.headers;
 	}
 
 	@Override
@@ -123,6 +124,7 @@ class DefaultRenderingBuilder implements Rendering.RedirectBuilder {
 		return (RedirectView) this.view;
 	}
 
+
 	@Override
 	public Rendering build() {
 		return new DefaultRendering(this.view, this.model, this.status, this.headers);

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

@@ -65,10 +65,13 @@ public class RequestContext {
 
 	private TimeZone timeZone;
 
+	@Nullable
 	private Boolean defaultHtmlEscape;
 
+	@Nullable
 	private Map<String, Errors> errorsMap;
 
+	@Nullable
 	private RequestDataValueProcessor dataValueProcessor;
 
 
@@ -79,19 +82,21 @@ public class RequestContext {
 	public RequestContext(ServerWebExchange exchange, Map<String, Object> model, MessageSource messageSource,
 			@Nullable RequestDataValueProcessor dataValueProcessor) {
 
-		Assert.notNull(exchange, "'exchange' is required");
-		Assert.notNull(model, "'model' is required");
-		Assert.notNull(messageSource, "'messageSource' is required");
+		Assert.notNull(exchange, "ServerWebExchange is required");
+		Assert.notNull(model, "Model is required");
+		Assert.notNull(messageSource, "MessageSource is required");
 		this.exchange = exchange;
 		this.model = model;
 		this.messageSource = messageSource;
 
 		LocaleContext localeContext = exchange.getLocaleContext();
-		this.locale = localeContext.getLocale();
-		this.timeZone = (localeContext instanceof TimeZoneAwareLocaleContext ?
-				((TimeZoneAwareLocaleContext)localeContext).getTimeZone() : TimeZone.getDefault());
+		Locale locale = localeContext.getLocale();
+		this.locale = (locale != null ? locale : Locale.getDefault());
+		TimeZone timeZone = (localeContext instanceof TimeZoneAwareLocaleContext ?
+				((TimeZoneAwareLocaleContext) localeContext).getTimeZone() : null);
+		this.timeZone = (timeZone != null ? timeZone : TimeZone.getDefault());
 
-		this.defaultHtmlEscape = null; // TODO
+		this.defaultHtmlEscape = null;  // TODO
 		this.dataValueProcessor = dataValueProcessor;
 	}
 
@@ -125,7 +130,6 @@ public class RequestContext {
 
 	/**
 	 * Return the current TimeZone.
-	 * TODO: currently this is the Timezone.getDefault()
 	 */
 	public TimeZone getTimeZone() {
 		return this.timeZone;
@@ -168,6 +172,7 @@ public class RequestContext {
 	 * specified and an explicit value.
 	 * @return whether default HTML escaping is enabled (null = no explicit default)
 	 */
+	@Nullable
 	public Boolean getDefaultHtmlEscape() {
 		return this.defaultHtmlEscape;
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,9 @@ import freemarker.template.TemplateException;
 
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.context.ResourceLoaderAware;
+import org.springframework.lang.Nullable;
 import org.springframework.ui.freemarker.FreeMarkerConfigurationFactory;
+import org.springframework.util.Assert;
 
 /**
  * Configures FreeMarker for web usage via the "configLocation" and/or
@@ -62,6 +64,7 @@ import org.springframework.ui.freemarker.FreeMarkerConfigurationFactory;
 public class FreeMarkerConfigurer extends FreeMarkerConfigurationFactory
 		implements FreeMarkerConfig, InitializingBean, ResourceLoaderAware {
 
+	@Nullable
 	private Configuration configuration;
 
 
@@ -111,7 +114,8 @@ public class FreeMarkerConfigurer extends FreeMarkerConfigurationFactory
 	 */
 	@Override
 	public Configuration getConfiguration() {
+		Assert.state(this.configuration != null, "No Configuration available");
 		return this.configuration;
 	}
 
-}
+}

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

@@ -37,7 +37,6 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextException;
 import org.springframework.context.i18n.LocaleContextHolder;
 import org.springframework.core.io.Resource;
-import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.reactive.ServerHttpResponse;
@@ -74,22 +73,28 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 	private static final String DEFAULT_RESOURCE_LOADER_PATH = "classpath:";
 
 
+	@Nullable
 	private ScriptEngine engine;
 
+	@Nullable
 	private String engineName;
 
+	@Nullable
 	private Boolean sharedEngine;
 
+	@Nullable
 	private String[] scripts;
 
+	@Nullable
 	private String renderObject;
 
+	@Nullable
 	private String renderFunction;
 
