修复reactive redis timeout可能导致NPE问题

jetlinks-standalone/src/main/java/org/springframework/data/redis/connection/ReactiveHashCommands.java

@@ -0,0 +1,704 @@
+/*
+ * Copyright 2016-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.redis.connection;
+
+import org.reactivestreams.Publisher;
+import org.springframework.dao.InvalidDataAccessApiUsageException;
+import org.springframework.data.redis.connection.ReactiveRedisConnection.*;
+import org.springframework.data.redis.core.ScanOptions;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.nio.ByteBuffer;
+import java.util.*;
+import java.util.function.Function;
+
+/**
+ * Redis Hash commands executed using reactive infrastructure.
+ *
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @since 2.0
+ */
+public interface ReactiveHashCommands {
+
+	/**
+	 * {@literal HSET} {@link Command}.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href="https://redis.io/commands/hset">Redis Documentation: HSET</a>
+	 */
+	class HSetCommand extends KeyCommand {
+
+		private static final ByteBuffer SINGLE_VALUE_KEY = ByteBuffer.allocate(0);
+		private final Map<ByteBuffer, ByteBuffer> fieldValueMap;
+		private final boolean upsert;
+
+		private HSetCommand(@Nullable ByteBuffer key, Map<ByteBuffer, ByteBuffer> keyValueMap, boolean upsert) {
+
+			super(key);
+
+			this.fieldValueMap = keyValueMap;
+			this.upsert = upsert;
+		}
+
+		/**
+		 * Creates a new {@link HSetCommand} given a {@link ByteBuffer key}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return a new {@link HSetCommand} for {@link ByteBuffer key}.
+		 */
+		public static HSetCommand value(ByteBuffer value) {
+
+			Assert.notNull(value, "Value must not be null!");
+
+			return new HSetCommand(null, Collections.singletonMap(SINGLE_VALUE_KEY, value), Boolean.TRUE);
+		}
+
+		/**
+		 * Creates a new {@link HSetCommand} given a {@link Map} of field values.
+		 *
+		 * @param fieldValueMap must not be {@literal null}.
+		 * @return a new {@link HSetCommand} for a {@link Map} of field values.
+		 */
+		public static HSetCommand fieldValues(Map<ByteBuffer, ByteBuffer> fieldValueMap) {
+
+			Assert.notNull(fieldValueMap, "Field values map must not be null!");
+
+			return new HSetCommand(null, fieldValueMap, Boolean.TRUE);
+		}
+
+		/**
+		 * Applies a field. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return a new {@link HSetCommand} with {@literal field} applied.
+		 */
+		public HSetCommand ofField(ByteBuffer field) {
+
+			if (!fieldValueMap.containsKey(SINGLE_VALUE_KEY)) {
+				throw new InvalidDataAccessApiUsageException("Value has not been set.");
+			}
+
+			Assert.notNull(field, "Field not be null!");
+
+			return new HSetCommand(getKey(), Collections.singletonMap(field, fieldValueMap.get(SINGLE_VALUE_KEY)), upsert);
+		}
+
+		/**
+		 * Applies the {@literal key}. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @param key must not be {@literal null}.
+		 * @return a new {@link HSetCommand} with {@literal key} applied.
+		 */
+		public HSetCommand forKey(ByteBuffer key) {
+
+			Assert.notNull(key, "Key not be null!");
+
+			return new HSetCommand(key, fieldValueMap, upsert);
+		}
+
+		/**
+		 * Disable upsert. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @return a new {@link HSetCommand} with upsert disabled.
+		 */
+		public HSetCommand ifValueNotExists() {
+			return new HSetCommand(getKey(), fieldValueMap, Boolean.FALSE);
+		}
+
+		/**
+		 * @return
+		 */
+		public boolean isUpsert() {
+			return upsert;
+		}
+
+		/**
+		 * @return never {@literal null}.
