Enhance AOT-Support (Issue#3171) (#3193)

replace registerBeanDefinition callback with a factoryMethod
split out a RouterFunctionHolderFactory from the Registrar class and provide its bean in the AutoConfiguration
set refresh scope on the RouterFunctionHolder bean only if RefreshScope bean in context and add warning

add runtimeHintsRegistrar to allow externalized route configuration

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2023 the original author or authors.
+ * Copyright 2013-2024 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.
@@ -28,8 +28,10 @@
 import org.springframework.boot.web.client.ClientHttpRequestFactorySettings;
 import org.springframework.boot.web.client.RestClientCustomizer;
 import org.springframework.cloud.gateway.server.mvc.common.ArgumentSupplierBeanPostProcessor;
+import org.springframework.cloud.gateway.server.mvc.config.GatewayMvcAotRuntimeHintsRegistrar;
 import org.springframework.cloud.gateway.server.mvc.config.GatewayMvcProperties;
 import org.springframework.cloud.gateway.server.mvc.config.GatewayMvcPropertiesBeanDefinitionRegistrar;
+import org.springframework.cloud.gateway.server.mvc.config.RouterFunctionHolderFactory;
 import org.springframework.cloud.gateway.server.mvc.filter.FormFilter;
 import org.springframework.cloud.gateway.server.mvc.filter.ForwardedRequestHeadersFilter;
 import org.springframework.cloud.gateway.server.mvc.filter.HttpHeadersFilter.RequestHttpHeadersFilter;
@@ -48,14 +50,23 @@
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportRuntimeHints;
+import org.springframework.core.env.Environment;
 import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.JdkClientHttpRequestFactory;
 import org.springframework.util.StringUtils;
 import org.springframework.web.client.RestClient;
 
+/**
+ * AutoConfiguration for Spring Cloud Gateway MVC server.
+ *
+ * @author Spencer Gibb
+ * @author Jürgen Wißkirchen
+ */
 @AutoConfiguration(after = { RestTemplateAutoConfiguration.class, RestClientAutoConfiguration.class })
 @ConditionalOnProperty(name = "spring.cloud.gateway.mvc.enabled", matchIfMissing = true)
 @Import(GatewayMvcPropertiesBeanDefinitionRegistrar.class)
+@ImportRuntimeHints(GatewayMvcAotRuntimeHintsRegistrar.class)
 public class GatewayServerMvcAutoConfiguration {
 
 	@Bean
@@ -64,6 +75,11 @@ public static ArgumentSupplierBeanPostProcessor argumentSupplierBeanPostProcesso
 		return new ArgumentSupplierBeanPostProcessor(publisher);
 	}
 
+	@Bean
+	public RouterFunctionHolderFactory routerFunctionHolderFactory(Environment env) {
+		return new RouterFunctionHolderFactory(env);
+	}
+
 	@Bean
 	public RestClientCustomizer gatewayRestClientCustomizer(ClientHttpRequestFactory requestFactory) {
 		return restClientBuilder -> restClientBuilder.requestFactory(requestFactory);

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

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2013-2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.gateway.server.mvc.config;
+
+import java.util.Arrays;
+import java.util.Set;
+
+import org.springframework.aot.hint.ExecutableMode;
+import org.springframework.aot.hint.MemberCategory;
+import org.springframework.aot.hint.ReflectionHints;
+import org.springframework.aot.hint.RuntimeHints;
+import org.springframework.aot.hint.RuntimeHintsRegistrar;
+import org.springframework.cloud.gateway.server.mvc.filter.AfterFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.BodyFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.Bucket4jFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.CircuitBreakerFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.FilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.LoadBalancerFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.filter.LoadBalancerHandlerSupplier;
+import org.springframework.cloud.gateway.server.mvc.filter.TokenRelayFilterFunctions;
+import org.springframework.cloud.gateway.server.mvc.handler.GatewayRouterFunctions;
+import org.springframework.cloud.gateway.server.mvc.handler.HandlerFunctions;
+import org.springframework.cloud.gateway.server.mvc.predicate.GatewayRequestPredicates;
+import org.springframework.lang.NonNull;
+import org.springframework.util.ClassUtils;
+
+/**
+ * AOT runtime hints registrar on the gateway server mvc.
+ *
+ * @author Jürgen Wißkirchen
+ */
+public class GatewayMvcAotRuntimeHintsRegistrar implements RuntimeHintsRegistrar {
+
+	private static final Set<Class<?>> FUNCTION_PROVIDERS = Set.of(HandlerFunctions.class,
+			LoadBalancerHandlerSupplier.class, FilterFunctions.class, BeforeFilterFunctions.class,
+			AfterFilterFunctions.class, TokenRelayFilterFunctions.class, BodyFilterFunctions.class,
+			CircuitBreakerFilterFunctions.class, GatewayRouterFunctions.class, LoadBalancerFilterFunctions.class,
+			GatewayRequestPredicates.class, Bucket4jFilterFunctions.class);
+
+	private static final Set<Class<?>> PROPERTIES = Set.of(FilterProperties.class, PredicateProperties.class,
+			RouteProperties.class);
+
+	@Override
+	public void registerHints(@NonNull RuntimeHints hints, ClassLoader classLoader) {
+		final ReflectionHints reflectionHints = hints.reflection();
+		FUNCTION_PROVIDERS.forEach(clazz -> addHintsForClass(reflectionHints, clazz, classLoader));
+
+		PROPERTIES.forEach(clazz -> reflectionHints.registerType(clazz, MemberCategory.PUBLIC_FIELDS,
+				MemberCategory.INVOKE_PUBLIC_METHODS, MemberCategory.INVOKE_PUBLIC_CONSTRUCTORS));
+	}
+
+	/**
+	 * Add hints for the given class. Since we need to register mostly static methods, the
+	 * annotation way with @Reflective does not work here.
+	 * @param reflectionHints the reflection hints
+	 * @param clazz the class to add hints for
+	 * @param classLoader the class loader
+	 */
+	private void addHintsForClass(ReflectionHints reflectionHints, Class<?> clazz, ClassLoader classLoader) {
+		if (!ClassUtils.isPresent(clazz.getName(), classLoader)) {
+			return; // safety net
+		}
+		Arrays.stream(clazz.getMethods())
+				.forEach(method -> reflectionHints.registerMethod(method, ExecutableMode.INVOKE));
+	}
+
+}