Improve RedisCacheManagerBuilder to expose applied RedisCacheConfiguration.

Now it is possible to construct a new, custom default RedisCacheConfiguration from an existing, default RedisCacheConfiguration.

This is useful in a Spring Boot context using the RedisCacheManagerBuilderCustomizer and acquiring access to the default RedisCacheConfiguration, which likely originated from Spring Boot Redis CacheProperties.

Resolves #2583

src/main/java/org/springframework/data/redis/cache/RedisCacheManager.java

@@ -41,6 +41,7 @@ import org.springframework.util.Assert;
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Yanming Zhou
  * @since 2.0
  * @see RedisCacheConfiguration
  * @see RedisCacheWriter
@@ -336,6 +337,15 @@ public class RedisCacheManager extends AbstractTransactionSupportingCacheManager
 			return this;
 		}
 
+		/**
+		 * Returns applied {@link RedisCacheConfiguration}, allow customization base on it.
+		 *
+		 * @return applied {@link RedisCacheConfiguration}.
+		 */
+		public RedisCacheConfiguration cacheDefaults() {
+			return this.defaultCacheConfiguration;
+		}
+
 		/**
 		 * Configure a {@link RedisCacheWriter}.
 		 *