+		 */
+		public Map<ByteBuffer, ByteBuffer> getFieldValueMap() {
+			return fieldValueMap;
+		}
+	}
+
+	/**
+	 * Set the {@literal value} of a hash {@literal field}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @param value must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hset">Redis Documentation: HSET</a>
+	 */
+	default Mono<Boolean> hSet(ByteBuffer key, ByteBuffer field, ByteBuffer value) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(field, "Field must not be null!");
+		Assert.notNull(value, "Value must not be null!");
+
+		return hSet(Mono.just(HSetCommand.value(value).ofField(field).forKey(key)))
+				.next()
+				.flatMap(response->Mono.justOrEmpty(response.getOutput()));
+	}
+
+	/**
+	 * Set the {@literal value} of a hash {@literal field}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @param value must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hsetnx">Redis Documentation: HSETNX</a>
+	 */
+	default Mono<Boolean> hSetNX(ByteBuffer key, ByteBuffer field, ByteBuffer value) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(field, "Field must not be null!");
+		Assert.notNull(value, "Value must not be null!");
+
+		return hSet(Mono.just(HSetCommand.value(value).ofField(field).forKey(key).ifValueNotExists()))
+				.next()
+				.flatMap(response->Mono.justOrEmpty(response.getOutput()));
+	}
+
+	/**
+	 * Set multiple hash fields to multiple values using data provided in {@literal fieldValueMap}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param fieldValueMap must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hmset">Redis Documentation: HMSET</a>
+	 */
+	default Mono<Boolean> hMSet(ByteBuffer key, Map<ByteBuffer, ByteBuffer> fieldValueMap) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(fieldValueMap, "Field must not be null!");
+
+		return hSet(Mono.just(HSetCommand.fieldValues(fieldValueMap).forKey(key))).next().map(it -> true);
+	}
+
+	/**
+	 * Set the {@literal value} of a hash {@literal field}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hset">Redis Documentation: HSET</a>
+	 */
+	Flux<BooleanResponse<HSetCommand>> hSet(Publisher<HSetCommand> commands);
+
+	/**
+	 * {@literal HGET} {@link Command}.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href="https://redis.io/commands/hget">Redis Documentation: HGET</a>
+	 */
+	class HGetCommand extends KeyCommand {
+
+		private List<ByteBuffer> fields;
+
+		private HGetCommand(@Nullable ByteBuffer key, List<ByteBuffer> fields) {
+
+			super(key);
+
+			this.fields = fields;
+		}
+
+		/**
+		 * Creates a new {@link HGetCommand} given a {@link ByteBuffer field name}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return a new {@link HGetCommand} for a {@link ByteBuffer field name}.
+		 */
+		public static HGetCommand field(ByteBuffer field) {
+
+			Assert.notNull(field, "Field must not be null!");
+
+			return new HGetCommand(null, Collections.singletonList(field));
+		}
+
+		/**
+		 * Creates a new {@link HGetCommand} given a {@link Collection} of field names.
+		 *
+		 * @param fields must not be {@literal null}.
+		 * @return a new {@link HGetCommand} for a {@link Collection} of field names.
+		 */
+		public static HGetCommand fields(Collection<ByteBuffer> fields) {
+
+			Assert.notNull(fields, "Fields must not be null!");
+
+			return new HGetCommand(null, new ArrayList<>(fields));
+		}
+
+		/**
+		 * Applies the hash {@literal key}. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @param key must not be {@literal null}.
+		 * @return a new {@link HGetCommand} with {@literal key} applied.
+		 */
+		public HGetCommand from(ByteBuffer key) {
+
+			Assert.notNull(key, "Key must not be null!");
+
+			return new HGetCommand(key, fields);
+		}
+
+		/**
+		 * @return never {@literal null}.
+		 */
+		public List<ByteBuffer> getFields() {
+			return fields;
+		}
+	}
+
+	/**
+	 * Get value for given {@literal field} from hash at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hget">Redis Documentation: HGET</a>
+	 */
+	default Mono<ByteBuffer> hGet(ByteBuffer key, ByteBuffer field) {
+		return hMGet(key, Collections.singletonList(field)).flatMapIterable(Function.identity()).next();
+	}
+
+	/**
+	 * Get values for given {@literal fields} from hash at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param fields must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hmget">Redis Documentation: HMGET</a>
+	 */
+	default Mono<List<ByteBuffer>> hMGet(ByteBuffer key, Collection<ByteBuffer> fields) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(fields, "Fields must not be null!");
+
+		return hMGet(Mono.just(HGetCommand.fields(fields).from(key)))
+				.next()
+				.flatMap(res->Mono.justOrEmpty(res.getOutput()));
+	}
+
+	/**
+	 * Get values for given {@literal fields} from hash at {@literal key}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hmget">Redis Documentation: HMGET</a>
+	 */
+	Flux<MultiValueResponse<HGetCommand, ByteBuffer>> hMGet(Publisher<HGetCommand> commands);
+
+	/**
+	 * {@literal HEXISTS} {@link Command}.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href="https://redis.io/commands/hexists">Redis Documentation: HEXISTS</a>
+	 */
+	class HExistsCommand extends KeyCommand {
+
+		private final ByteBuffer field;
+
+		private HExistsCommand(@Nullable ByteBuffer key, ByteBuffer field) {
+
+			super(key);
+
+			this.field = field;
+		}
+
+		/**
+		 * Creates a new {@link HExistsCommand} given a {@link ByteBuffer field name}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return a new {@link HExistsCommand} for a {@link ByteBuffer field name}.
