Add multiple reactive keys exist checker

Author: AnneMayor

src/main/java/org/springframework/data/redis/connection/ReactiveKeyCommands.java

@@ -175,6 +175,20 @@ default Mono<Boolean> exists(ByteBuffer key) {
 
 		return exists(Mono.just(new KeyCommand(key))).next().map(BooleanResponse::getOutput);
 	}
+	/**
+	 * Determine if given all {@literal keys} exist.
+	 *
+	 * @param keys must not be {@literal null} or {@literal empty}.
+	 * @return {@link Mono} emitting {@literal true} if all keys exist.
+	 * @see <a href="https://redis.io/commands/exists">Redis Documentation: EXISTS</a>
+	 */
+	default Mono<Boolean> exists(List<ByteBuffer> keys) {
+
+		Assert.notNull(keys, "Keys must not be null");
+		Assert.notEmpty(keys, "Keys must not be empty");
+
+		return exists(Flux.fromIterable(keys).map(KeyCommand::new)).all(BooleanResponse::getOutput);
+	}
 
 	/**
 	 * Determine if given {@literal key} exists.

src/test/java/org/springframework/data/redis/connection/lettuce/LettuceReactiveKeyCommandsIntegrationTests.java

@@ -66,6 +66,26 @@ void existsShouldReturnFalseForNonExistingKeys() {
 		connection.keyCommands().exists(KEY_1_BBUFFER).as(StepVerifier::create).expectNext(false).verifyComplete();
 	}
 
+	@ParameterizedRedisTest
+	void existsShouldReturnTrueWhenKeysExist() {
+
+		nativeCommands.set(KEY_1, VALUE_1);
+		nativeCommands.set(KEY_2, VALUE_2);
+
+		connection.keyCommands().exists(Arrays.asList(KEY_1_BBUFFER, KEY_2_BBUFFER)).as(StepVerifier::create)
+				.expectNext(true)
+				.verifyComplete();
+	}
+
+	@ParameterizedRedisTest
+	void existsShouldReturnFalseWhenKeysDoNotExist() {
+
+		connection.keyCommands().exists(Arrays.asList(KEY_1_BBUFFER, KEY_2_BBUFFER)).as(StepVerifier::create)
+				.expectNext(false) //
+				.verifyComplete();
+	}
+
+
 	@ParameterizedRedisTest // DATAREDIS-525
 	void typeShouldReturnTypeCorrectly() {
 
@@ -164,7 +184,7 @@ void renameShouldAlterKeyNameCorrectly() {
 		connection.keyCommands().rename(KEY_1_BBUFFER, KEY_2_BBUFFER).as(StepVerifier::create).expectNext(true)
 				.verifyComplete();
 		assertThat(nativeCommands.exists(KEY_2)).isEqualTo(1L);
-		assertThat(nativeCommands.exists(KEY_1)).isEqualTo(0L);
+		assertThat(nativeCommands.exists(KEY_1)).isZero();
 	}
 
 	@ParameterizedRedisTest // DATAREDIS-525
@@ -183,7 +203,7 @@ void renameNXShouldAlterKeyNameCorrectly() {
 				.verifyComplete();
 
 		assertThat(nativeCommands.exists(KEY_2)).isEqualTo(1L);
-		assertThat(nativeCommands.exists(KEY_1)).isEqualTo(0L);
+		assertThat(nativeCommands.exists(KEY_1)).isZero();
 	}
 
 	@ParameterizedRedisTest // DATAREDIS-525
@@ -395,7 +415,7 @@ void shouldMoveToDatabase() {
 				.expectNext(true) //
 				.expectComplete() //
 				.verify();
-		assertThat(nativeCommands.exists(KEY_1)).isEqualTo(0L);
+		assertThat(nativeCommands.exists(KEY_1)).isZero();
 	}
 
 	@ParameterizedRedisTest // DATAREDIS-694