44.【面试宝典】面试宝典-redis分布式锁

public static void wrongGetLock1(Jedis jedis, String lockKey, 
String requestId, int expireTime) {
Long result = jedis.setnx(lockKey, requestId);
if (result == 1) {
// 若在这里程序突然崩溃，则无法设置过期时间，将发生死锁
jedis.expire(lockKey, expireTime);
}
}

String lua_scripts = "if redis.call('setnx',KEYS[1],ARGV[1]) == 1 then" +             
" redis.call('expire',KEYS[1],ARGV[2]) return 1 else return 0 end";  
Object result = jedis.eval(lua_scripts, 
Collections.singletonList(key_resource_id), 
Collections.singletonList(values));
//判断是否成功 return result.equals(1L);

redission支持多种连接模式
//单机
RedissonClient redisson = Redisson.create();
Config config = new Config();
config.useSingleServer().setAddress("myredisserver:6379");
RedissonClient redisson = Redisson.create(config);
//主从
Config config = new Config();
config.useMasterSlaveServers()
    .setMasterAddress("127.0.0.1:6379")
    .addSlaveAddress("127.0.0.1:6389", "127.0.0.1:6332", "127.0.0.1:6419")
    .addSlaveAddress("127.0.0.1:6399");
RedissonClient redisson = Redisson.create(config);
//哨兵
Config config = new Config();
config.useSentinelServers()
    .setMasterName("mymaster")
    .addSentinelAddress("127.0.0.1:26389", "127.0.0.1:26379")
    .addSentinelAddress("127.0.0.1:26319");
RedissonClient redisson = Redisson.create(config);
//集群
Config config = new Config();
config.useClusterServers()
    .setScanInterval(2000) // cluster state scan interval in milliseconds
    .addNodeAddress("127.0.0.1:7000", "127.0.0.1:7001")
    .addNodeAddress("127.0.0.1:7002");
RedissonClient redisson = Redisson.create(config);
下面直接贴代码,这里使用的是单机模式，切换自己改一下连接模式就行：
1.导入依赖：
<!-- org.redisson/redisson 分布式专用-->
        <dependency>
            <groupId>org.redisson</groupId>
            <artifactId>redisson</artifactId>
            <version>3.16.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
            <version>2.5.3</version>
        </dependency>
2.编写配置类：
@SpringBootApplication
public class RedisLockApplication {
    public static void main(String[] args) {
        SpringApplication.run(RedisLockApplication.class, args);
    }
    @Bean
    public Redisson redisson(){
        // 单机模式
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379").setDatabase(0);
        return (Redisson) Redisson.create(config);
    }
}
3.上锁
RLock lock = redisson.getLock("anyLock");
try {
        //1. 具有Watch Dog 自动延期机制 默认续30s 每隔30/3=10 秒续到30s
        //lock.lock();
        // 2. 支持过期解锁功能, 无需调用unlock方法手动解锁,没有Watch Dog ，10s后自动释放
        //lock.lock(10, TimeUnit.SECONDS);
        // 3. 尝试拿锁10s后停止重试,返回false 具有Watch Dog 自动延期机制 默认续30s
        //有版本区分3.16以后有三个参数，第二个参数为-1
        //lock.tryLock(10,-1, TimeUnit.SECONDS); ；即不设置过期时间，自动续期
        //boolean res1 = lock.tryLock(10, TimeUnit.SECONDS); 
       // 4.尝试加锁，最多等待10秒，上锁以后100秒自动解锁,尝试拿锁10s后停止重试,返回false 
       //没有Watch Dog ，100s后过期自动释放
        boolean res2 = lock.tryLock(10, 100, TimeUnit.SECONDS);
    if (res) { // 成功
        // do your business
    }
} catch (InterruptedException e) {
    e.printStackTrace();
} finally {
    lock.unlock();
}