+		 */
+		public static HExistsCommand field(ByteBuffer field) {
+
+			Assert.notNull(field, "Field must not be null!");
+
+			return new HExistsCommand(null, field);
+		}
+
+		/**
+		 * Applies the hash {@literal key}. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @param key must not be {@literal null}.
+		 * @return a new {@link HExistsCommand} with {@literal key} applied.
+		 */
+		public HExistsCommand in(ByteBuffer key) {
+
+			Assert.notNull(key, "Key must not be null!");
+
+			return new HExistsCommand(key, field);
+		}
+
+		/**
+		 * @return never {@literal null}.
+		 */
+		public ByteBuffer getField() {
+			return field;
+		}
+	}
+
+	/**
+	 * Determine if given hash {@literal field} exists.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hexists">Redis Documentation: HEXISTS</a>
+	 */
+	default Mono<Boolean> hExists(ByteBuffer key, ByteBuffer field) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(field, "Field must not be null!");
+
+		return hExists(Mono.just(HExistsCommand.field(field).in(key)))
+				.next()
+				.flatMap(response->Mono.justOrEmpty(response.getOutput()));
+	}
+
+	/**
+	 * Determine if given hash {@literal field} exists.
+	 *
+	 * @param commands
+	 * @return
+	 * @see <a href="https://redis.io/commands/hexists">Redis Documentation: HEXISTS</a>
+	 */
+	Flux<BooleanResponse<HExistsCommand>> hExists(Publisher<HExistsCommand> commands);
+
+	/**
+	 * @author Christoph Strobl
+	 * @see <a href="https://redis.io/commands/hdel">Redis Documentation: HDEL</a>
+	 */
+	class HDelCommand extends KeyCommand {
+
+		private final List<ByteBuffer> fields;
+
+		private HDelCommand(@Nullable ByteBuffer key, List<ByteBuffer> fields) {
+
+			super(key);
+
+			this.fields = fields;
+		}
+
+		/**
+		 * Creates a new {@link HDelCommand} given a {@link ByteBuffer field name}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return a new {@link HDelCommand} for a {@link ByteBuffer field name}.
+		 */
+		public static HDelCommand field(ByteBuffer field) {
+
+			Assert.notNull(field, "Field must not be null!");
+
+			return new HDelCommand(null, Collections.singletonList(field));
+		}
+
+		/**
+		 * Creates a new {@link HDelCommand} given a {@link Collection} of field names.
+		 *
+		 * @param fields must not be {@literal null}.
+		 * @return a new {@link HDelCommand} for a {@link Collection} of field names.
+		 */
+		public static HDelCommand fields(Collection<ByteBuffer> fields) {
+
+			Assert.notNull(fields, "Fields must not be null!");
+
+			return new HDelCommand(null, new ArrayList<>(fields));
+		}
+
+		/**
+		 * Applies the hash {@literal key}. Constructs a new command instance with all previously configured properties.
+		 *
+		 * @param key must not be {@literal null}.
+		 * @return a new {@link HDelCommand} with {@literal key} applied.
+		 */
+		public HDelCommand from(ByteBuffer key) {
+
+			Assert.notNull(key, "Key must not be null!");
+
+			return new HDelCommand(key, fields);
+		}
+
+		/**
+		 * @return never {@literal null}.
