Fix APC registration for @EnableTransactionManagement

Prior to this change, @EnableTransactionManagement (via the
ProxyTransactionManagementConfiguration class) did not properly
register its auto-proxy creator through the usual AopConfigUtils
methods.  It was trying to register the APC as a normal @Bean method,
but this causes issues (SPR-8494) with the logic in
AopConfigUtils#registerOrEscalateApcAsRequired, which expects the APC
bean definition to have a beanClassName property.  When the APC is
registered via a @Bean definition, it is actually a
factoryBean/factoryMethod situation with no directly resolvable
beanClass/beanClassName.

To solve this problem, ImportSelector#selectImports has been refactored
to accept an ImportSelector.Context instance. This object contains the
AnnotationMetadata of the importing class as well as the enclosing
BeanDefinitionRegistry to allow for the kind of conditional bean
registration necessary here. In this case, the bean definition that
must be registered conditionally is that of the auto-proxy creator.
It should only be registered if AdviceMode == PROXY, and thus the
ImportSelector is an appropriate place to make this happen.  It must
happen as a BeanDefinition (rather than a @Bean method) for
compatibility with AopConfigUtils, and working with the
BeanDefinitionRegistry API allows for that. This change does mean that
in certain cases like this one, #selectImports has container modifying
side effects. Documentation has been updated to reflect.

Issue: SPR-8411, SPR-8494

org.springframework.integration-tests/src/test/java/org/springframework/transaction/annotation/EnableTransactionManagementIntegrationTests.java

@@ -22,6 +22,7 @@ import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
@@ -32,9 +33,14 @@ import org.junit.Test;
 import org.springframework.aop.Advisor;
 import org.springframework.aop.framework.Advised;
 import org.springframework.aop.support.AopUtils;
+import org.springframework.cache.Cache;
+import org.springframework.cache.CacheManager;
+import org.springframework.cache.concurrent.ConcurrentMapCache;
+import org.springframework.cache.support.SimpleCacheManager;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.ImportResource;
 import org.springframework.context.config.AdviceMode;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
@@ -152,6 +158,38 @@ public class EnableTransactionManagementIntegrationTests {
 		assertThat(txManager2.rollbacks, equalTo(0));
 	}
 
+	@Test
+	public void apcEscalation() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(EnableTxAndCachingConfig.class);
+		ctx.refresh();
+	}
+
+
+	@Configuration
+	@EnableTransactionManagement
+	@ImportResource("org/springframework/transaction/annotation/enable-caching.xml")
+	static class EnableTxAndCachingConfig {
+		@Bean
+		public PlatformTransactionManager txManager() {
+			return new CallCountingTransactionManager();
+		}
+
+		@Bean
+		public FooRepository fooRepository() {
+			return new DummyFooRepository();
+		}
+
+		@Bean
+		public CacheManager cacheManager() {
+			SimpleCacheManager mgr = new SimpleCacheManager();
+			ArrayList<Cache> caches = new ArrayList<Cache>();
+			caches.add(new ConcurrentMapCache());
+			mgr.setCaches(caches);
+			return mgr;
+		}
+	}
+
 
 	@Configuration
 	@EnableTransactionManagement

org.springframework.integration-tests/src/test/resources/org/springframework/transaction/annotation/enable-caching.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:cache="http://www.springframework.org/schema/cache"
+	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+		http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd">
+
+	<cache:annotation-driven/>
+
+</beans>