GH-3923: Add @MessagingGateway @Import support (#3929)

* GH-3923: Add @MessagingGateway @Import support

Fixes https://github.com/spring-projects/spring-integration/issues/3923

Currently, the `@MessagingGateway` interfaces can be scanned or created
explicitly as `@Bean` definition for `AnnotationGatewayProxyFactoryBean`

* Implement a `GatewayProxyBeanDefinitionPostProcessor` which is invoked
before instantiation attempt on the `BeanDefinition`
* Verify `@Import` for `@MessagingGateway` interface in the `GatewayInterfaceTests`

* Remove supplier for `GatewayProxyInstantiationPostProcessor` bean definition

Co-authored-by: Gary Russell <grussell@vmware.com>

* * Fix bean definition signature

Co-authored-by: Gary Russell <grussell@vmware.com>

spring-integration-core/src/main/java/org/springframework/integration/config/GatewayProxyInstantiationPostProcessor.java

@@ -0,0 +1,75 @@
+/*
+ * 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.config;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.annotation.AnnotatedGenericBeanDefinition;
+import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
+import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.integration.annotation.MessagingGateway;
+import org.springframework.integration.gateway.AnnotationGatewayProxyFactoryBean;
+
+/**
+ * The {@link InstantiationAwareBeanPostProcessor} to wrap beans for {@link MessagingGateway}
+ * into {@link AnnotationGatewayProxyFactoryBean}.
+ *
+ * @author Artem Bilan
+ *
+ * @since 6.0
+ *
+ * @see AnnotationGatewayProxyFactoryBean
+ */
+class GatewayProxyInstantiationPostProcessor implements
+		InstantiationAwareBeanPostProcessor, ApplicationContextAware {
+
+	private final BeanDefinitionRegistry registry;
+
+	private ApplicationContext applicationContext;
+
+	GatewayProxyInstantiationPostProcessor(BeanDefinitionRegistry registry) {
+		this.registry = registry;
+	}
+
+	@Override
+	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
+		this.applicationContext = applicationContext;
+	}
+
+	@Override
+	public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
+		if (beanClass.isInterface()
+				&& AnnotatedElementUtils.hasAnnotation(beanClass, MessagingGateway.class)
+				&& this.registry.getBeanDefinition(beanName) instanceof AnnotatedGenericBeanDefinition) {
+
+			AnnotationGatewayProxyFactoryBean<?> gatewayProxyFactoryBean =
+					new AnnotationGatewayProxyFactoryBean<>(beanClass);
+			gatewayProxyFactoryBean.setApplicationContext(this.applicationContext);
+			gatewayProxyFactoryBean.setBeanFactory(this.applicationContext.getAutowireCapableBeanFactory());
+			ClassLoader classLoader = this.applicationContext.getClassLoader();
+			if (classLoader != null) {
+				gatewayProxyFactoryBean.setBeanClassLoader(classLoader);
+			}
+			gatewayProxyFactoryBean.setBeanName(beanName);
+			return gatewayProxyFactoryBean;
+		}
+		return null;
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/config/IntegrationRegistrar.java

@@ -63,6 +63,7 @@ public class IntegrationRegistrar implements ImportBeanDefinitionRegistrar {
 		if (importingClassMetadata != null) {
 			registerMessagingAnnotationPostProcessors(registry);
 		}
+		registerGatewayProxyInstantiationPostProcessor(registry);
 	}
 
 	/**
@@ -116,4 +117,15 @@ public class IntegrationRegistrar implements ImportBeanDefinitionRegistrar {
 		}
 	}
 
+	private void registerGatewayProxyInstantiationPostProcessor(BeanDefinitionRegistry registry) {
+		if (!registry.containsBeanDefinition("gatewayProxyBeanDefinitionPostProcessor")) {
+			BeanDefinitionBuilder builder =
+					BeanDefinitionBuilder.genericBeanDefinition(GatewayProxyInstantiationPostProcessor.class)
+							.addConstructorArgValue(registry)
+							.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+
+			registry.registerBeanDefinition("gatewayProxyBeanDefinitionPostProcessor", builder.getBeanDefinition());
+		}
+	}
+
 }

spring-integration-core/src/test/java/org/springframework/integration/gateway/GatewayInterfaceTests.java

