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摘要

    是 Redis 的一款高级 Java 客户端，已成为 SpringBoot 2.0 版本默认的 redis 客户端。Lettuce 后起之秀，不仅功能丰富，提供了很多新的功能特性，比如异步操作、响应式编程等，还解决了 Jedis 中线程不安全的问题。

Lettuce

    <dependency><groupId>io.lettuce</groupId><artifactId>lettuce-core</artifactId><version>6.2.5.RELEASE</version></dependency>

同步操作

基本上 Jedis 支持的同步命令操作，Lettuce 都支持。

Lettuce 的 api 操作如下！

public class LettuceUtil {public static void main(String[] args) {RedisURI redisUri = RedisURI.builder().withHost("127.0.0.1").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();RedisClient redisClient = RedisClient.create(redisUri);StatefulRedisConnection<String, String> connection = redisClient.connect();//获取同步操作命令工具RedisCommands<String, String> commands = connection.sync();System.out.println("清空数据："+commands.flushdb());System.out.println("判断某个键是否存在："+commands.exists("username"));System.out.println("新增<'username','xmr'>的键值对："+commands.set("username", "xmr"));System.out.println("新增<'password','password'>的键值对："+commands.set("password", "123"));System.out.println("获取<'password'>键的值："+commands.get("password"));System.out.println("系统中所有的键如下：" + commands.keys("*"));System.out.println("删除键password:"+commands.del("password"));System.out.println("判断键password是否存在："+commands.exists("password"));System.out.println("设置键username的过期时间为5s:"+commands.expire("username", 5L));System.out.println("查看键username的剩余生存时间："+commands.ttl("username"));System.out.println("移除键username的生存时间："+commands.persist("username"));System.out.println("查看键username的剩余生存时间："+commands.ttl("username"));System.out.println("查看键username所存储的值的类型："+commands.type("username"));connection.close();redisClient.shutdown();}
}

异步操作

Lettuce 还支持异步操作，将上面的操作改成异步处理，结果如下！

public class LettuceUtil {public static void main(String[] args) throws Exception {RedisURI redisUri = RedisURI.builder().withHost("127.0.0.1").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();RedisClient redisClient = RedisClient.create(redisUri);StatefulRedisConnection<String, String> connection = redisClient.connect();//获取异步操作命令工具RedisAsyncCommands<String, String> commands = connection.async();System.out.println("清空数据："+commands.flushdb().get());System.out.println("判断某个键是否存在："+commands.exists("username").get());System.out.println("新增<'username','xmr'>的键值对："+commands.set("username", "xmr").get());System.out.println("新增<'password','password'>的键值对："+commands.set("password", "123").get());System.out.println("获取<'password'>键的值："+commands.get("password").get());System.out.println("系统中所有的键如下：" + commands.keys("*").get());System.out.println("删除键password:"+commands.del("password").get());System.out.println("判断键password是否存在："+commands.exists("password").get());System.out.println("设置键username的过期时间为5s:"+commands.expire("username", 5L).get());System.out.println("查看键username的剩余生存时间："+commands.ttl("username").get());System.out.println("移除键username的生存时间："+commands.persist("username").get());System.out.println("查看键username的剩余生存时间："+commands.ttl("username").get());System.out.println("查看键username所存储的值的类型："+commands.type("username").get());connection.close();redisClient.shutdown();}
}

响应式编程

        Lettuce 除了支持异步编程以外，还支持响应式编程，Lettuce 引入的响应式编程框架是Project Reactor，如果没有响应式编程经验可以先自行了解一下，访问地址https://projectreactor.io/。

响应式编程使用案例如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {RedisURI redisUri = RedisURI.builder().withHost("127.0.0.1").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();RedisClient redisClient = RedisClient.create(redisUri);StatefulRedisConnection<String, String> connection = redisClient.connect();//获取响应式API操作命令工具RedisReactiveCommands<String, String> commands = connection.reactive();Mono<String> setc = commands.set("name", "mayun");System.out.println(setc.block());Mono<String> getc = commands.get("name");getc.subscribe(System.out::println);Flux<String> keys = commands.keys("*");keys.subscribe(System.out::println);//开启一个事务，先把count设置为1，再将count自增1commands.multi().doOnSuccess(r -> {commands.set("count", "1").doOnNext(value -> System.out.println("count1：" +  value)).subscribe();commands.incr("count").doOnNext(value -> System.out.println("count2：" +  value)).subscribe();}).flatMap(s -> commands.exec()).doOnNext(transactionResult -> System.out.println("transactionResult：" + transactionResult.wasDiscarded())).subscribe();Thread.sleep(1000 * 5);connection.close();redisClient.shutdown();}
}