+	@Nullable
 	private String[] resourceLoaderPaths;
 
-	private ResourceLoader resourceLoader;
-
+	@Nullable
 	private volatile ScriptEngineManager scriptEngineManager;
 
 
@@ -193,9 +198,6 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 			String resourceLoaderPath = viewConfig.getResourceLoaderPath();
 			setResourceLoaderPath(resourceLoaderPath == null ? DEFAULT_RESOURCE_LOADER_PATH : resourceLoaderPath);
 		}
-		if (this.resourceLoader == null) {
-			this.resourceLoader = getApplicationContext();
-		}
 		if (this.sharedEngine == null && viewConfig.isSharedEngine() != null) {
 			this.sharedEngine = viewConfig.isSharedEngine();
 		}
@@ -214,24 +216,34 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 			loadScripts(this.engine);
 		}
 		else {
-			setEngine(createEngineFromName());
+			setEngine(createEngineFromName(this.engineName));
 		}
 
 		if (this.renderFunction != null && this.engine != null) {
-			Assert.isInstanceOf(Invocable.class, this.engine, "ScriptEngine must implement Invocable when 'renderFunction' is specified.");
+			Assert.isInstanceOf(Invocable.class, this.engine,
+					"ScriptEngine must implement Invocable when 'renderFunction' is specified");
 		}
 	}
 
 	protected ScriptEngine getEngine() {
-		return Boolean.FALSE.equals(this.sharedEngine) ? createEngineFromName() : this.engine;
+		if (Boolean.FALSE.equals(this.sharedEngine)) {
+			Assert.state(this.engineName != null, "No engine name specified");
+			return createEngineFromName(this.engineName);
+		}
+		else {
+			Assert.state(this.engine != null, "No shared engine available");
+			return this.engine;
+		}
 	}
 
-	protected ScriptEngine createEngineFromName() {
-		if (this.scriptEngineManager == null) {
-			this.scriptEngineManager = new ScriptEngineManager(obtainApplicationContext().getClassLoader());
+	protected ScriptEngine createEngineFromName(String engineName) {
+		ScriptEngineManager scriptEngineManager = this.scriptEngineManager;
+		if (scriptEngineManager == null) {
+			scriptEngineManager = new ScriptEngineManager(obtainApplicationContext().getClassLoader());
+			this.scriptEngineManager = scriptEngineManager;
 		}
 
-		ScriptEngine engine = StandardScriptUtils.retrieveEngineByName(this.scriptEngineManager, this.engineName);
+		ScriptEngine engine = StandardScriptUtils.retrieveEngineByName(scriptEngineManager, engineName);
 		loadScripts(engine);
 		return engine;
 	}
@@ -255,10 +267,12 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 
 	@Nullable
 	protected Resource getResource(String location) {
-		for (String path : this.resourceLoaderPaths) {
-			Resource resource = this.resourceLoader.getResource(path + location);
-			if (resource.exists()) {
-				return resource;
+		if (this.resourceLoaderPaths != null) {
+			for (String path : this.resourceLoaderPaths) {
+				Resource resource = obtainApplicationContext().getResource(path + location);
+				if (resource.exists()) {
+					return resource;
+				}
 			}
 		}
 		return null;
@@ -317,10 +331,10 @@ public class ScriptTemplateView extends AbstractUrlBasedView {
 				}
 				else if (this.renderObject != null) {
 					Object thiz = engine.eval(this.renderObject);
-					html = ((Invocable)engine).invokeMethod(thiz, this.renderFunction, template, model, context);
+					html = ((Invocable) engine).invokeMethod(thiz, this.renderFunction, template, model, context);
 				}
 				else {
-					html = ((Invocable)engine).invokeFunction(this.renderFunction, template, model, context);
+					html = ((Invocable) engine).invokeFunction(this.renderFunction, template, model, context);
 				}
 
 				byte[] bytes = String.valueOf(html).getBytes(StandardCharsets.UTF_8);

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

@@ -135,6 +135,7 @@ public final class CloseStatus {
 
 	private final int code;
 
+	@Nullable
 	private final String reason;
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/socket/HandshakeInfo.java

@@ -41,6 +41,7 @@ public class HandshakeInfo {
 
 	private final HttpHeaders headers;
 
+	@Nullable
 	private final String protocol;
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/AbstractListenerWebSocketSession.java

