基于Redisson 实现 Redis 分布式锁

代码示例：

    @GetMapping("/testJmeter")
    public void testJmeter() {

        synchronized (this){
            int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"))
            if (stock > 0) {
               int realStock = stock - 1;
               stringRedisTemplate.opsForValue().set("stock",realStock);
               System.out.println("扣减成功，剩余："+ realStock);
            } else {
               System.out.println("扣减失败");
            }
        }
    }

简单优化方法：

    @GetMapping("/testJmeter")
    public void testJmeter() {
      try {
      String lockKey = "lockKey";
      Boolean  result = stringRedisTempalte.opsForValue.setIfAbsent(lockKey,"zhuzhe");
      if (!result) {
         return "错误";
      } 
            int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"))
            if (stock > 0) {
               int realStock = stock - 1;
               stringRedisTemplate.opsForValue().set("stock",realStock);
               System.out.println("扣减成功，剩余："+ realStock);
            } else {
               System.out.println("扣减失败");
            }
       } finaly{
        stringRedisTempalte.delete(lockKey);
       }
    }

优化方法：

可以实现对 给这把锁加上一个过期时间

    @GetMapping("/testJmeter")
    public void testJmeter() {
      try {
      String lockKey = "lockKey";
      Boolean  result = stringRedisTempalte.opsForValue
.setIfAbsent(lockKey,"zhuzhe",10,TimeUnit.SECONDS); // 设置过期时间
      if (!result) {
         return "错误";
      } 
      int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"))
      if (stock > 0) {
          int realStock = stock - 1;
          stringRedisTemplate.opsForValue().set("stock",realStock);
          System.out.println("扣减成功，剩余："+ realStock);
      } else {
          System.out.println("扣减失败");
       }} finaly{
        stringRedisTempalte.delete(lockKey);
       }
    }

 依然会有点问题--->失效时间不好设置，其中业务逻辑出现 SQL 慢查询导致代码执行时间长，在高并发情况下，会出现删 错锁的情况。A服务把 B服务中的锁 删除了。

优化方法：

每个线程都生成一个唯一id

    @GetMapping("/testJmeter")
    public void testJmeter() {
      try {
      String lockKey = "lockKey";
      String clientId = UUID.randomUUID.totring();

      Boolean  result = stringRedisTempalte.opsForValue
.setIfAbsent(lockKey ,clientId ,10,TimeUnit.SECONDS); // 设置过期时间
      if (!result) {
         return "错误";
      } 
      int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"))
      if (stock > 0) {
          int realStock = stock - 1;
          stringRedisTemplate.opsForValue().set("stock",realStock);
          System.out.println("扣减成功，剩余："+ realStock);
      } else {
          System.out.println("扣减失败");
       }} finaly{
        if (clientId.equals(stringRedisTempalte.opsForValue.getLockKey)){
           stringRedisTempalte.delete(lockKey);
        }
       
       }
    }

最终解决方法：

引入 Redission 依赖

<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson</artifactId>
    <version>3.6.5</version>
</dependency>

配置：

@Configuration
public class RedissonConfig {
 
    @Value("${spring.redis.host}")
    private String address;
    @Value("${spring.redis.port}")
    private String port;
    @Value("${spring.redis.password}")
    private String password;
 
    @Bean
    public RedissonClient redissonClient() {
        Config config = new Config();
        //此处为单机模式  （注：有多种模式）
        config.useSingleServer()
                .setAddress("redis://" + address + ":"+port)
                .setPassword(password)
                .setTimeout(10000)
                .setRetryAttempts(5)
                .setRetryInterval(2000)
                .setConnectionPoolSize(64)
                .setConnectionMinimumIdleSize(24)
                // 保持连接活动
                .setKeepAlive(true)
                // 发送PING命令的间隔时间;
                .setPingConnectionInterval(30000);
 
        return Redisson.create(config);
    }
}

 代码示例：

@Rescourse
private Redisson redisson;

    @GetMapping("/testJmeter")
    public void testJmeter() {
      try {
      String lockKey = "lockKey";
      String clientId = UUID.randomUUID.totring();
      
      //获取锁
      Rlock redissonLock = redisson.getLock(lockkey);


      //Boolean  result = stringRedisTempalte.opsForValue
.setIfAbsent(lockKey ,clientId ,10,TimeUnit.SECONDS); // 设置过期时间
      //if (!result) {
       //  return "错误";
     // } 
      //加锁
      redissonLock.lock()
       
      int stock = Integer.parseInt(stringRedisTemplate.opsForValue().get("stock"))
      if (stock > 0) {
          int realStock = stock - 1;
          stringRedisTemplate.opsForValue().set("stock",realStock);
          System.out.println("扣减成功，剩余："+ realStock);
      } else {
          System.out.println("扣减失败");
       }} finaly{
          //释放锁
          redissonLock.unlock()
       // if (clientId.equals(stringRedisTempalte.opsForValue.getLockKey)){
           
      
           //stringRedisTempalte.delete(lockKey);
        }
       
       }
    }