Empty body checks in ConsumesRequestCondition

Normally consumes matches the "Content-Type" header but what should be done if
there is no content? This commit adds checks for method parameters with
@RequestBody(required=false) and if "false" then also match requests with no content.

Closes gh-22010

spring-webflux/src/main/java/org/springframework/web/reactive/result/condition/ConsumesRequestCondition.java

@@ -23,10 +23,13 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.InvalidMediaTypeException;
 import org.springframework.http.MediaType;
+import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.cors.reactive.CorsUtils;
 import org.springframework.web.server.ServerWebExchange;
@@ -50,6 +53,8 @@ public final class ConsumesRequestCondition extends AbstractRequestCondition<Con
 
 	private final List<ConsumeMediaTypeExpression> expressions;
 
+	private boolean bodyRequired = true;
+
 
 	/**
 	 * Creates a new instance from 0 or more "consumes" expressions.
@@ -141,6 +146,29 @@ public final class ConsumesRequestCondition extends AbstractRequestCondition<Con
 		return " || ";
 	}
 
+	/**
+	 * Whether this condition should expect requests to have a body.
+	 * <p>By default this is set to {@code true} in which case it is assumed a
+	 * request body is required and this condition matches to the "Content-Type"
+	 * header or falls back on "Content-Type: application/octet-stream".
+	 * <p>If set to {@code false}, and the request does not have a body, then this
+	 * condition matches automatically, i.e. without checking expressions.
+	 * @param bodyRequired whether requests are expected to have a body
+	 * @since 5.2
+	 */
+	public void setBodyRequired(boolean bodyRequired) {
+		this.bodyRequired = bodyRequired;
+	}
+
+	/**
+	 * Return the setting for {@link #setBodyRequired(boolean)}.
+	 * @since 5.2
+	 */
+	public boolean isBodyRequired() {
+		return this.bodyRequired;
+	}
+
+
 	/**
 	 * Returns the "other" instance if it has any expressions; returns "this"
 	 * instance otherwise. Practically that means a method-level "consumes"
@@ -163,16 +191,27 @@ public final class ConsumesRequestCondition extends AbstractRequestCondition<Con
 	 */
 	@Override
 	public ConsumesRequestCondition getMatchingCondition(ServerWebExchange exchange) {
-		if (CorsUtils.isPreFlightRequest(exchange.getRequest())) {
+		ServerHttpRequest request = exchange.getRequest();
+		if (CorsUtils.isPreFlightRequest(request)) {
 			return EMPTY_CONDITION;
 		}
 		if (isEmpty()) {
 			return this;
 		}
+		if (!hasBody(request) && !this.bodyRequired) {
+			return EMPTY_CONDITION;
+		}
 		List<ConsumeMediaTypeExpression> result = getMatchingExpressions(exchange);
 		return !CollectionUtils.isEmpty(result) ? new ConsumesRequestCondition(result) : null;
 	}
 
+	private boolean hasBody(ServerHttpRequest request) {
+		String contentLength = request.getHeaders().getFirst(HttpHeaders.CONTENT_LENGTH);
+		String transferEncoding = request.getHeaders().getFirst(HttpHeaders.TRANSFER_ENCODING);
+		return StringUtils.hasText(transferEncoding) ||
+				(StringUtils.hasText(contentLength) && !contentLength.trim().equals("0"));
+	}
+
 	@Nullable
 	private List<ConsumeMediaTypeExpression> getMatchingExpressions(ServerWebExchange exchange) {
 		List<ConsumeMediaTypeExpression> result = null;

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

@@ -18,6 +18,7 @@ package org.springframework.web.reactive.result.method.annotation;
 
 import java.lang.reflect.AnnotatedElement;
 import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -25,6 +26,8 @@ import java.util.function.Predicate;
 
 import org.springframework.context.EmbeddedValueResolverAware;
 import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.core.annotation.MergedAnnotation;
+import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Controller;
 import org.springframework.util.Assert;
@@ -32,12 +35,14 @@ import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.util.StringValueResolver;
 import org.springframework.web.bind.annotation.CrossOrigin;
+import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolverBuilder;
+import org.springframework.web.reactive.result.condition.ConsumesRequestCondition;
 import org.springframework.web.reactive.result.condition.RequestCondition;
 import org.springframework.web.reactive.result.method.RequestMappingInfo;
 import org.springframework.web.reactive.result.method.RequestMappingInfoHandlerMapping;
@@ -255,6 +260,31 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 		}
 	}
 
+	@Override
+	public void registerMapping(RequestMappingInfo mapping, Object handler, Method method) {
+		super.registerMapping(mapping, handler, method);
+		updateConsumesCondition(mapping, method);
+	}
+
+	@Override
+	protected void registerHandlerMethod(Object handler, Method method, RequestMappingInfo mapping) {
+		super.registerHandlerMethod(handler, method, mapping);
+		updateConsumesCondition(mapping, method);
+	}
+
+	private void updateConsumesCondition(RequestMappingInfo info, Method method) {
+		ConsumesRequestCondition condition = info.getConsumesCondition();
+		if (!condition.isEmpty()) {
+			for (Parameter parameter : method.getParameters()) {
+				MergedAnnotation<RequestBody> annot = MergedAnnotations.from(parameter).get(RequestBody.class);
+				if (annot.isPresent()) {
+					condition.setBodyRequired(annot.getBoolean("required"));
+					break;
+				}
+			}
+		}
+	}
+
 	@Override
 	protected CorsConfiguration initCorsConfiguration(Object handler, Method method, RequestMappingInfo mappingInfo) {
 		HandlerMethod handlerMethod = createHandlerMethod(handler, method);