Implement retrieve(key) and retrieve(key, :Supplier<CompletableFuture<T>>) operations in Cache.

Closes spring-projects#2650

Author: jxblum

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

@@ -24,6 +24,8 @@
 import java.util.Map.Entry;
 import java.util.StringJoiner;
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Supplier;
 
 import org.springframework.cache.Cache;
 import org.springframework.cache.support.AbstractValueAdaptingCache;
@@ -281,6 +283,16 @@ protected Object preProcessCacheValue(@Nullable Object value) {
 		return value != null ? value : isAllowNullValues() ? NullValue.INSTANCE : null;
 	}
 
+	@Override
+	public CompletableFuture<?> retrieve(Object key) {
+		return super.retrieve(key);
+	}
+
+	@Override
+	public <T> CompletableFuture<T> retrieve(Object key, Supplier<CompletableFuture<T>> valueLoader) {
+		return super.retrieve(key, valueLoader);
+	}
+
 	/**
 	 * Serialize the given {@link String cache key}.
 	 *