Support scan in RedisTemplate.

Closes #2260
Original pull request: #2263.

Author: lc77254

src/main/java/org/springframework/data/redis/core/RedisOperations.java

@@ -45,6 +45,7 @@
  * @author Mark Paluch
  * @author ihaohong
  * @author Todd Merrill
+ * @author Chen Li
  */
 public interface RedisOperations<K, V> {
 
@@ -259,6 +260,16 @@ <T> T execute(RedisScript<T> script, RedisSerializer<?> argsSerializer, RedisSer
 	@Nullable
 	Set<K> keys(K pattern);
 
+	/**
+	 * Use a {@link Cursor} to iterate over keys. <br />
+	 * <strong>Important:</strong> Call {@link Cursor#close()} when done to avoid resource leak.
+	 *
+	 * @param options must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @see <a href="https://redis.io/commands/scan">Redis Documentation: SCAN</a>
+	 */
+	Cursor<K> scan(ScanOptions options);
+
 	/**
 	 * Return a random key from the keyspace.
 	 *

src/main/java/org/springframework/data/redis/core/RedisTemplate.java

@@ -83,6 +83,7 @@
  * @author Mark Paluch
  * @author Denis Zavedeev
  * @author ihaohong
+ * @author Chen Li
  * @param <K> the Redis key type against which the template works (usually a String)
  * @param <V> the Redis value type against which the template works
  * @see StringRedisTemplate
@@ -897,6 +898,19 @@ public Set<K> keys(K pattern) {
 		return keySerializer != null ? SerializationUtils.deserialize(rawKeys, keySerializer) : (Set<K>) rawKeys;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.redis.core.RedisOperations#scan(java.lang.Object)
+	 */
+	@Override
+	public Cursor<K> scan(ScanOptions options) {
+		Assert.notNull(options, "ScanOptions must not be null!");
+
+		return executeWithStickyConnection(
+				(RedisCallback<Cursor<K>>) connection -> new ConvertingCursor<>(connection.scan(options),
+						this::deserializeKey));
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.redis.core.RedisOperations#persist(java.lang.Object)

src/test/java/org/springframework/data/redis/core/RedisTemplateIntegrationTests.java

@@ -62,6 +62,7 @@
  * @author Mark Paluch
  * @author ihaohong
  * @author Hendrik Duerkop
+ * @author Chen Li
  */
 @MethodSource("testParams")
 public class RedisTemplateIntegrationTests<K, V> {
@@ -126,6 +127,22 @@ void testKeys() throws Exception {
 		assertThat(redisTemplate.keys(keyPattern)).isNotNull();
 	}
 
+	@ParameterizedRedisTest // GH-2260
+	void testScan() {
+		K key1 = keyFactory.instance();
+		V value1 = valueFactory.instance();
+		assumeThat(key1 instanceof String || key1 instanceof byte[]).isTrue();
+		redisTemplate.opsForValue().set(key1, value1);
+		Cursor<K> cursor = redisTemplate.scan(ScanOptions.scanOptions().count(1).build());
+		long count = 0;
+		while (cursor.hasNext()) {
+			assertThat(cursor.next()).isEqualTo(key1);
+			count++;
+		}
+		cursor.close();
+		assertThat(count).isEqualTo(1);
+	}
+
 	@SuppressWarnings("rawtypes")
 	@ParameterizedRedisTest
 	void testTemplateNotInitialized() throws Exception {