Prevent early bean initialization with @EnableCaching

Prior to this commmit, any configuration class holding a CacheManager
bean would be eagerly instantiated. This is because the
CacheConfiguration infrastructure requests all beans of type
CacheManager.

This commit defers the resolution of the CacheManager as late
as possible.

Issue: SPR-12336

spring-context-support/src/main/java/org/springframework/cache/jcache/interceptor/DefaultJCacheOperationSource.java

@@ -21,6 +21,7 @@ import java.util.Map;
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.cache.CacheManager;
 import org.springframework.cache.interceptor.CacheResolver;
 import org.springframework.cache.interceptor.KeyGenerator;
@@ -39,7 +40,7 @@ import org.springframework.util.Assert;
  * @since 4.1
  */
 public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSource
-		implements InitializingBean, ApplicationContextAware {
+		implements InitializingBean, SmartInitializingSingleton, ApplicationContextAware {
 
 	private CacheManager cacheManager;
 
@@ -83,7 +84,7 @@ public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSourc
 	}
 
 	public CacheResolver getCacheResolver() {
-		return this.cacheResolver;
+		return getDefaultCacheResolver();
 	}
 
 	/**
@@ -95,7 +96,7 @@ public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSourc
 	}
 
 	public CacheResolver getExceptionCacheResolver() {
-		return this.exceptionCacheResolver;
+		return getDefaultExceptionCacheResolver();
 	}
 
 	@Override
@@ -105,17 +106,13 @@ public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSourc
 
 	@Override
 	public void afterPropertiesSet() {
-		Assert.state((this.cacheResolver != null && this.exceptionCacheResolver != null)
-				|| this.cacheManager != null, "'cacheManager' is required if cache resolvers are not set.");
-		Assert.state(this.applicationContext != null, "The application context was not injected as it should.");
-
 		this.adaptedKeyGenerator = new KeyGeneratorAdapter(this, this.keyGenerator);
-		if (this.cacheResolver == null) {
-			this.cacheResolver = new SimpleCacheResolver(this.cacheManager);
-		}
-		if (this.exceptionCacheResolver == null) {
-			this.exceptionCacheResolver = new SimpleExceptionCacheResolver(this.cacheManager);
-		}
+	}
+
+	@Override
+	public void afterSingletonsInstantiated() { // Make sure those are initialized on startup
+		Assert.notNull(getDefaultCacheResolver(), "Cache resolver should have been initialized.");
+		Assert.notNull(getDefaultExceptionCacheResolver(), "Exception cache resolver should have been initialized.");
 	}
 
 	@Override
@@ -131,11 +128,17 @@ public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSourc
 
 	@Override
 	protected CacheResolver getDefaultCacheResolver() {
+		if (this.cacheResolver == null) {
+			this.cacheResolver = new SimpleCacheResolver(getCacheManager());
+		}
 		return this.cacheResolver;
 	}
 
 	@Override
 	protected CacheResolver getDefaultExceptionCacheResolver() {
+		if (this.exceptionCacheResolver == null) {
+			this.exceptionCacheResolver = new SimpleExceptionCacheResolver(getCacheManager());
+		}
 		return this.exceptionCacheResolver;
 	}
 
@@ -144,4 +147,16 @@ public class DefaultJCacheOperationSource extends AnnotationJCacheOperationSourc
 		return this.adaptedKeyGenerator;
 	}
 
+	private CacheManager getCacheManager() {
+		if (this.cacheManager == null) {
+			this.cacheManager = this.applicationContext.getBean(CacheManager.class);
+			if (this.cacheManager == null) {
+				throw new IllegalStateException("No bean of type CacheManager could be found. " +
+						"Register a CacheManager bean or remove the @EnableCaching annotation " +
+						"from your configuration.");
+			}
+		}
+		return this.cacheManager;
+	}
+
 }