使用java+springboot+springaop+redis+自定义注解，写一个分布式锁

可以使用 Redisson 实现分布式锁，具体实现如下：

1. 引入 Redisson 依赖：

<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson-spring-boot-starter</artifactId>
    <version>3.16.1</version>
</dependency>

2. 定义自定义注解 `DistributedLock`：

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DistributedLock {
    String value() default "";
    long leaseTime() default 30L;
    TimeUnit timeUnit() default TimeUnit.SECONDS;
}

3. 在需要加锁的方法上加上 `@DistributedLock` 注解：

@Service
public class UserService {
    @DistributedLock("user:#{#userId}")
    public User getUserById(String userId) {
        // ...
    }
}

4. 实现 `DistributedLockAspect` 切面：

@Aspect
@Component
public class DistributedLockAspect {
    private final RedissonClient redissonClient;

    public DistributedLockAspect(RedissonClient redissonClient) {
        this.redissonClient = redissonClient;
    }

    @Around("@annotation(distributedLock)")
    public Object around(ProceedingJoinPoint joinPoint, DistributedLock distributedLock) throws Throwable {
        String lockKey = distributedLock.value();
        if (StringUtils.isEmpty(lockKey)) {
            lockKey = joinPoint.getSignature().toLongString();
        }
        RLock lock = redissonClient.getLock(lockKey);
        boolean locked = lock.tryLock(distributedLock.leaseTime(), distributedLock.timeUnit());
        if (!locked) {
            throw new RuntimeException("获取分布式锁失败");
        }
        try {
            return joinPoint.proceed();
        } finally {
            lock.unlock();
        }
    }
}

5. 在 `application.yml` 中配置 Redisson：

spring:
  redis:
    host: localhost
    port: 6379
    password:
    database: 0
redisson:
  single-server-config:
    address: redis://${spring.redis.host}:${spring.redis.port}

这样就实现了一个基于 Redis 的分布式锁。