For lb: scheme, put associated filters last.

This makes sure the lb filter runs after path modifying filters like stripPrefix.

See gh-3443

Author: spencergibb

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/loadbalancer.adoc

@@ -43,6 +43,8 @@ spring:
           - Path=/api/**
 ----
 
+WARNING: If using the `lb()` filter, it needs to be after any filter that manipulates the path such as `setPath()` or `stripPrefix()`, otherwise the resulting url could be incorrect. The `lb:` scheme handler in configuration, automatically puts the filter in the highest precedence order.
+
 NOTE: By default, when a service instance cannot be found by the `ReactorLoadBalancer`, a `503` is returned.
 // TODO: implement use404
 // You can configure the gateway to return a `404` by setting `spring.cloud.gateway.loadbalancer.use404=true`.

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/prefixpath.adoc

@@ -33,7 +33,7 @@ class RouteConfiguration {
     public RouterFunction<ServerResponse> gatewayRouterFunctionsPrefixPath() {
 		return route("prefixpath_route")
 				.GET("/**", http("https://example.org"))
-					.before("/mypath")
+					.before(prefixPath("/mypath"))
 					.build();
     }
 }
@@ -42,3 +42,4 @@ class RouteConfiguration {
 This prefixes `/mypath` to the path of all matching requests.
 So a request to `/hello` is sent to `/mypath/hello`.
 
+WARNING: If using the `lb()` filter, it needs to be after the `prefixPath()` filter, otherwise the resulting url could be incorrect. The `lb:` scheme handler in configuration, automatically puts the filter in the highest precedence order.

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/rewritepath.adoc

@@ -43,3 +43,4 @@ class RouteConfiguration {
 
 For a request path of `/red/blue`, this sets the path to `/blue` before making the downstream request. Note that in `application.yml` the `$` should be replaced with `$\` because of the YAML specification.
 
+WARNING: If using the `lb()` filter, it needs to be after the `rewritePath()` filter, otherwise the resulting url could be incorrect. The `lb:` scheme handler in configuration, automatically puts the filter in the highest precedence order.

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/setpath.adoc

@@ -45,3 +45,4 @@ class RouteConfiguration {
 
 For a request path of `/red/blue`, this sets the path to `/blue` before making the downstream request.
 
+WARNING: If using the `lb()` filter, it needs to be after the `setPath()` filter, otherwise the resulting url could be incorrect. The `lb:` scheme handler in configuration, automatically puts the filter in the highest precedence order.

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/stripprefix.adoc

@@ -43,3 +43,4 @@ class RouteConfiguration {
 
 When a request is made through the gateway to `/name/blue/red`, the request made to `nameservice` looks like `https://nameservice/red`.
 
+WARNING: If using the `lb()` filter, it needs to be after the `stripPrefix()` filter, otherwise the resulting url could be incorrect. The `lb:` scheme handler in configuration, automatically puts the filter in the highest precedence order.

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/config/RouterFunctionHolderFactory.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.gateway.server.mvc.config;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
@@ -178,12 +179,15 @@ private RouterFunction getRouterFunction(RouteProperties routeProperties, String
 		NormalizedOperationMethod normalizedOpMethod = handlerOperationMethod.get();
 		Object response = invokeOperation(normalizedOpMethod, normalizedOpMethod.getNormalizedArgs());
 		HandlerFunction<ServerResponse> handlerFunction = null;
+
+		// filters added by HandlerDiscoverer need to go last, so save them
+		List<HandlerFilterFunction<ServerResponse, ServerResponse>> handlerFilterFunctionFilters = new ArrayList<>();
 		if (response instanceof HandlerFunction<?>) {
 			handlerFunction = (HandlerFunction<ServerResponse>) response;
 		}
 		else if (response instanceof HandlerDiscoverer.Result result) {
 			handlerFunction = result.getHandlerFunction();
-			result.getFilters().forEach(builder::filter);
+			handlerFilterFunctionFilters.addAll(result.getFilters());
 		}
 		if (handlerFunction == null) {
 			throw new IllegalStateException(
@@ -221,6 +225,9 @@ else if (response instanceof HandlerDiscoverer.Result result) {
 			translate(filterOperations, filterProperties.getName(), args, HandlerFilterFunction.class, builder::filter);
 		});
 
+		// HandlerDiscoverer filters need higher priority, so put them last
+		handlerFilterFunctionFilters.forEach(builder::filter);
+
 		builder.withAttribute(MvcUtils.GATEWAY_ROUTE_ID_ATTR, routeId);
 
 		return builder.build();

spring-cloud-gateway-server-mvc/src/test/java/org/springframework/cloud/gateway/server/mvc/config/GatewayMvcPropertiesBeanDefinitionRegistrarTests.java

@@ -122,7 +122,7 @@ public void route(RequestPredicate predicate, HandlerFunction<?> handlerFunction
 				predicate.accept(new AbstractRequestPredicatesVisitor() {
 					@Override
 					public void path(String pattern) {
-						assertThat(pattern).isEqualTo("/anything/listRoute3");
+						assertThat(pattern).isEqualTo("/extra/anything/listRoute3");
 					}
 
 					@Override
@@ -181,7 +181,7 @@ public void configuredRouteWorks() {
 	@SuppressWarnings("unchecked")
 	public void lbRouteWorks() {
 		restClient.get()
-			.uri("/anything/listRoute3")
+			.uri("/extra/anything/listRoute3")
 			.header("MyHeaderName", "MyHeaderVal")
 			.exchange()
 			.expectStatus()

spring-cloud-gateway-server-mvc/src/test/resources/application-propertiesbeandefinitionregistrartests.yml

@@ -38,9 +38,12 @@ spring.cloud.gateway.mvc:
     - id: listRoute3
       uri: lb://httpbin
       predicates:
-        - Path=/anything/listRoute3
+        - Path=/extra/anything/listRoute3
         - Header=MyHeaderName,MyHeader.*
       filters:
+        - name: StripPrefix
+          args:
+            parts: 1
         - name: AddRequestHeader
           args:
             name: X-Test