+		 */
+		public List<ByteBuffer> getFields() {
+			return fields;
+		}
+	}
+
+	/**
+	 * Delete given hash {@literal field}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hdel">Redis Documentation: HDEL</a>
+	 */
+	default Mono<Boolean> hDel(ByteBuffer key, ByteBuffer field) {
+
+		Assert.notNull(field, "Field must not be null!");
+
+		return hDel(key, Collections.singletonList(field)).map(val -> val > 0 ? Boolean.TRUE : Boolean.FALSE);
+	}
+
+	/**
+	 * Delete given hash {@literal fields}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param fields must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hdel">Redis Documentation: HDEL</a>
+	 */
+	default Mono<Long> hDel(ByteBuffer key, Collection<ByteBuffer> fields) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(fields, "Fields must not be null!");
+
+		return hDel(Mono.just(HDelCommand.fields(fields).from(key)))
+				.next()
+				.flatMap(response->Mono.justOrEmpty(response.getOutput()));
+	}
+
+	/**
+	 * Delete given hash {@literal fields}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hdel">Redis Documentation: HDEL</a>
+	 */
+	Flux<NumericResponse<HDelCommand, Long>> hDel(Publisher<HDelCommand> commands);
+
+	/**
+	 * Get size of hash at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hlen">Redis Documentation: HLEN</a>
+	 */
+	default Mono<Long> hLen(ByteBuffer key) {
+
+		Assert.notNull(key, "Key must not be null!");
+
+		return hLen(Mono.just(new KeyCommand(key)))
+				.next()
+				.flatMap(response->Mono.justOrEmpty(response.getOutput()));
+	}
+
+	/**
+	 * Get size of hash at {@literal key}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hlen">Redis Documentation: HLEN</a>
+	 */
+	Flux<NumericResponse<KeyCommand, Long>> hLen(Publisher<KeyCommand> commands);
+
+	/**
+	 * Get key set (fields) of hash at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hkeys">Redis Documentation: HKEYS</a>
+	 */
+	default Flux<ByteBuffer> hKeys(ByteBuffer key) {
+
+		Assert.notNull(key, "Key must not be null!");
+
+		return hKeys(Mono.just(new KeyCommand(key)))
+				.flatMap(CommandResponse::getOutput);
+	}
+
+	/**
+	 * Get key set (fields) of hash at {@literal key}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hkeys">Redis Documentation: HKEYS</a>
+	 */
+	Flux<CommandResponse<KeyCommand, Flux<ByteBuffer>>> hKeys(Publisher<KeyCommand> commands);
+
+	/**
+	 * Get entry set (values) of hash at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hvals">Redis Documentation: HVALS</a>
+	 */
+	default Flux<ByteBuffer> hVals(ByteBuffer key) {
+
+		Assert.notNull(key, "Key must not be null!");
+
+		return hVals(Mono.just(new KeyCommand(key))).flatMap(CommandResponse::getOutput);
+	}
+
+	/**
+	 * Get entry set (values) of hash at {@literal key}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hvals">Redis Documentation: HVALS</a>
+	 */
+	Flux<CommandResponse<KeyCommand, Flux<ByteBuffer>>> hVals(Publisher<KeyCommand> commands);
+
+	/**
+	 * Get entire hash stored at {@literal key}.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hgetall">Redis Documentation: HGETALL</a>
+	 */
+	default Flux<Map.Entry<ByteBuffer, ByteBuffer>> hGetAll(ByteBuffer key) {
+
+		Assert.notNull(key, "Key must not be null!");
+
+		return hGetAll(Mono.just(new KeyCommand(key))).flatMap(CommandResponse::getOutput);
+	}
+
+	/**
+	 * Get entire hash stored at {@literal key}.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return
+	 * @see <a href="https://redis.io/commands/hgetall">Redis Documentation: HGETALL</a>
+	 */
+	Flux<CommandResponse<KeyCommand, Flux<Map.Entry<ByteBuffer, ByteBuffer>>>> hGetAll(Publisher<KeyCommand> commands);
+
+	/**
+	 * Use a {@link Flux} to iterate over entries in the hash at {@code key}. The resulting {@link Flux} acts as a cursor
+	 * and issues {@code HSCAN} commands itself as long as the subscriber signals demand.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @return the {@link Flux} emitting {@link Map.Entry entries} one by one.
+	 * @throws IllegalArgumentException in case the given key is {@literal null}.
