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附源码！Spring Boot 并发登录人数控制

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作者 | 殷天文

链接 | www.jianshu.com/p/b6f5ec98d790

上篇 | 3 5 个小细节，提升 Java 代码运行效率

通常系统都会限制同一个账号的登录人数，多人登录要么限制后者登录，要么踢出前者，Spring Security 提供了这样的功能，本文讲解一下在没有使用Security的时候如何手动实现这个功能

demo 技术选型

SpringBoot
JWT
Filter
Redis + Redisson

JWT（token）存储在Redis中，类似 JSessionId-Session的关系，用户登录后每次请求在Header中携带jwt

如果你是使用session的话，也完全可以借鉴本文的思路，只是代码上需要加些改动

两种实现思路

比较时间戳

维护一个 username: jwtToken 这样的一个 key-value 在Reids中, Filter逻辑如下

附源码！Spring Boot 并发登录人数控制

public class CompareKickOutFilter extends KickOutFilter {

    @Autowired
    private UserService userService;

    @Override
    public boolean isAccessAllowed(HttpServletRequest request, HttpServletResponse response){
        String token = request.getHeader("Authorization");
        String username = JWTUtil.getUsername(token);
        String userKey = PREFIX + username;

        RBucket<String> bucket = redissonClient.getBucket(userKey);
        String redisToken = bucket.get();

        if (token.equals(redisToken)) {
            return true;

        } else if (StringUtils.isBlank(redisToken)) {
            bucket.set(token);

        } else {
            Long redisTokenUnixTime = JWTUtil.getClaim(redisToken, "createTime").asLong();
            Long tokenUnixTime = JWTUtil.getClaim(token, "createTime").asLong();

            // token > redisToken 则覆盖
            if (tokenUnixTime.compareTo(redisTokenUnixTime) > 0) {
                bucket.set(token);

            } else {
                // 注销当前token
                userService.logout(token);
                sendJsonResponse(response, 4001, "您的账号已在其他设备登录");
                return false;

            }

        }

        return true;

    }
}

队列踢出

附源码！Spring Boot 并发登录人数控制

public class QueueKickOutFilter extends KickOutFilter {
    /**
     * 踢出之前登录的/之后登录的用户 默认踢出之前登录的用户
     */
    private boolean kickoutAfter = false;
    /**
     * 同一个帐号最大会话数 默认1
     */
    private int maxSession = 1;

    public void setKickoutAfter(boolean kickoutAfter) {
        this.kickoutAfter = kickoutAfter;
    }

    public void setMaxSession(int maxSession) {
        this.maxSession = maxSession;
    }

    @Override
    public boolean isAccessAllowed(HttpServletRequest request, HttpServletResponse response) throws Exception {
        String token = request.getHeader("Authorization");
        UserBO currentSession = CurrentUser.get();
        Assert.notNull(currentSession, "currentSession cannot null");
        String username = currentSession.getUsername();
        String userKey = PREFIX + "deque_" + username;
        String lockKey = PREFIX_LOCK + username;

        RLock lock = redissonClient.getLock(lockKey);

        lock.lock(2, TimeUnit.SECONDS);

        try {
            RDeque<String> deque = redissonClient.getDeque(userKey);

            // 如果队列里没有此token，且用户没有被踢出；放入队列
            if (!deque.contains(token) && currentSession.isKickout() == false) {
                deque.push(token);
            }

            // 如果队列里的sessionId数超出最大会话数，开始踢人
            while (deque.size() > maxSession) {
                String kickoutSessionId;
                if (kickoutAfter) { // 如果踢出后者
                    kickoutSessionId = deque.removeFirst();
                } else { // 否则踢出前者
                    kickoutSessionId = deque.removeLast();
                }

                try {
                    RBucket<UserBO> bucket = redissonClient.getBucket(kickoutSessionId);
                    UserBO kickoutSession = bucket.get();

                    if (kickoutSession != null) {
                        // 设置会话的kickout属性表示踢出了
                        kickoutSession.setKickout(true);
                        bucket.set(kickoutSession);
                    }

                } catch (Exception e) {
                }

            }

            // 如果被踢出了，直接退出，重定向到踢出后的地址
            if (currentSession.isKickout()) {
                // 会话被踢出了
                try {
                    // 注销
                    userService.logout(token);
                    sendJsonResponse(response, 4001, "您的账号已在其他设备登录");

                } catch (Exception e) {
                }

                return false;

            }

        } finally {
            if (lock.isHeldByCurrentThread()) {
                lock.unlock();
                LOGGER.info(Thread.currentThread().getName() + " unlock");

            } else {
                LOGGER.info(Thread.currentThread().getName() + " already automatically release lock");
            }
        }

        return true;
    }

}