DATAREDIS-635 - Polishing.

Update Javadoc and format code a bit.

Original Pull Request: #296

src/main/java/org/springframework/data/redis/connection/jedis/JedisClusterKeyCommands.java

@@ -171,10 +171,18 @@ class JedisClusterKeyCommands implements RedisKeyCommands {
 		throw new InvalidDataAccessApiUsageException("Scan is not supported across multiple nodes within a cluster");
 	}
 
+	/**
+	 * Use a {@link Cursor} to iterate over keys stored at the given {@link RedisClusterNode}.
+	 *
+	 * @param node must not be {@literal null}.
+	 * @param options must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.1
+	 */
 	Cursor<byte[]> scan(RedisClusterNode node, ScanOptions options) {
 
 		Assert.notNull(node, "RedisClusterNode must not be null!");
-		Assert.notNull(options, "Pattern must not be null!");
+		Assert.notNull(options, "Options must not be null!");
 
 		return connection.getClusterCommandExecutor()
 				.executeCommandOnSingleNode((JedisClusterCommandCallback<Cursor<byte[]>>) client -> {

src/main/java/org/springframework/data/redis/connection/lettuce/LettuceClusterKeyCommands.java

@@ -183,10 +183,18 @@ class LettuceClusterKeyCommands extends LettuceKeyCommands {
 				.getValue());
 	}
 
+	/**
+	 * Use a {@link Cursor} to iterate over keys stored at the given {@link RedisClusterNode}.
+	 *
+	 * @param node must not be {@literal null}.
+	 * @param options must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.1
+	 */
 	Cursor<byte[]> scan(RedisClusterNode node, ScanOptions options) {
 
 		Assert.notNull(node, "RedisClusterNode must not be null!");
-		Assert.notNull(options, "Pattern must not be null!");
+		Assert.notNull(options, "Options must not be null!");
 
 		return connection.getClusterCommandExecutor()
 				.executeCommandOnSingleNode((LettuceClusterCommandCallback<ScanCursor<byte[]>>) client -> {
@@ -195,12 +203,11 @@ class LettuceClusterKeyCommands extends LettuceKeyCommands {
 
 						@Override
 						protected LettuceScanIteration<byte[]> doScan(io.lettuce.core.ScanCursor cursor, ScanOptions options) {
+
 							ScanArgs scanArgs = connection.getScanArgs(options);
 
 							KeyScanCursor<byte[]> keyScanCursor = client.scan(cursor, scanArgs);
-							List<byte[]> keys = keyScanCursor.getKeys();
-
-							return new LettuceScanIteration<>(keyScanCursor, keys);
+							return new LettuceScanIteration<>(keyScanCursor, keyScanCursor.getKeys());
 						}
 
 					}.open();

src/main/java/org/springframework/data/redis/connection/lettuce/LettuceScanCursor.java

@@ -27,14 +27,14 @@ import org.springframework.lang.Nullable;
  * across a Redis Cluster.
  * <p/>
  * The cursor state uses Lettuce's stateful {@link io.lettuce.core.ScanCursor} to keep track of scanning progress.
- * Lettuce's cursor stores scanning progress inside its cursor so using a primitive {@code long} is not sufficient.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 2.1
  */
 abstract class LettuceScanCursor<T> extends ScanCursor<T> {
 
-	@Nullable private io.lettuce.core.ScanCursor state;
+	private @Nullable io.lettuce.core.ScanCursor state;
 
 	/**
 	 * Creates a new {@link LettuceScanCursor} given {@link ScanOptions}.
@@ -93,19 +93,22 @@ abstract class LettuceScanCursor<T> extends ScanCursor<T> {
 	 *
 	 * @param cursor must not be {@literal null}.
 	 * @param options must not be {@literal null}.
-	 * @return
+	 * @return never {@literal null}
 	 */
 	protected abstract LettuceScanIteration<T> doScan(io.lettuce.core.ScanCursor cursor, ScanOptions options);
 
 	/**
 	 * Lettuce-specific extension to {@link ScanIteration} keeping track of the original
 	 * {@link io.lettuce.core.ScanCursor} object.
+	 *
+	 * @author Mark Paluch
 	 */
 	static class LettuceScanIteration<T> extends ScanIteration<T> {
 
 		private final io.lettuce.core.ScanCursor cursor;
 
 		LettuceScanIteration(io.lettuce.core.ScanCursor cursor, Collection<T> items) {
+
 			super(Long.parseLong(cursor.getCursor()), items);
 			this.cursor = cursor;
 		}