@@ -30,6 +30,7 @@ import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.http.server.reactive.AbstractListenerReadPublisher;
 import org.springframework.http.server.reactive.AbstractListenerWriteProcessor;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.web.reactive.socket.CloseStatus;
 import org.springframework.web.reactive.socket.HandshakeInfo;
 import org.springframework.web.reactive.socket.WebSocketMessage;
@@ -58,10 +59,12 @@ public abstract class AbstractListenerWebSocketSession<T> extends AbstractWebSoc
 	private static final int RECEIVE_BUFFER_SIZE = 8192;
 
 
+	@Nullable
 	private final MonoProcessor<Void> completionMono;
 
 	private final WebSocketReceivePublisher receivePublisher = new WebSocketReceivePublisher();
 
+	@Nullable
 	private volatile WebSocketSendProcessor sendProcessor;
 
 	private final AtomicBoolean sendCalled = new AtomicBoolean();
@@ -93,7 +96,9 @@ public abstract class AbstractListenerWebSocketSession<T> extends AbstractWebSoc
 
 
 	protected WebSocketSendProcessor getSendProcessor() {
-		return this.sendProcessor;
+		WebSocketSendProcessor sendProcessor = this.sendProcessor;
+		Assert.state(sendProcessor != null, "No WebSocketSendProcessor available");
+		return sendProcessor;
 	}
 
 	@Override
@@ -106,10 +111,11 @@ public abstract class AbstractListenerWebSocketSession<T> extends AbstractWebSoc
 	@Override
 	public Mono<Void> send(Publisher<WebSocketMessage> messages) {
 		if (this.sendCalled.compareAndSet(false, true)) {
-			this.sendProcessor = new WebSocketSendProcessor();
+			WebSocketSendProcessor sendProcessor = new WebSocketSendProcessor();
+			this.sendProcessor = sendProcessor;
 			return Mono.from(subscriber -> {
-					messages.subscribe(this.sendProcessor);
-					this.sendProcessor.subscribe(subscriber);
+					messages.subscribe(sendProcessor);
+					sendProcessor.subscribe(subscriber);
 			});
 		}
 		else {
@@ -157,18 +163,20 @@ public abstract class AbstractListenerWebSocketSession<T> extends AbstractWebSoc
 	/** Handle an error callback from the WebSocketHandler adapter */
 	void handleError(Throwable ex) {
 		this.receivePublisher.onError(ex);
-		if (this.sendProcessor != null) {
-			this.sendProcessor.cancel();
-			this.sendProcessor.onError(ex);
+		WebSocketSendProcessor sendProcessor = this.sendProcessor;
+		if (sendProcessor != null) {
+			sendProcessor.cancel();
+			sendProcessor.onError(ex);
 		}
 	}
 
 	/** Handle a close callback from the WebSocketHandler adapter */
 	void handleClose(CloseStatus reason) {
 		this.receivePublisher.onAllDataRead();
-		if (this.sendProcessor != null) {
-			this.sendProcessor.cancel();
-			this.sendProcessor.onComplete();
+		WebSocketSendProcessor sendProcessor = this.sendProcessor;
+		if (sendProcessor != null) {
+			sendProcessor.cancel();
+			sendProcessor.onComplete();
 		}
 	}
 
@@ -205,6 +213,7 @@ public abstract class AbstractListenerWebSocketSession<T> extends AbstractWebSoc
 
 	private final class WebSocketReceivePublisher extends AbstractListenerReadPublisher<WebSocketMessage> {
 
+		@Nullable
 		private volatile WebSocketMessage webSocketMessage;
 
 		@Override

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/JettyWebSocketHandlerAdapter.java

@@ -31,6 +31,7 @@ import org.eclipse.jetty.websocket.api.extensions.Frame;
 import org.eclipse.jetty.websocket.common.OpCode;
 
 import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.socket.CloseStatus;
 import org.springframework.web.reactive.socket.WebSocketHandler;
@@ -56,6 +57,7 @@ public class JettyWebSocketHandlerAdapter {
 
 	private final Function<Session, JettyWebSocketSession> sessionFactory;
 
+	@Nullable
 	private JettyWebSocketSession delegateSession;
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/JettyWebSocketSession.java

@@ -45,6 +45,7 @@ import org.springframework.web.reactive.socket.WebSocketSession;
  */
 public class JettyWebSocketSession extends AbstractListenerWebSocketSession<Session> {
 
+	@Nullable
 	private volatile SuspendToken suspendToken;
 
 

spring-webflux/src/main/java/org/springframework/web/reactive/socket/adapter/StandardWebSocketHandlerAdapter.java