+	 * @see <a href="https://redis.io/commands/hscan">Redis Documentation: HSCAN</a>
+	 * @since 2.1
+	 */
+	default Flux<Map.Entry<ByteBuffer, ByteBuffer>> hScan(ByteBuffer key) {
+		return hScan(key, ScanOptions.NONE);
+	}
+
+	/**
+	 * Use a {@link Flux} to iterate over entries in the hash at {@code key} given {@link ScanOptions}. The resulting
+	 * {@link Flux} acts as a cursor and issues {@code HSCAN} commands itself as long as the subscriber signals demand.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param options must not be {@literal null}. Use {@link ScanOptions#NONE} instead.
+	 * @return the {@link Flux} emitting the raw {@link Map.Entry entries} one by one.
+	 * @throws IllegalArgumentException in case one of the required arguments is {@literal null}.
+	 * @see <a href="https://redis.io/commands/hscan">Redis Documentation: HSCAN</a>
+	 * @since 2.1
+	 */
+	default Flux<Map.Entry<ByteBuffer, ByteBuffer>> hScan(ByteBuffer key, ScanOptions options) {
+
+		return hScan(Mono.just(KeyScanCommand.key(key).withOptions(options))).map(CommandResponse::getOutput)
+				.flatMap(it -> it);
+	}
+
+	/**
+	 * Use a {@link Flux} to iterate over entries in the hash at {@code key}. The resulting {@link Flux} acts as a cursor
+	 * and issues {@code HSCAN} commands itself as long as the subscriber signals demand.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return the {@link Flux} emitting {@link CommandResponse} one by one.
+	 * @see <a href="https://redis.io/commands/hscan">Redis Documentation: HSCAN</a>
+	 * @since 2.1
+	 */
+	Flux<CommandResponse<KeyCommand, Flux<Map.Entry<ByteBuffer, ByteBuffer>>>> hScan(Publisher<KeyScanCommand> commands);
+
+	/**
+	 * @author Christoph Strobl
+	 * @see <a href="https://redis.io/commands/hstrlen">Redis Documentation: HSTRLEN</a>
+	 * @since 2.1
+	 */
+	class HStrLenCommand extends KeyCommand {
+
+		private ByteBuffer field;
+
+		/**
+		 * Creates a new {@link HStrLenCommand} given a {@code key}.
+		 *
+		 * @param key can be {@literal null}.
+		 * @param field must not be {@literal null}.
+		 */
+		private HStrLenCommand(@Nullable ByteBuffer key, ByteBuffer field) {
+
+			super(key);
+			this.field = field;
+		}
+
+		/**
+		 * Specify the {@code field} within the hash to get the length of the {@code value} of.ø
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return new instance of {@link HStrLenCommand}.
+		 */
+		public static HStrLenCommand lengthOf(ByteBuffer field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			return new HStrLenCommand(null, field);
+		}
+
+		/**
+		 * Define the {@code key} the hash is stored at.
+		 *
+		 * @param key must not be {@literal null}.
+		 * @return new instance of {@link HStrLenCommand}.
+		 */
+		public HStrLenCommand from(ByteBuffer key) {
+			return new HStrLenCommand(key, field);
+		}
+
+		/**
+		 * @return the field.
+		 */
+		public ByteBuffer getField() {
+			return field;
+		}
+	}
+
+	/**
+	 * Get the length of the value associated with {@code field}. If either the {@code key} or the {@code field} do not
+	 * exist, {@code 0} is emitted.
+	 *
+	 * @param key must not be {@literal null}.
+	 * @param field must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.1
+	 */
+	default Mono<Long> hStrLen(ByteBuffer key, ByteBuffer field) {
+
+		Assert.notNull(key, "Key must not be null!");
+		Assert.notNull(field, "Field must not be null!");
+
+		return hStrLen(Mono.just(HStrLenCommand.lengthOf(field).from(key))).next().map(NumericResponse::getOutput);
+	}
+
+	/**
+	 * Get the length of the value associated with {@code field}. If either the {@code key} or the {@code field} do not
+	 * exist, {@code 0} is emitted.
+	 *
+	 * @param commands must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.1
+	 */
+	Flux<NumericResponse<HStrLenCommand, Long>> hStrLen(Publisher<HStrLenCommand> commands);
+}