Avoid early init of CacheManager

This commit restructures the Cache auto-configuration to avoid an early
init on CacheManager (and potentially all its infrastructure). Rather
than adding a dependency on the validator bean, this commit relies on
the fact CacheAspectSupport checks if a CacheManager is available in the
afterSingletonsInstantiated callback. In this case, a simple bean with
a postconstruct callback is enough.

Closes gh-13038

Author: snicoll

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/CacheAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -18,14 +18,8 @@
 
 import java.util.List;
 
-import javax.annotation.PostConstruct;
-
-import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.ObjectProvider;
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.beans.factory.config.BeanDefinition;
-import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
-import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
@@ -46,7 +40,6 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.ImportSelector;
-import org.springframework.context.annotation.Role;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.orm.jpa.AbstractEntityManagerFactoryBean;
 import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
@@ -73,8 +66,6 @@
 @Import(CacheConfigurationImportSelector.class)
 public class CacheAutoConfiguration {
 
-	static final String VALIDATOR_BEAN_NAME = "cacheAutoConfigurationValidator";
-
 	@Bean
 	@ConditionalOnMissingBean
 	public CacheManagerCustomizers cacheManagerCustomizers(
@@ -83,14 +74,10 @@ public CacheManagerCustomizers cacheManagerCustomizers(
 	}
 
 	@Bean
-	@Role(BeanDefinition.ROLE_INFRASTRUCTURE)
-	public static CacheManagerValidatorPostProcessor cacheAutoConfigurationValidatorPostProcessor() {
-		return new CacheManagerValidatorPostProcessor();
-	}
-
-	@Bean(name = VALIDATOR_BEAN_NAME)
-	public CacheManagerValidator cacheAutoConfigurationValidator() {
-		return new CacheManagerValidator();
+	public CacheManagerValidator cacheAutoConfigurationValidator(
+			CacheProperties cacheProperties,
+			ObjectProvider<CacheManager> cacheManager) {
+		return new CacheManagerValidator(cacheProperties, cacheManager);
 	}
 
 	@Configuration
@@ -105,50 +92,25 @@ public CacheManagerJpaDependencyConfiguration() {
 
 	}
 
-	/**
-	 * {@link BeanFactoryPostProcessor} to ensure that the {@link CacheManagerValidator}
-	 * is triggered before {@link CacheAspectSupport} but without causing early
-	 * instantiation.
-	 */
-	static class CacheManagerValidatorPostProcessor implements BeanFactoryPostProcessor {
-
-		@Override
-		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
-				throws BeansException {
-			for (String name : beanFactory.getBeanNamesForType(CacheAspectSupport.class,
-					false, false)) {
-				BeanDefinition definition = beanFactory.getBeanDefinition(name);
-				definition.setDependsOn(
-						append(definition.getDependsOn(), VALIDATOR_BEAN_NAME));
-			}
-		}
-
-		private String[] append(String[] array, String value) {
-			String[] result = new String[array != null ? array.length + 1 : 1];
-			if (array != null) {
-				System.arraycopy(array, 0, result, 0, array.length);
-			}
-			result[result.length - 1] = value;
-			return result;
-		}
-
-	}
-
 	/**
 	 * Bean used to validate that a CacheManager exists and provide a more meaningful
 	 * exception.
 	 */
-	static class CacheManagerValidator {
+	static class CacheManagerValidator implements InitializingBean {
+
+		private final CacheProperties cacheProperties;
 
-		@Autowired
-		private CacheProperties cacheProperties;
+		private final ObjectProvider<CacheManager> cacheManager;
 
-		@Autowired(required = false)
-		private CacheManager cacheManager;
+		CacheManagerValidator(CacheProperties cacheProperties,
+				ObjectProvider<CacheManager> cacheManager) {
+			this.cacheProperties = cacheProperties;
+			this.cacheManager = cacheManager;
+		}
 
-		@PostConstruct
-		public void checkHasCacheManager() {
-			Assert.notNull(this.cacheManager,
+		@Override
+		public void afterPropertiesSet() {
+			Assert.notNull(this.cacheManager.getIfAvailable(),
 					"No cache manager could "
 							+ "be auto-configured, check your configuration (caching "
 							+ "type is '" + this.cacheProperties.getType() + "')");

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/cache/CacheAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -51,9 +51,11 @@
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import org.springframework.beans.BeansException;
 import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.boot.autoconfigure.cache.support.MockCachingProvider;
 import org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration;
 import org.springframework.boot.test.util.EnvironmentTestUtils;
@@ -770,6 +772,17 @@ public void caffeineCacheExplicitWithSpecString() {
 		validateCaffeineCacheWithStats();
 	}
 
+	@Test
+	public void autoConfiguredCacheManagerCanBeSwapped() {
+		load(CacheManagerPostProcessorConfiguration.class, "spring.cache.type=caffeine");
+		validateCacheManager(SimpleCacheManager.class);
+		CacheManagerPostProcessor postProcessor = this.context.getBean(
+				CacheManagerPostProcessor.class);
+		assertThat(postProcessor.cacheManagers).hasSize(1);
+		assertThat(postProcessor.cacheManagers.get(0))
+				.isInstanceOf(CaffeineCacheManager.class);
+	}
+
 	private void validateCaffeineCacheWithStats() {
 		CaffeineCacheManager cacheManager = validateCacheManager(
 				CaffeineCacheManager.class);
@@ -1164,4 +1177,37 @@ public void customize(T cacheManager) {
 
 	}
 
+	@Configuration
+	@EnableCaching
+	static class CacheManagerPostProcessorConfiguration {
+
+		@Bean
+		public static BeanPostProcessor cacheManagerBeanPostProcessor() {
+			return new CacheManagerPostProcessor();
+		}
+
+	}
+
+	private static class CacheManagerPostProcessor implements BeanPostProcessor {
+
+		private final List<CacheManager> cacheManagers = new ArrayList<CacheManager>();
+
+		@Override
+		public Object postProcessBeforeInitialization(Object bean,
+				String beanName) throws BeansException {
+			return bean;
+		}
+
+		@Override
+		public Object postProcessAfterInitialization(Object bean,
+				String beanName) throws BeansException {
+			if (bean instanceof CacheManager) {
+				this.cacheManagers.add((CacheManager) bean);
+				return new SimpleCacheManager();
+			}
+			return bean;
+		}
+
+	}
+
 }