Add lengthOfValue (HSTRLEN) to ReactiveHashOperations

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

@@ -51,6 +51,7 @@
  * @author Mark Paluch
  * @author Christoph Strobl
  * @author John Blum
+ * @author Jewoo Shin
  * @since 2.0
  */
 class DefaultReactiveHashOperations<H, HK, HV> implements ReactiveHashOperations<H, HK, HV> {
@@ -215,6 +216,15 @@ public Flux<HK> keys(H key) {
 				.map(this::readRequiredHashKey));
 	}
 
+	@Override
+	public Mono<Long> lengthOfValue(H key, HK hashKey) {
+
+		Assert.notNull(key, "Key must not be null");
+		Assert.notNull(hashKey, "Hash key must not be null");
+
+		return createMono(hashCommands -> hashCommands.hStrLen(rawKey(key), rawHashKey(hashKey)));
+	}
+
 	@Override
 	public Mono<Long> size(H key) {
 

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

@@ -45,6 +45,7 @@
  * @author Mark Paluch
  * @author Christoph Strobl
  * @author Viktoriya Kutsarova
+ * @author Jewoo Shin
  * @since 2.0
  */
 public interface ReactiveHashOperations<H, HK, HV> {
@@ -200,6 +201,18 @@ Mono<Boolean> putAndExpire(H key, Map<? extends HK, ? extends HV> map,
 	 */
 	Flux<HK> keys(H key);
 
+	/**
+	 * Returns the length of the value associated with {@code hashKey}. If either the {@code key} or the {@code hashKey}
+	 * do not exist, {@code 0} is emitted.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param hashKey must not be {@literal null}.
+	 * @return {@link Mono} emitting the length of the value associated with {@code hashKey}.
+	 * @since 4.2
+	 * @see <a href="https://redis.io/commands/hstrlen">Redis Documentation: HSTRLEN</a>
+	 */
+	Mono<Long> lengthOfValue(H key, HK hashKey);
+
 	/**
 	 * Get size of hash at {@code key}.
 	 *

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

@@ -58,6 +58,7 @@
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Jewoo Shin
  */
 @ParameterizedClass
 @MethodSource("testParams")
@@ -364,6 +365,26 @@ void keys() {
 				.verifyComplete();
 	}
 
+	@Test // GH-3376
+	void lengthOfValue() {
+
+		assumeThat(hashValueFactory instanceof StringObjectFactory).isTrue();
+
+		K key = keyFactory.instance();
+		HK hashkey1 = hashKeyFactory.instance();
+		HV hashvalue1 = hashValueFactory.instance();
+
+		HK hashkey2 = hashKeyFactory.instance();
+		HV hashvalue2 = hashValueFactory.instance();
+
+		putAll(key, hashkey1, hashvalue1, hashkey2, hashvalue2);
+
+		hashOperations.lengthOfValue(key, hashkey1) //
+				.as(StepVerifier::create) //
+				.expectNext((long) hashvalue1.toString().length()) //
+				.verifyComplete();
+	}
+
 	@Test // DATAREDIS-602
 	void size() {