【Redis】Redis 的学习教程（三）之 Lettuce

柔光的暖阳◎ 2023-10-14 16:06 14阅读 0赞

Lettuce 是 Redis 的一款高级 Java 客户端，与 Jedis 并列成为最热门的客户端之一，目前已成为 SpringBoot 2.0 版本默认的 redis 客户端

官网地址：[Lettuce 官网][Lettuce]

相比老牌 Jedis，Lettuce 属于后起之秀，不仅功能丰富，而且提供了很多新的功能特性，比如异步操作、响应式编程等等，同时还解决了 Jedis 中线程不安全的问题。

## 1. 集成 Lettuce ##

1、引入依赖：

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

2、测试：

## 2. 常用操作 ##

### 2.1 同步操作 ###

基本上只要是 Jedis 支持的同步命令操作，Lettuce 都支持。

下面，我们以同步操作字符串为例，Lettuce 的 api 操作如下：

public class LettuceMain {
        
    
        public static void main(String[] args) {
        
            RedisURI redisUri = RedisURI.builder()
                    .withHost("127.0.0.1").withPort(6379)
                    .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();
        }
    
    }

### 2.2 异步操作 ###

除此之外，Lettuce 还支持异步操作

RedisAsyncCommands<String, String> commands = connection.async();

### 2.3 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/`

public class LettuceMain {
        
    
        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1
            commands.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();
        }
    }

### 2.4 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 LettuceReactiveMain1 {
        
    
        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>() {
        
                @Override
                public void unsubscribed(String channel, long count) {
        
                    System.out.println("[unsubscribed]" + channel);
                }
                @Override
                public void subscribed(String channel, long count) {
        
                    System.out.println("[subscribed]" + channel);
                }
                @Override
                public void punsubscribed(String pattern, long count) {
        
                    System.out.println("[punsubscribed]" + pattern);
                }
                @Override
                public void psubscribed(String pattern, long count) {
        
                    System.out.println("[psubscribed]" + pattern);
                }
                @Override
                public void message(String pattern, String channel, String message) {
        
                    System.out.println("[message]" + pattern + " -> " + channel + " -> " + message);
                }
                @Override
                public 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();
        }
    }

### 2.5 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：

### 2.6 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 LettuceMain {
        
    
        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("192.168.31.111").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("192.168.31.111").withPort(6379).withPassword("111111").build());
            uris.add(RedisURI.builder().withHost("192.168.31.112").withPort(6379).withPassword("111111").build());
            uris.add(RedisURI.builder().withHost("192.168.31.113").withPort(6379).withPassword("111111").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();
        }
    }

### 2.7 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 LettuceMain {
        
    
        public static void main(String[] args) throws Exception {
        
            //集群节点
            List<RedisURI> uris = new ArrayList();
            uris.add(RedisURI.builder().withSentinel("192.168.31.111", 26379).withSentinelMasterId("mymaster").withPassword("123456").build());
            uris.add(RedisURI.builder().withSentinel("192.168.31.112", 26379).withSentinelMasterId("mymaster").withPassword("123456").build());
            uris.add(RedisURI.builder().withSentinel("192.168.31.113", 26379).withSentinelMasterId("mymaster").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", "赵云");
            System.out.println(commands.get("name"));
    
            connection.close();
            client.shutdown();
        }
    }

### 2.8 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 LettuceReactiveMain4 {
        
    
        public static void main(String[] args) throws Exception {
        
            Set<RedisURI> uris = new HashSet<>();
            uris.add(RedisURI.builder().withHost("192.168.31.111").withPort(7000).withPassword("123456").build());
            uris.add(RedisURI.builder().withHost("192.168.31.112").withPort(7000).withPassword("123456").build());
            uris.add(RedisURI.builder().withHost("192.168.31.113").withPort(7000).withPassword("123456").build());
            uris.add(RedisURI.builder().withHost("192.168.31.114").withPort(7000).withPassword("123456").build());
            uris.add(RedisURI.builder().withHost("192.168.31.115").withPort(7000).withPassword("123456").build());
            uris.add(RedisURI.builder().withHost("192.168.31.116").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", "关羽");
            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();
        }
    }

Lettuce 相比老牌的 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。

[Lettuce]: https://lettuce.io/