Add default methods to CachingConfigurer

This commit adds default methods to CachingConfigurer and
JCacheConfigurer and removes the reference to their respective support
classes as they are now irrelevant.

Closes gh-27811

spring-context/src/main/java/org/springframework/cache/annotation/CachingConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -26,8 +26,7 @@ import org.springframework.lang.Nullable;
  * Interface to be implemented by @{@link org.springframework.context.annotation.Configuration
  * Configuration} classes annotated with @{@link EnableCaching} that wish or need to
  * specify explicitly how caches are resolved and how keys are generated for annotation-driven
- * cache management. Consider extending {@link CachingConfigurerSupport}, which provides a
- * stub implementation of all interface methods.
+ * cache management.
  *
  * <p>See @{@link EnableCaching} for general examples and context; see
  * {@link #cacheManager()}, {@link #cacheResolver()} and {@link #keyGenerator()}
@@ -37,7 +36,6 @@ import org.springframework.lang.Nullable;
  * @author Stephane Nicoll
  * @since 3.1
  * @see EnableCaching
- * @see CachingConfigurerSupport
  */
 public interface CachingConfigurer {
 
@@ -64,7 +62,9 @@ public interface CachingConfigurer {
 	 * See @{@link EnableCaching} for more complete examples.
 	 */
 	@Nullable
-	CacheManager cacheManager();
+	default CacheManager cacheManager() {
+		return null;
+	}
 
 	/**
 	 * Return the {@link CacheResolver} bean to use to resolve regular caches for
@@ -89,7 +89,9 @@ public interface CachingConfigurer {
 	 * See {@link EnableCaching} for more complete examples.
 	 */
 	@Nullable
-	CacheResolver cacheResolver();
+	default CacheResolver cacheResolver() {
+		return null;
+	}
 
 	/**
 	 * Return the key generator bean to use for annotation-driven cache management.
@@ -110,7 +112,9 @@ public interface CachingConfigurer {
 	 * See @{@link EnableCaching} for more complete examples.
 	 */
 	@Nullable
-	KeyGenerator keyGenerator();
+	default KeyGenerator keyGenerator() {
+		return null;
+	}
 
 	/**
 	 * Return the {@link CacheErrorHandler} to use to handle cache-related errors.
@@ -133,6 +137,8 @@ public interface CachingConfigurer {
 	 * See @{@link EnableCaching} for more complete examples.
 	 */
 	@Nullable
-	CacheErrorHandler errorHandler();
+	default CacheErrorHandler errorHandler() {
+		return null;
+	}
 
 }