发布和订阅

        Lettuce 还支持 redis 的消息发布和订阅，具体实现案例如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {RedisURI redisUri = RedisURI.builder().withHost("127.0.0.1").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();RedisClient redisClient = RedisClient.create(redisUri);//获取发布订阅操作命令工具StatefulRedisPubSubConnection<String, String> pubsubConn = redisClient.connectPubSub();pubsubConn.addListener(new RedisPubSubListener<String, String>() {@Overridepublic void unsubscribed(String channel, long count) {System.out.println("[unsubscribed]" + channel);}@Overridepublic void subscribed(String channel, long count) {System.out.println("[subscribed]" + channel);}@Overridepublic void punsubscribed(String pattern, long count) {System.out.println("[punsubscribed]" + pattern);}@Overridepublic void psubscribed(String pattern, long count) {System.out.println("[psubscribed]" + pattern);}@Overridepublic void message(String pattern, String channel, String message) {System.out.println("[message]" + pattern + " -> " + channel + " -> " + message);}@Overridepublic void message(String channel, String message) {System.out.println("[message]" + channel + " -> " + message);}});RedisPubSubAsyncCommands<String, String> pubsubCmd = pubsubConn.async();pubsubCmd.psubscribe("CH");pubsubCmd.psubscribe("CH2");pubsubCmd.unsubscribe("CH");Thread.sleep(100 * 5);pubsubConn.close();redisClient.shutdown();}
}

客户端资源与参数配置

        Lettuce 客户端的通信框架集成了 Netty 的非阻塞 IO 操作，客户端资源的设置与 Lettuce 的性能、并发和事件处理紧密相关，如果不是特别熟悉客户端参数配置，不建议在没有经验的前提下凭直觉修改默认值，保持默认配置就行。

        非集群环境下，具体的配置案例如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {ClientResources resources = DefaultClientResources.builder().ioThreadPoolSize(4) //I/O线程数.computationThreadPoolSize(4) //任务线程数.build();RedisURI redisUri = RedisURI.builder().withHost("127.0.0.1").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();ClientOptions options = ClientOptions.builder().autoReconnect(true)//是否自动重连.pingBeforeActivateConnection(true)//连接激活之前是否执行PING命令.build();RedisClient client = RedisClient.create(resources, redisUri);client.setOptions(options);StatefulRedisConnection<String, String> connection = client.connect();RedisCommands<String, String> commands = connection.sync();commands.set("name", "xxxx");System.out.println(commands.get("name"));connection.close();client.shutdown();resources.shutdown();}
}

        集群环境下，具体的配置案例如下：

public class LettuceMain {public static void main(String[] args) throws Exception {ClientResources resources = DefaultClientResources.builder().ioThreadPoolSize(4) //I/O线程数.computationThreadPoolSize(4) //任务线程数.build();RedisURI redisUri = RedisURI.builder().withHost("192.168.221.11").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();ClusterClientOptions options = ClusterClientOptions.builder().autoReconnect(true)//是否自动重连.pingBeforeActivateConnection(true)//连接激活之前是否执行PING命令.validateClusterNodeMembership(true)//是否校验集群节点的成员关系.build();RedisClusterClient client = RedisClusterClient.create(resources, redisUri);client.setOptions(options);StatefulRedisClusterConnection<String, String> connection = client.connect();RedisAdvancedClusterCommands<String, String> commands = connection.sync();commands.set("name", "goodss");System.out.println(commands.get("name"));connection.close();client.shutdown();resources.shutdown();}
}

线程池配置

        Lettuce 连接设计的时候，就是线程安全的，所以一个连接可以被多个线程共享，同时 lettuce 连接默认是自动重连的，使用单连接基本可以满足业务需求，大多数情况下不需要配置连接池，多连接并不会给操作带来性能上的提升。

