GH-3903: Improve AOT for gateway proxy beans (#3904)

* GH-3903: Improve AOT for gateway proxy beans

Fixes #3903

* Fix `MessagingGatewayRegistrar` to set a `targetType` on the bean definition
instead of `FactoryBean.OBJECT_TYPE_ATTRIBUTE`
* Rework `GatewayProxyBeanRegistrationAotProcessor` to the
`GatewayProxyInitializationAotProcessor implements BeanFactoryInitializationAotProcessor`
to avoid custom code generation
* Remove tests which rely on the `FactoryBean.OBJECT_TYPE_ATTRIBUTE`

* * Add `setBeanClass(GatewayProxyFactoryBean.class)` to satisfy Spring container expectations

* * Rework `GatewayProxyInitializationAotProcessor` to deal with generics
we are exposing now on the `ProxyFactoryBean`

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/aot/GatewayProxyBeanRegistrationAotProcessor.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2022 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.integration.aot;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.springframework.aop.framework.AopProxyUtils;
+import org.springframework.aop.framework.ProxyFactoryBean;
+import org.springframework.aot.hint.ProxyHints;
+import org.springframework.beans.factory.aot.BeanFactoryInitializationAotContribution;
+import org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.RegisteredBean;
+import org.springframework.integration.gateway.GatewayProxyFactoryBean;
+import org.springframework.integration.gateway.RequestReplyExchanger;
+
+/**
+ * A {@link BeanFactoryInitializationAotProcessor} for registering proxy interfaces
+ * of the {@link GatewayProxyFactoryBean} beans.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.0
+ */
+class GatewayProxyInitializationAotProcessor implements BeanFactoryInitializationAotProcessor {
+
+	@Override
+	public BeanFactoryInitializationAotContribution processAheadOfTime(ConfigurableListableBeanFactory beanFactory) {
+		List<? extends Class<?>> gatewayProxyInterfaces =
+				Arrays.stream(beanFactory.getBeanDefinitionNames())
+						.map((beanName) -> RegisteredBean.of(beanFactory, beanName))
+						.filter((bean) -> ProxyFactoryBean.class.isAssignableFrom(bean.getBeanClass()))
+						.map((bean) -> bean.getBeanType().getGeneric(0).resolve(RequestReplyExchanger.class))
+						.toList();
+
+		return (generationContext, beanFactoryInitializationCode) -> {
+			ProxyHints proxyHints = generationContext.getRuntimeHints().proxies();
+			gatewayProxyInterfaces.forEach((gatewayInterface) ->
+					proxyHints.registerJdkProxy(AopProxyUtils.completeJdkProxyInterfaces(gatewayInterface)));
+		};
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/aot/GatewayProxyInitializationAotProcessor.java

@@ -1,3 +1,3 @@
 org.springframework.aot.hint.RuntimeHintsRegistrar=org.springframework.integration.aot.CoreRuntimeHints
-org.springframework.beans.factory.aot.BeanRegistrationAotProcessor=org.springframework.integration.aot.GatewayProxyBeanRegistrationAotProcessor
+org.springframework.beans.factory.aot.BeanFactoryInitializationAotProcessor=org.springframework.integration.aot.GatewayProxyInitializationAotProcessor
 org.springframework.beans.factory.aot.BeanRegistrationExcludeFilter=org.springframework.integration.aot.IntegrationBeanRegistrationExcludeFilter