Java中对于并发问题的处理思路分享

public void addOrder() {
    // 1.获取当前年月日以及商户标识
    String currentDate = "yyyyMMddHHmmss";
    String businessman = "商户标识";
    // 2.获取获取序列号
    long index = getIndex();
    // 3.拼接订单号
    String orderNum = businessman + currentDate + index;
    // 4.生成订单
    save(订单对象);
}

public String getIndex() {
    // 根据算法生成唯一序列号
    return buildIndexUtils.build();
}

public String getIndex() {
    // 1.获取当前商户、当前单据已生成的最大序列号
    Integer index = dao.getIndex(商户, 单据) + 1;
    // 2.序列号 + 1
    index = index++;
    // 3.修改当前商户、当前单据已生成的最大序列号
    dao.update(商户, 单据, index);
    // 4.返回序列号
    return index + "";
}

/**
 * @param id     数据ID
 * @param status 数据的状态
 */
public void update(Long id, Integer status) {
    // 1.根据ID查询数据
    PO po = dao.select(id);
    // 2.判断数据的状态是否符合修改要求(这一步主要是应对两个线程都进入Controller层，其中线程1刚好提交事务后，线程2开始事务的情况)
    if(!status.equals(po.getStatus())) {
        throw new TJCException("数据已被修改，请刷新后重试");
    }
    // 3.修改数据(启用乐观锁机制，主要应对线程1提交事务之前线程2开启事务的情况)
    int i = dao.update("update table set xxx = ?, version = version + 1 where id = ? and version > ?");
    if(i == 0) {
        throw new TJCException("数据已被修改，请刷新后重试");
    }
    // 继续执行下面业务
}

// 上游服务发送消息
public void request() {
    String messageId = "xxxx";
    rpc.request(messageId, message);
}

// 下游服务消费消息
public void consume(String messageId, String message) {
    // 将messageId存储在redis中, 单机环境也可以直接找个map去存或者存在Guava中
    Boolean flag = stringRedisTemplate.opsForValue()
                .setIfAbsent(messageId, "1", 60, TimeUnit.SECONDS);
    if(!flag) {
       log.error("重复消息拦截");
       return;
    }
    // 继续执行下面业务
     .....
    // 事务完成后(提交/回滚)，删除标识
    TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
        @Override
        public void afterCompletion(int status) {
            stringRedisTemplate.delete(messageId);
        }
    });
}

// 序列号的key可以设置为(模块名:orderIndex:订单类型:yyyyMMdd)
String dateFormat = getCurrentDateFormat("yyyyMMdd");
// key
String key = 模块名 + ":" + orderIndex + ":" + 订单类型 + ":" + dateFormat;
String script = "if (redis.call('exists', KEYS[1]) == 0) then redis.call('setex', KEYS[1], ARGV[1], ARGV[2]) return 1 else return redis.call('incr', KEYS[1]) end";
DefaultRedisScript<Long> defaultRedisScript = new DefaultRedisScript<>();
defaultRedisScript.setResultType(Long.class);
defaultRedisScript.setScriptText(script);
long count = stringRedisTemplate.execute(defaultRedisScript, Arrays.asList(key), (3600 * 24) + "", "1");

/**
 * @param indexStdId         标准ID
 * @param currentTeamClassId 班ID
 * @param dataId             数据ID
 * @param count              计数要求
 */
public List<Long> countMonitor(Long indexStdId, Long currentTeamClassId, Long 
dataId, Integer count) {
        StringBuilder countMonitorLua = new StringBuilder();
        countMonitorLua.append("if (redis.call('hget', KEYS[1], KEYS[2]) == ARGV[2]) ");
        countMonitorLua.append("then ");
        countMonitorLua.append("    if (redis.call('hget', KEYS[1], KEYS[3]) == ARGV[3]) ");
        countMonitorLua.append("    then ");
        countMonitorLua.append("        redis.call('hset', KEYS[1], KEYS[3], 0) ");
        countMonitorLua.append("        redis.call('lpush', KEYS[4], ARGV[1]) ");
        countMonitorLua.append("        local list = redis.call('lrange', KEYS[4], 0, -1) ");
        countMonitorLua.append("        redis.call('del', KEYS[4]) ");
        countMonitorLua.append("        return list ");
        countMonitorLua.append("    else ");
        countMonitorLua.append("        redis.call('lpush', KEYS[4], ARGV[1]) ");
        countMonitorLua.append("        redis.call('hincrby', KEYS[1], KEYS[3], 1) ");
        countMonitorLua.append("        return {} ");
        countMonitorLua.append("    end ");
        countMonitorLua.append("else ");
        countMonitorLua.append("    redis.call('del', KEYS[4]) ");
        countMonitorLua.append("    redis.call('lpush', KEYS[4], ARGV[1]) ");
        countMonitorLua.append("    redis.call('hset', KEYS[1], KEYS[3], 1) ");
        countMonitorLua.append("    redis.call('hset', KEYS[1], KEYS[2], ARGV[2]) ");
        countMonitorLua.append("    if (redis.call('hget', KEYS[1], KEYS[3]) == ARGV[4]) ");
        countMonitorLua.append("    then ");
        countMonitorLua.append("        redis.call('hset', KEYS[1], KEYS[3], 0) ");
        countMonitorLua.append("        local list2 = redis.call('lrange', KEYS[4], 0, -1) ");
        countMonitorLua.append("        redis.call('del', KEYS[4]) ");
        countMonitorLua.append("        return list2 ");
        countMonitorLua.append("    else ");
        countMonitorLua.append("        return {} ");
        countMonitorLua.append("    end ");
        countMonitorLua.append("end ");

        DefaultRedisScript<List> defaultRedisScript = new DefaultRedisScript<>();
        defaultRedisScript.setResultType(List.class);
        defaultRedisScript.setScriptText(countMonitorLua.toString());
        List<String> keys = new ArrayList<>();
        keys.add(COUNTMONITOR_HASH.replace("${indexStd}", indexStdId.toString()));
        keys.add(COUNTMONITOR_HASH_CURRENTTEAMCLASSID);
        keys.add(COUNTMONITOR_HASH_COUNT);
        keys.add(COUNTMONITOR_LIST.replace("${indexStd}", indexStdId.toString()));
        List dataIdList = stringRedisTemplate.execute(defaultRedisScript, keys, gapDataId.toString(), currentTeamClassId.toString(), (count - 1) + "", count + "");

        List<Long> collect = null;
        if(!gapDataIdList.isEmpty()) {
            collect = (List<Long>) gapDataIdList.stream().map(o -> Long.valueOf(o.toString())).collect(Collectors.toList());
        }
        return collect;
    }