但在某些特殊场景下，比如事物操作，使用连接池会是一个比较好的方案，那么如何配置线程池呢？

public class LettuceUtil {public static void main(String[] args) throws Exception {RedisURI redisUri = RedisURI.builder().withHost("192.168.221.11").withPort(6379).withPassword("111111").withTimeout(Duration.of(10, ChronoUnit.SECONDS)).build();RedisClient client = RedisClient.create(redisUri);//连接池配置GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();poolConfig.setMaxIdle(2);GenericObjectPool<StatefulRedisConnection<String, String>> pool = ConnectionPoolSupport.createGenericObjectPool(client::connect, poolConfig);StatefulRedisConnection<String, String> connection = pool.borrowObject();RedisCommands<String, String> commands = connection.sync();commands.set("name", "llkd");System.out.println(commands.get("name"));connection.close();pool.close();client.shutdown();}
}

主从模式配置

        redis 一般采用主从复制模式，搭建高可用的架构，简单的说就一个主节点，多个从节点，自动从主节点同步最新数据。

        Lettuce 支持自动发现主从模式下的节点信息，然后保存到本地，具体配置如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {//这里只需要配置一个节点的连接信息，不一定需要是主节点的信息，从节点也可以;可以自动发现主从节点RedisURI uri = RedisURI.builder().withHost("192.168.221.11").withPort(6379).withPassword("123456").build();RedisClient client = RedisClient.create(uri);StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uri);//从节点读取数据connection.setReadFrom(ReadFrom.REPLICA);RedisCommands<String, String> commands = connection.sync();commands.set("name", "张飞");System.out.println(commands.get("name"));connection.close();client.shutdown();}
}

        当然我们也可以手动指定集群节点来加载，具体配置如下：

public class LettuceMain {public static void main(String[] args) throws Exception {//集群节点List<RedisURI> uris = new ArrayList();uris.add(RedisURI.builder().withHost("192.168.221.14").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.15").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.16").withPort(7001).withPassword("123456").build());RedisClient client = RedisClient.create();StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uris);//从节点读取数据connection.setReadFrom(ReadFrom.REPLICA);RedisCommands<String, String> commands = connection.sync();commands.set("name", "张飞");System.out.println(commands.get("name"));connection.close();client.shutdown();}
}

哨兵模式配置

        哨兵模式，也是 redis 实现服务高可用的一大亮点，具体配置实现如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {//集群节点List<RedisURI> uris = new ArrayList();uris.add(RedisURI.builder().withHost("192.168.221.11").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.12").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.13").withPort(7000).withPassword("123456").build());RedisClient client = RedisClient.create();StatefulRedisMasterReplicaConnection<String, String> connection = MasterReplica.connect(client, StringCodec.UTF8, uris);//从节点读取数据connection.setReadFrom(ReadFrom.REPLICA);RedisCommands<String, String> commands = connection.sync();commands.set("name", "dddown");System.out.println(commands.get("name"));connection.close();client.shutdown();}
}

Cluster 集群模式配置

        Cluster 集群模式，是之后推出的一种高可用的架构模型，主要是采用分片方式来存储数据，具体配置如下：

public class LettuceUtil {public static void main(String[] args) throws Exception {Set<RedisURI> uris = new HashSet<>();uris.add(RedisURI.builder().withHost("192.168.221.11").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.12").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.13").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.14").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.15").withPort(7000).withPassword("123456").build());uris.add(RedisURI.builder().withHost("192.168.221.16").withPort(7001).withPassword("123456").build());RedisClusterClient client = RedisClusterClient.create(uris);StatefulRedisClusterConnection<String, String> connection = client.connect();RedisAdvancedClusterCommands<String, String> commands = connection.sync();commands.set("name", "uuup");System.out.println(commands.get("name"));//选择从节点,只读NodeSelection<String, String> replicas = commands.replicas();NodeSelectionCommands<String, String> nodeSelectionCommands = replicas.commands();Executions<List<String>> keys = nodeSelectionCommands.keys("*");keys.forEach(key -> System.out.println(key));connection.close();client.shutdown();}
}

小结

        Lettuce 作为 Jedis 客户端，功能更加强大，不仅解决了线程安全的问题，还支持异步和响应式编程，支持集群，Sentinel，管道和编码器等等功能。