Add route(RequestPredicate, HandlerFunction) to RouterFunctions builder

Closes gh-22701

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.HttpStatus;
 import org.springframework.http.MediaType;
 
 import static org.junit.Assert.*;
+import static org.springframework.web.reactive.function.server.RequestPredicates.HEAD;
 
 /**
  * @author Arjen Poutsma
@@ -41,16 +42,16 @@ public class RouterFunctionBuilderTests {
 		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);
 
@@ -58,6 +59,20 @@ public class RouterFunctionBuilderTests {
 				.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/"))