GH-3926: BeanNameGenerator for @MessagingGateway (#3927)

* GH-3926: BeanNameGenerator for @MessagingGateway

Fixes https://github.com/spring-projects/spring-integration/issues/3926

Current approach for generated bean name in the `MessagingGatewayRegistrar`
is to decapitalize simple class name, which is similar to standard `AnnotationBeanNameGenerator`

* Make logic in the `MessagingGatewayRegistrar` based on the provided `BeanNameGenerator`
* Expose an `@IntegrationComponentScan.nameGenerator()` attribute to allow to customize
default bean name generation strategy
* Introduce `IntegrationConfigUtils.annotationBeanNameGenerator()` to
take a provided `AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR` singleton
or fallback to the `AnnotationBeanNameGenerator.INSTANCE`
* Use this utility in the `IntegrationComponentScanRegistrar` if no custom strategy is provided
in the `@IntegrationComponentScan`
* Use same util from the `GatewayParser` since there is no custom naming strategy configuration
* Some other current Java level refactoring in the `IntegrationComponentScanRegistrar`
and `MessagingGatewayRegistrar`

* * Meta-annotate `@MessagingGateway` with a `@MessageEndpoint`
* Alias `@MessageEndpoint.value()` with a `@Component.value()`
* Alias `@MessagingGateway.name()` with a `@MessageEndpoint.value()`

* * Remove unused imports

* * Replace `MessagingGatewayRegistrar` parsing logic for annotation configuration
directly by the `GatewayProxyInstantiationPostProcessor` and `AnnotationGatewayProxyFactoryBean`.
* The `MessagingGatewayRegistrar` logic has been migrated back to the `GatewayParser`,
but only with an XML-relevant parts
* Change the logic of the `IntegrationComponentScanRegistrar` to rely on a `ClassPathBeanDefinitionScanner`
and its `scan()` functionality since this is all what we need to trigger a `GatewayProxyInstantiationPostProcessor`
for scanned components
* Fix `GatewayProxyInstantiationPostProcessor` to call an `afterPropertiesSet()` as well
* Add a `value()` alias attribute for the `@MessagingGateway` to satisfy a name resolution from a `@Component`
* Replace annotation chain resolution logic by new `MessagingAnnotationUtils.resolveMergedAttribute()` API
* Use `MergedAnnotations` API in the `AnnotationGatewayProxyFactoryBean` to preserve a logic for attribute
resolution from the annotation hierarchy
* Add expression resolution for attribute values in the `AnnotationGatewayProxyFactoryBean`
* Make a `GatewayInterfaceTests.CustomBeanNameGenerator` as an `AnnotationBeanNameGenerator`
extension to satisfy the test logic expectations: no custom name if explicit is present
* Clean up some doc typos after merge conflict

The fix in this commit essentially resolves some old JIRA ticket: https://jira.spring.io/browse/INT-4558

* * Remove redundant `MessagingAnnotationUtils.resolveMergedAttribute()`
* Optimize the logic in the `AnnotationGatewayProxyFactoryBean` around
annotation attributes to plain annotation - no adaptation to maps

spring-integration-core/src/test/java/org/springframework/integration/configuration/EnableIntegrationTests.java

@@ -64,6 +64,7 @@ import org.springframework.context.annotation.Lazy;
 import org.springframework.context.expression.EnvironmentAccessor;
 import org.springframework.context.expression.MapAccessor;
 import org.springframework.core.annotation.AliasFor;
+import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.core.log.LogAccessor;
 import org.springframework.core.serializer.support.SerializingConverter;
@@ -488,6 +489,10 @@ public class EnableIntegrationTests {
 
 	@Test
 	public void testMessagingGateway() throws InterruptedException {
+		String gatewayBeanName = AnnotatedElementUtils.findMergedAnnotation(TestGateway.class, Component.class).value();
+		assertThat(gatewayBeanName).isEqualTo("namedTestGateway");
+		assertThat(this.testGateway).isSameAs(this.context.getBean(gatewayBeanName));
+
 		String payload = "bar";
 		String result = this.testGateway.echo(payload);
 		assertThat(result.substring(0, payload.length())).isEqualTo(payload.toUpperCase());
@@ -1464,7 +1469,7 @@ public class EnableIntegrationTests {
 
 	}
 
-	@TestMessagingGateway
+	@TestMessagingGateway("namedTestGateway")
 	public interface TestGateway {
 
 		@Gateway(headers = @GatewayHeader(name = "calledMethod", expression = "method.name"))
@@ -1494,6 +1499,9 @@ public class EnableIntegrationTests {
 			defaultHeaders = @GatewayHeader(name = "foo", value = "FOO"))
 	public @interface TestMessagingGateway {
 