@@ -26,6 +26,7 @@ import javax.websocket.PongMessage;
 import javax.websocket.Session;
 
 import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.socket.CloseStatus;
 import org.springframework.web.reactive.socket.WebSocketHandler;
@@ -47,6 +48,7 @@ public class StandardWebSocketHandlerAdapter extends Endpoint {
 
 	private Function<Session, StandardWebSocketSession> sessionFactory;
 
+	@Nullable
 	private StandardWebSocketSession delegateSession;
 
 
@@ -62,8 +64,8 @@ public class StandardWebSocketHandlerAdapter extends Endpoint {
 
 	@Override
 	public void onOpen(Session session, EndpointConfig config) {
-
 		this.delegateSession = this.sessionFactory.apply(session);
+		Assert.state(this.delegateSession != null, "No delegate session");
 
 		session.addMessageHandler(String.class, message -> {
 			WebSocketMessage webSocketMessage = toMessage(message);

spring-webflux/src/main/java/org/springframework/web/reactive/socket/client/UndertowWebSocketClient.java

@@ -35,6 +35,7 @@ import reactor.core.publisher.MonoProcessor;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.http.HttpHeaders;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.socket.HandshakeInfo;
 import org.springframework.web.reactive.socket.WebSocketHandler;
@@ -184,6 +185,7 @@ public class UndertowWebSocketClient extends WebSocketClientSupport implements W
 
 		private final HttpHeaders responseHeaders = new HttpHeaders();
 
+		@Nullable
 		private final WebSocketClientNegotiation delegate;
 
 		public DefaultNegotiation(List<String> protocols, HttpHeaders requestHeaders,

spring-webflux/src/main/java/org/springframework/web/reactive/socket/server/upgrade/JettyRequestUpgradeStrategy.java

@@ -54,8 +54,10 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 			new NamedThreadLocal<>("JettyWebSocketHandlerAdapter");
 
 
+	@Nullable
 	private WebSocketServerFactory factory;
 
+	@Nullable
 	private volatile ServletContext servletContext;
 
 	private volatile boolean running = false;
@@ -66,10 +68,11 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 	@Override
 	public void start() {
 		synchronized (this.lifecycleMonitor) {
-			if (!isRunning() && this.servletContext != null) {
+			ServletContext servletContext = this.servletContext;
+			if (!isRunning() && servletContext != null) {
 				this.running = true;
 				try {
-					this.factory = new WebSocketServerFactory(this.servletContext);
+					this.factory = new WebSocketServerFactory(servletContext);
 					this.factory.setCreator((request, response) -> {
 						WebSocketHandlerContainer container = adapterHolder.get();
 						String protocol = container.getProtocol();
@@ -92,11 +95,13 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 		synchronized (this.lifecycleMonitor) {
 			if (isRunning()) {
 				this.running = false;
-				try {
-					this.factory.stop();
-				}
-				catch (Throwable ex) {
-					throw new IllegalStateException("Failed to stop WebSocketServerFactory", ex);
+				if (this.factory != null) {
+					try {
+						this.factory.stop();
+					}
+					catch (Throwable ex) {
+						throw new IllegalStateException("Failed to stop WebSocketServerFactory", ex);
+					}
 				}
 			}
 		}
@@ -125,6 +130,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 
 		startLazily(servletRequest);
 
+		Assert.state(this.factory != null, "No WebSocketServerFactory available");
 		boolean isUpgrade = this.factory.isUpgradeRequest(servletRequest, servletResponse);
 		Assert.isTrue(isUpgrade, "Not a WebSocket handshake");
 
@@ -175,6 +181,7 @@ public class JettyRequestUpgradeStrategy implements RequestUpgradeStrategy, Life
 
 		private final JettyWebSocketHandlerAdapter adapter;
 
+		@Nullable
 		private final String protocol;
 
 		public WebSocketHandlerContainer(JettyWebSocketHandlerAdapter adapter, @Nullable String protocol) {

spring-webflux/src/test/java/org/springframework/web/reactive/config/WebFluxConfigurationSupportTests.java

@@ -261,8 +261,6 @@ public class WebFluxConfigurationSupportTests {
 
 		assertEquals(Ordered.LOWEST_PRECEDENCE - 1, handlerMapping.getOrder());
 
-		assertNotNull(handlerMapping.getPatternRegistry());
-
 		SimpleUrlHandlerMapping urlHandlerMapping = (SimpleUrlHandlerMapping) handlerMapping;
 		WebHandler webHandler = (WebHandler) urlHandlerMapping.getUrlMap().get("/images/**");
 		assertNotNull(webHandler);