Add route(RequestPredicate, HandlerFunction) to RouterFunctions builder

Closes gh-22701

Author: poutsma

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -140,6 +140,12 @@ public RouterFunctions.Builder OPTIONS(String pattern, RequestPredicate predicat
 		return add(RequestPredicates.OPTIONS(pattern).and(predicate), handlerFunction);
 	}
 
+	@Override
+	public RouterFunctions.Builder route(RequestPredicate predicate,
+			HandlerFunction<ServerResponse> handlerFunction) {
+		return add(RouterFunctions.route(predicate, handlerFunction));
+	}
+
 	@Override
 	public RouterFunctions.Builder resources(String pattern, Resource location) {
 		return add(RouterFunctions.resources(pattern, location));

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

@@ -477,6 +477,18 @@ public interface Builder {
 		 */
 		Builder OPTIONS(String pattern, RequestPredicate predicate, HandlerFunction<ServerResponse> handlerFunction);
 
+		/**
+		 * Adds a route to the given handler function that handles all requests that match the
+		 * given predicate.
+		 *
+		 * @param predicate the request predicate to match
+		 * @param handlerFunction the handler function to handle all requests that match the predicate
+		 * @return this builder
+		 * @since 5.2
+		 * @see RequestPredicates
+		 */
+		Builder route(RequestPredicate predicate, HandlerFunction<ServerResponse> handlerFunction);
+
 		/**
 		 * Adds the given route to this builder. Can be used to merge externally defined router
 		 * functions into this builder, or can be combined with

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/RouterFunctionBuilderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -30,6 +30,7 @@
 import org.springframework.http.MediaType;
 
 import static org.junit.Assert.*;
+import static org.springframework.web.reactive.function.server.RequestPredicates.HEAD;
 
 /**
  * @author Arjen Poutsma
@@ -41,23 +42,37 @@ public void route() {
 		RouterFunction<ServerResponse> route = RouterFunctions.route()
 				.GET("/foo", request -> ServerResponse.ok().build())
 				.POST("/", RequestPredicates.contentType(MediaType.TEXT_PLAIN), request -> ServerResponse.noContent().build())
+				.route(HEAD("/foo"), request -> ServerResponse.accepted().build())
 				.build();
-		System.out.println(route);
 
-		MockServerRequest fooRequest = MockServerRequest.builder().
+		MockServerRequest getFooRequest = MockServerRequest.builder().
 				method(HttpMethod.GET).
 				uri(URI.create("http://localhost/foo"))
 				.build();
 
-		Mono<Integer> responseMono = route.route(fooRequest)
-				.flatMap(handlerFunction -> handlerFunction.handle(fooRequest))
+		Mono<Integer> responseMono = route.route(getFooRequest)
+				.flatMap(handlerFunction -> handlerFunction.handle(getFooRequest))
 				.map(ServerResponse::statusCode)
 				.map(HttpStatus::value);
 
 		StepVerifier.create(responseMono)
 				.expectNext(200)
 				.verifyComplete();
 
+		MockServerRequest headFooRequest = MockServerRequest.builder().
+				method(HttpMethod.HEAD).
+				uri(URI.create("http://localhost/foo"))
+				.build();
+
+		responseMono = route.route(headFooRequest)
+				.flatMap(handlerFunction -> handlerFunction.handle(getFooRequest))
+				.map(ServerResponse::statusCode)
+				.map(HttpStatus::value);
+
+		StepVerifier.create(responseMono)
+				.expectNext(202)
+				.verifyComplete();
+
 		MockServerRequest barRequest = MockServerRequest.builder().
 				method(HttpMethod.POST).
 				uri(URI.create("http://localhost/"))