+		@AliasFor(annotation = MessagingGateway.class, attribute = "value")
+		String value() default "";
+
 		@AliasFor(annotation = MessagingGateway.class, attribute = "defaultRequestChannel")
 		String defaultRequestChannel() default "";
 

spring-integration-core/src/test/java/org/springframework/integration/enablecomponentscan/EnableComponentScanTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2022 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.
@@ -21,21 +21,21 @@ import static org.assertj.core.api.Assertions.assertThat;
 import java.util.Collection;
 import java.util.Collections;
 
-import org.junit.Test;
-import org.junit.runner.RunWith;
+import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.core.annotation.AnnotationAttributes;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.integration.annotation.IntegrationComponentScan;
 import org.springframework.integration.config.EnableIntegration;
 import org.springframework.integration.config.IntegrationComponentScanRegistrar;
 import org.springframework.integration.dsl.flows.IntegrationFlowTests;
 import org.springframework.test.annotation.DirtiesContext;
-import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -44,7 +44,7 @@ import org.springframework.util.ClassUtils;
  *
  * @since 4.0
  */
-@RunWith(SpringRunner.class)
+@SpringJUnitConfig
 @DirtiesContext
 public class EnableComponentScanTests {
 
@@ -68,13 +68,15 @@ public class EnableComponentScanTests {
 		@Override
 		public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
 				BeanDefinitionRegistry registry) {
+
 			super.registerBeanDefinitions(
 					AnnotationMetadata.introspect(IntegrationComponentScanConfiguration.class), registry);
 		}
 
 		@Override
-		protected Collection<String> getBasePackages(AnnotationMetadata importingClassMetadata,
+		protected Collection<String> getBasePackages(AnnotationAttributes importingClassMetadata,
 				BeanDefinitionRegistry registry) {
+
 			return Collections.singleton(ClassUtils.getPackageName(IntegrationFlowTests.ControlBusGateway.class));
 		}
 

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

@@ -45,8 +45,10 @@ 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;
+import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationBeanNameGenerator;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Condition;
@@ -94,6 +96,7 @@ import org.springframework.stereotype.Component;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.ActiveProfiles;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
+import org.springframework.util.ClassUtils;
 
 /**
  * @author Oleg Zhurakousky
@@ -121,11 +124,11 @@ public class GatewayInterfaceTests {
 	private NoExecGateway noExecGateway;
 
 	@Autowired
-	@Qualifier("&gatewayInterfaceTests$ExecGateway")
+	@Qualifier("&execGateway")
 	private GatewayProxyFactoryBean<?> execGatewayFB;
 
 	@Autowired
-	@Qualifier("&gatewayInterfaceTests$NoExecGateway")
+	@Qualifier("&noExecutorGateway")
 	private GatewayProxyFactoryBean<?> noExecGatewayFB;
 
 	@Autowired
@@ -642,8 +645,10 @@ public class GatewayInterfaceTests {
 	@Configuration
 	@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE,
 			classes = AutoCreateChannelService.class))
-	@IntegrationComponentScan(useDefaultFilters = false,
-			includeFilters = @ComponentScan.Filter(TestMessagingGateway.class))
+	@IntegrationComponentScan(
+			useDefaultFilters = false,
+			includeFilters = @ComponentScan.Filter(TestMessagingGateway.class),
+			nameGenerator = CustomBeanNameGenerator.class)
 	@EnableIntegration
 	@Import(ImportedGateway.class)
 	public static class TestConfig {
@@ -754,7 +759,7 @@ public class GatewayInterfaceTests {
 
 	}
 
-	@MessagingGateway(asyncExecutor = AnnotationConstants.NULL)
+	@MessagingGateway(name = "noExecutorGateway", asyncExecutor = AnnotationConstants.NULL)
 	@TestMessagingGateway
 	public interface NoExecGateway {
 
@@ -836,4 +841,20 @@ public class GatewayInterfaceTests {
 
 	}
 
+	public static class CustomBeanNameGenerator extends AnnotationBeanNameGenerator {
+
+		@Override
+		protected String buildDefaultBeanName(BeanDefinition definition) {
+			try {
+				Class<?> beanClass = ClassUtils.forName(definition.getBeanClassName(),
+						ClassUtils.getDefaultClassLoader());
+				return ClassUtils.getShortNameAsProperty(beanClass);
+			}
+			catch (ClassNotFoundException ex) {
+				throw new IllegalStateException(ex);
+			}
+		}
+
+	}
+
 }