public SendResult send(
    Message msg) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
    return send(msg, this.defaultMQProducer.getSendMsgTimeout());
}

public SendResult send(Message msg,
    long timeout) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {
    return this.sendDefaultImpl(msg, CommunicationMode.SYNC, null, timeout);
}

private SendResult sendDefaultImpl(
    Message msg,
    final CommunicationMode communicationMode,
    final SendCallback sendCallback,
    final long timeout
) throws MQClientException, RemotingException, MQBrokerException, InterruptedException {}

//校驗(yàn)生產(chǎn)者服務(wù)是ok的，可以聯(lián)系到的
this.makeSureStateOK();
//校驗(yàn)消息的參數(shù)
Validators.checkMessage(msg, this.defaultMQProducer);

private void makeSureStateOK() throws MQClientException {
    if (this.serviceState != ServiceState.RUNNING) {
        throw new MQClientException("The producer service state not OK, "
            + this.serviceState
            + FAQUrl.suggestTodo(FAQUrl.CLIENT_SERVICE_NOT_OK),
            null);
    }
}

public static void checkMessage(Message msg, DefaultMQProducer defaultMQProducer) throws MQClientException {
    if (null == msg) {
        throw new MQClientException(ResponseCode.MESSAGE_ILLEGAL, "the message is null");
    }
    // 這里校驗(yàn)Topic的時(shí)候，校驗(yàn)了不能為空，長(zhǎng)度和特殊字符
    Validators.checkTopic(msg.getTopic());
    //這里則校驗(yàn)了一些不允許使用的topic名字
    Validators.isNotAllowedSendTopic(msg.getTopic());
    // body不為空
    if (null == msg.getBody()) {
        throw new MQClientException(ResponseCode.MESSAGE_ILLEGAL, "the message body is null");
    }
    // body長(zhǎng)度不為0
    if (0 == msg.getBody().length) {
        throw new MQClientException(ResponseCode.MESSAGE_ILLEGAL, "the message body length is zero");
    }
    // body 長(zhǎng)度不能過(guò)長(zhǎng)
    if (msg.getBody().length > defaultMQProducer.getMaxMessageSize()) {
        throw new MQClientException(ResponseCode.MESSAGE_ILLEGAL,
            "the message body size over max value, MAX: " + defaultMQProducer.getMaxMessageSize());
    }
}

TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic());

private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) {
    //獲取topic信息
    TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic);
    //不存在
    if (null == topicPublishInfo || !topicPublishInfo.ok()) {
        //新建
        this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo());
        //修改topic的路由信息并更新到本地
        this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic);
        topicPublishInfo = this.topicPublishInfoTable.get(topic);
    }
    //包含路由信息就直接返回
    if (topicPublishInfo.isHaveTopicRouterInfo() || topicPublishInfo.ok()) {
        return topicPublishInfo;
    } else {
        //不包含路由信息則向name server申請(qǐng)，修改topic的路由信息并更新到本地
        this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer);
        topicPublishInfo = this.topicPublishInfoTable.get(topic);
        return topicPublishInfo;
    }
}

int timesTotal = communicationMode == CommunicationMode.SYNC ? 1 + this.defaultMQProducer.getRetryTimesWhenSendFailed() : 1;

MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName);

sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout - costTime);