Redisson 使用读写锁解决缓存一致性问题

小半 • 2022年12月29日下午10:44 • 后端开发 • 阅读 536

1.前置条件项目里集成了redisson

controller 层

//查询
    @GetMapping("/getUserById/{id}")
    public Result getUserById(@PathVariable("id")Integer id) {
        User user = userService.getUserById(id);
        return Result.ok(UserCovertBasic.INSTANCE.toConvertUserVO(user));
    }
//更新
   @RequestMapping(value = "/updateUser")
    public Result updateUser(@RequestBody @Validated UserUpdateDTO userUpdateDTO) throws Exception {

        Long userId = userUpdateDTO.getId();
        User user = userService.getById(userId);
        if (BeanUtil.isEmpty(user)){
            throw new Exception("用户不存在");
        }
        BeanUtils.copyProperties(userUpdateDTO,user);
        userService.updateByUser(user);
        return Result.ok();
    }

service层

public interface IUserService extends IService<User> {

    User getUserById(Integer id);

    void updateByUser(User user);
}

service impl层

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IUserService {

    public final String CACHE_USER_BY_ID = "CACHE_USER_BY_ID";
    @Resource
    private RedisUtils redisUtils;
    @Resource
    private RedissonClient redissonClient;

     @Override
    public User getUserById(Integer id) {
        String idStr = String.valueOf(id);
        String lockKey = CACHE_USER_BY_ID.concat(idStr);
        RReadWriteLock lock = redissonClient.getReadWriteLock(lockKey);
        //查询的时候使用共享读锁
        RLock readLock = lock.readLock();
        readLock.lock();
        User user = null;
        try {
            if (redisUtils.hHasKey(CACHE_USER_BY_ID, idStr)) {
                String cache = JSONUtil.toJsonStr(redisUtils.hget(CACHE_USER_BY_ID, idStr));
                return JSON.parseObject(cache, User.class);
            }
            user = this.getById(id);
            if (null != user) {
                redisUtils.hset(CACHE_USER_BY_ID, idStr, JSONUtil.toJsonStr(user));
            }
        } finally {
            if (readLock.isLocked() && readLock.isHeldByCurrentThread()) {
                readLock.unlock(); //解锁
            }
        }
        return user;
    }

    @Override
    public void updateByUser(User user) {
        String idStr = String.valueOf(user.getId());
        String lockKey = CACHE_USER_BY_ID.concat(idStr);
       //获取redisson 读写锁
        RReadWriteLock lock = redissonClient.getReadWriteLock(lockKey);
        //更新时使用独占写锁
        RLock rLock = lock.writeLock();
        rLock.lock();
        try {
            this.updateById(user);
            redisUtils.hset(CACHE_USER_BY_ID, idStr, JSONUtil.toJsonStr(user));
        } finally {
            if (rLock.isLocked() && rLock.isHeldByCurrentThread()) {
                rLock.unlock(); //3. 解锁
            }
        }
    }
}