@@ -41,6 +41,7 @@ import org.mockito.ArgumentCaptor;
 import org.mockito.Mockito;
 
 import org.springframework.aop.support.AopUtils;
+import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
@@ -53,6 +54,7 @@ import org.springframework.context.annotation.ConditionContext;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.FilterType;
+import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Primary;
 import org.springframework.context.annotation.Profile;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
@@ -553,6 +555,26 @@ public class GatewayInterfaceTests {
 		((SubscribableChannel) this.errorChannel).unsubscribe(messageHandler);
 	}
 
+	@Autowired
+	ImportedGateway importedGateway;
+
+	@Test
+	void importedGatewayIsProxied() {
+		assertThat(AopUtils.isAopProxy(this.importedGateway)).isTrue();
+
+		AnnotationGatewayProxyFactoryBean<?> gatewayProxyFactoryBean =
+				this.beanFactory.getBean(BeanFactory.FACTORY_BEAN_PREFIX + ImportedGateway.class.getName(),
+						AnnotationGatewayProxyFactoryBean.class);
+
+		assertThat(gatewayProxyFactoryBean.getObjectType()).isEqualTo(ImportedGateway.class);
+		assertThat(gatewayProxyFactoryBean.getGateways().keySet())
+				.hasSize(1)
+				.extracting("name")
+				.contains("handle");
+
+		assertThat(gatewayProxyFactoryBean.getComponentName()).isEqualTo(ImportedGateway.class.getName());
+	}
+
 	public interface Foo {
 
 		@Gateway(requestChannel = "requestChannelFoo")
@@ -623,6 +645,7 @@ public class GatewayInterfaceTests {
 	@IntegrationComponentScan(useDefaultFilters = false,
 			includeFilters = @ComponentScan.Filter(TestMessagingGateway.class))
 	@EnableIntegration
+	@Import(ImportedGateway.class)
 	public static class TestConfig {
 
 		@Bean(name = IntegrationContextUtils.INTEGRATION_GLOBAL_PROPERTIES_BEAN_NAME)
@@ -756,6 +779,13 @@ public class GatewayInterfaceTests {
 
 	}
 
+	@MessagingGateway
+	public interface ImportedGateway {
+
+		String handle(String payload);
+
+	}
+
 	@MessagingGateway(defaultRequestChannel = "errorChannel")
 	@TestMessagingGateway
 	public interface IgnoredHeaderGateway {

src/reference/asciidoc/gateway.adoc

@@ -319,6 +319,9 @@ Along with the `@MessagingGateway` annotation you can mark a service interface w
 
 Starting with version 6.0, an interface with the `@MessagingGateway` can also be marked with a `@Primary` annotation for respective configuration logic as its possible with any Spring `@Component` definition.
 
+Starting with version 6.0, `@MessagingGateway` interfaces can be used in the standard Spring `@Import` configuration.
+This may be used as an alternative to the  `@IntegrationComponentScan` or manual `AnnotationGatewayProxyFactoryBean` bean definitions.
+
 NOTE: If you have no XML configuration, the `@EnableIntegration` annotation is required on at least one `@Configuration` class.
 See <<./overview.adoc#configuration-enable-integration,Configuration and `@EnableIntegration`>> for more information.
 

src/reference/asciidoc/whats-new.adoc

@@ -114,6 +114,8 @@ The Messaging Gateway interface method can now return `Future<Void>` and `Mono<V
 
 Alongside with a `@MessagingGateway` annotation the interface can also be marked with a `@Primary`.
 
+`@MessagingGateway` interfaces can now be `@Import`ed into a configuration.
+
 See <<./gateway.adoc#gateway, Messaging Gateway>> for more information.
 
 The `integrationGlobalProperties` bean is now declared by the framework as an instance of `org.springframework.integration.context.IntegrationProperties` instead of the previously deprecated `java.util.Properties`.