Add route(RequestPredicate, HandlerFunction) to RouterFunctions builder

Closes gh-22701

Author: poutsma

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RouterFunctionBuilder.java

@@ -132,6 +132,12 @@ public RouterFunctions.Builder OPTIONS(String pattern, HandlerFunction<ServerRes
 		return add(RequestPredicates.OPTIONS(pattern), handlerFunction);
 	}
 
+	@Override
+	public RouterFunctions.Builder route(RequestPredicate predicate,
+			HandlerFunction<ServerResponse> handlerFunction) {
+		return add(RouterFunctions.route(predicate, handlerFunction));
+	}
+
 	@Override
 	public RouterFunctions.Builder OPTIONS(String pattern, RequestPredicate predicate,
 			HandlerFunction<ServerResponse> handlerFunction) {

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RouterFunctions.java

@@ -349,6 +349,17 @@ public interface Builder {
 		 */
 		Builder OPTIONS(String pattern, 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
+		 * @see RequestPredicates
+		 */
+		Builder route(RequestPredicate predicate, HandlerFunction<ServerResponse> handlerFunction);
+
 		/**
 		 * Adds a route to the given handler function that handles all HTTP {@code OPTIONS} requests
 		 * that match the given pattern and predicate.

spring-webmvc/src/test/java/org/springframework/web/servlet/function/RouterFunctionBuilderTests.java

@@ -29,6 +29,7 @@
 
 import static java.util.Collections.emptyList;
 import static org.junit.Assert.*;
+import static org.springframework.web.servlet.function.RequestPredicates.HEAD;
 
 /**
  * @author Arjen Poutsma
@@ -41,17 +42,27 @@ public void 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();
 
 		MockHttpServletRequest servletRequest = new MockHttpServletRequest("GET", "/foo");
-		ServerRequest fooRequest = new DefaultServerRequest(servletRequest, emptyList());
+		ServerRequest getFooRequest = new DefaultServerRequest(servletRequest, emptyList());
 
-		Optional<Integer> responseStatus = route.route(fooRequest)
-				.map(handlerFunction -> handle(handlerFunction, fooRequest))
+		Optional<Integer> responseStatus = route.route(getFooRequest)
+				.map(handlerFunction -> handle(handlerFunction, getFooRequest))
 				.map(ServerResponse::statusCode)
 				.map(HttpStatus::value);
 		assertEquals(200, responseStatus.get().intValue());
 
+		servletRequest = new MockHttpServletRequest("HEAD", "/foo");
+		ServerRequest headFooRequest = new DefaultServerRequest(servletRequest, emptyList());
+
+		responseStatus = route.route(headFooRequest)
+				.map(handlerFunction -> handle(handlerFunction, getFooRequest))
+				.map(ServerResponse::statusCode)
+				.map(HttpStatus::value);
+		assertEquals(202, responseStatus.get().intValue());
+
 		servletRequest = new MockHttpServletRequest("POST", "/");
 		servletRequest.setContentType("text/plain");
 		ServerRequest barRequest = new DefaultServerRequest(servletRequest, emptyList());