Fix parameter bug of handler inside the filterFunction DSL

Co-authored-by: hojongs <hojong.jjh@gmail.com>
Co-authored-by: bjh970913 <bjh970913@gmail.com>

Closes gh-26838

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDsl.kt

@@ -531,8 +531,8 @@ class CoRouterFunctionDsl internal constructor (private val init: (CoRouterFunct
 	fun filter(filterFunction: suspend (ServerRequest, suspend (ServerRequest) -> ServerResponse) -> ServerResponse) {
 		builder.filter { serverRequest, handlerFunction ->
 			mono(Dispatchers.Unconfined) {
-				filterFunction(serverRequest) {
-					handlerFunction.handle(serverRequest).awaitSingle()
+				filterFunction(serverRequest) { handlerRequest ->
+					handlerFunction.handle(handlerRequest).awaitSingle()
 				}
 			}
 		}

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDslTests.kt

@@ -152,6 +152,16 @@ class CoRouterFunctionDslTests {
 		}
 	}
 
+	@Test
+	fun filtering() {
+		val mockRequest = get("https://example.com/filter").build()
+		val request = DefaultServerRequest(MockServerWebExchange.from(mockRequest), emptyList())
+		StepVerifier.create(sampleRouter().route(request).flatMap { it.handle(request) })
+			.expectNextMatches { response ->
+				response.headers().getFirst("foo") == "bar"
+			}
+			.verifyComplete()
+	}
 
 	private fun sampleRouter() = coRouter {
 		(GET("/foo/") or GET("/foos/")) { req -> handle(req) }
@@ -186,6 +196,18 @@ class CoRouterFunctionDslTests {
 		path("/baz", ::handle)
 		GET("/rendering") { RenderingResponse.create("index").buildAndAwait() }
 		add(otherRouter)
+		add(filterRouter)
+	}
+
+	private val filterRouter = coRouter {
+		"/filter" { request ->
+			ok().header("foo", request.headers().firstHeader("foo")).buildAndAwait()
+		}
+
+		filter { request, next ->
+			val newRequest = ServerRequest.from(request).apply { header("foo", "bar") }.build()
+			next(newRequest)
+		}
 	}
 
 	private val otherRouter = router {

spring-webmvc/src/main/kotlin/org/springframework/web/servlet/function/RouterFunctionDsl.kt

@@ -649,8 +649,8 @@ class RouterFunctionDsl internal constructor (private val init: (RouterFunctionD
 	 */
 	fun filter(filterFunction: (ServerRequest, (ServerRequest) -> ServerResponse) -> ServerResponse) {
 		builder.filter { request, next ->
-			filterFunction(request) {
-				next.handle(request)
+			filterFunction(request) { handlerRequest ->
+				next.handle(handlerRequest)
 			}
 		}
 	}

spring-webmvc/src/test/kotlin/org/springframework/web/servlet/function/RouterFunctionDslTests.kt

@@ -127,6 +127,13 @@ class RouterFunctionDslTests {
 		}
 	}
 
+	@Test
+	fun filtering() {
+		val servletRequest = PathPatternsTestUtils.initRequest("GET", "/filter", true)
+		val request = DefaultServerRequest(servletRequest, emptyList())
+		assertThat(sampleRouter().route(request).get().handle(request).headers().getFirst("foo")).isEqualTo("bar")
+	}
+
 	private fun sampleRouter() = router {
 		(GET("/foo/") or GET("/foos/")) { req -> handle(req) }
 		"/api".nest {
@@ -160,6 +167,18 @@ class RouterFunctionDslTests {
 		path("/baz", ::handle)
 		GET("/rendering") { RenderingResponse.create("index").build() }
 		add(otherRouter)
+		add(filterRouter)
+	}
+
+	private val filterRouter = router {
+		"/filter" { request ->
+			ok().header("foo", request.headers().firstHeader("foo")).build()
+		}
+
+		filter { request, next ->
+			val newRequest = ServerRequest.from(request).apply { header("foo", "bar") }.build()
+			next(newRequest)
+		}
 	}
 
 	private val otherRouter = router {