关于wesocket大文件通讯的切片实现方法

关于websocket的实现网上很多资料这里就不详说，这里大概讲我在websocket传输大文件的时的方法，websocket传输单个文件最大不能超过7kg，否则前段自动断掉，当我们用来语音通讯时，通常语音文件都比较大，传输单个语音文件显然是不现实的，网上查了关于微信的语音实现，当然具体的源码是看不到的，不过有人亲测过微信语音大概的实现过程。

微信实现语音的过程是边录音边传输，把一段语音切割成很多个小片段的语音传输到后台，后台在进行合并处理，后台向前段传输语音时同理，我的项目中大概实现如下：

前段用recorder.js实现浏览器录音，录音完成后得到语音文件为blob，blob是js里的一个大文件对象，是原始二进制数据，实现为

var blob = new Blob(chuanks[],{type:"audio/wav"});

其中chuanks[]可以示多种数据类型，arraybuffer，blob等，我的实现方法是把blob大文件通过bolb.slice()切割成多个小blob文件，然后用

var reader = new FileReader();把文件转成base64传输到后台合并处理，blob文件只能通过FileReader对象来读取文件内容，下面直接上代码

   //前台
   recorder && recorder.exportWAV(function(blob) {
      //将文件转为base64
        console.log(blob);
        var type = "audio/wav";
        var chunk = 5 * 1024;
        var messageid = new Date().toISOString() + RndNum(5);
        var chunks = [];
        var start = 0;
        var islast = false;
        //文件切割
        for (var i = 0; i < Math.ceil(blob.size / chunk); i++) {
            var end = start + chunk;
            chunks[i] = blob.slice(start , end, type);
            start = end;
            if(blob.size<end){islast=true;}
            send(chunks[i], type, messageid, i, islast);
        }   
    //发送文件
    function send(val,type, messageid, i, islast){
            var reader = null;
            var postValue={}
            reader = new FileReader()
            reader.readAsDataURL(val,"UTF-8");//转成base64
            reader.onload = function () {
                str = reader.result.split(",")[1];
                postValue.voicetype=type;
                postValue.content=str;
                postValue.messageid=messageid;
                postValue.sequence=i;
                postValue.islast=islast;
                socket.send(JSON.stringify(postValue));//websocket发送文件
                
            };
        
    }

//后台接收

String messageId = req.getMessageid();
boolean isLast = req.isIslast();
int sequence = req.getSequence();
String content = req.getContent();
org.json.JSONObject result = null;
try {
    SplitMessage saveMessage = spiltmessages.get(messageId);
    if(isLast==true && saveMessage==null ) {
        result  = BaiduIntelligeVoiceUtil.asr(content,req.getVoicetype());
    }else{
        if((saveMessage==null ||saveMessage.getContent()==null) && isLast==false && sequence==0){
            byte[] splitBytes = Base64Utils.decodeFromString(content);
            SplitMessage splitMessageNew = new SplitMessage(sequence,splitBytes);
            spiltmessages.put(messageId,splitMessageNew);
            return;
        }else if(saveMessage !=null && saveMessage.getContent()!=null && isLast==false){
            byte[] saveContent = saveMessage.getContent();
            if((sequence)!=saveMessage.getSequence()+1){
                SimpleResponse simpleResponse = SimpleResponse.failureResp("接收语音文件格式转化时发生错误","text");
                return;
            }
            byte[] splitBytes = Base64Utils.decodeFromString(content);
            //新保存的字节数组
            byte[] saveBytesNew = new byte[splitBytes.length+saveContent.length];
            System.arraycopy(saveContent,0,saveBytesNew,0,saveContent.length);
            System.arraycopy(splitBytes, 0, saveBytesNew, saveContent.length, splitBytes.length);
            saveMessage.setContent(saveBytesNew);
            saveMessage.setSequence(sequence);
            return;
        }else if(saveMessage !=null && saveMessage.getContent()!=null && isLast==true){
            if((sequence-1)!=saveMessage.getSequence()){
                SimpleResponse simpleResponse = SimpleResponse.failureResp("接收语音文件格式转化时发生错误","text");
                sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
                return;
            }
            byte[] saveContent = saveMessage.getContent();
            byte[] splitBytes = Base64Utils.decodeFromString(content);
            //新保存的字节数组
            byte[] saveBytesNew = new byte[splitBytes.length+saveContent.length];
            System.arraycopy(saveContent,0,saveBytesNew,0,saveContent.length);
            System.arraycopy(splitBytes, 0, saveBytesNew, saveContent.length, splitBytes.length);
            spiltmessages.remove(messageId);

            //TODO 解析语音成文字
            result = BaiduIntelligeVoiceUtil.asrForSplit(saveBytesNew,"pcm",16000,null);
        }else {
            SimpleResponse simpleResponse = SimpleResponse.failureResp("对不起，不能解析您的语音","text");
            sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
            return;
        }
    }

}catch (IOException e){
    logger.error("clientId为 :"+clientId + " 的用户语音文件格式转化时发生错误 : " + e.toString());
    SimpleResponse simpleResponse = SimpleResponse.failureResp("语音文件格式转化时发生错误","text");
    sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
    return;
} catch (InterruptedException e) {
    logger.error("clientId为 :"+clientId + " 的用户语音文件格式转化时发生错误 : " + e.toString());
    SimpleResponse simpleResponse = SimpleResponse.failureResp("语音文件格式转化时发生错误","text");
    sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
    return;
}

后台发送
//TODO 合成回答语音
                TtsResponse syncResp = BaiduIntelligeVoiceUtil.synthesis(respmessage);
                byte[] bytes = syncResp.getData();
                if(bytes!=null){
                    List<byte[]> byteList = ByteMergeAndSplitUtil.splitBytesBySize(bytes,5120);

                    for(int i=0;i<byteList.size();i++){
                        String spilitMsg = Base64Utils.encodeToString(byteList.get(i));
                        SimpleResponse simpleResponse = SimpleResponse.successResp(spilitMsg,"mp3");
                        simpleResponse.setMessageid(messageId);
                        simpleResponse.setSequence(i);
                        if(i<byteList.size()-1) {
                            sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
                        }else {
                            simpleResponse.setIslast(true);
                            simpleResponse.setVoicetotext(question);
                            sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
                        }
                    }
                    return;

                }else {
                    SimpleResponse simpleResponse = SimpleResponse.failureResp("语音合成失败", "text");
                    sendMessageToUser(clientId, new TextMessage(JSONObject.toJSONString(simpleResponse)));
                    return;
                }

//前台接收信息
    var chunks = [];
    socket.onmessage = function (msg) {
        console.log(msg.data);
        var str = {};
        var reVal = JSON.parse(msg.data);
            str.content = reVal.content;
            str.errno = reVal.errno;
            str.islast = reVal.islast;
            str.sequence = reVal.sequence;
            str.type = reVal.type;
            chunks[reVal.sequence] = base64ToBlob(str.content);
            if(str.islast){
                var blob = new Blob(chunks,{type : reVal.type});
                var url = URL.createObjectURL(blob);
                var voi = document.getElementById('voi');
                var au = document.createElement('audio');
                var div = document.createElement('div');
                  
                au.controls = true;
                au.src = url;
                voi.appendChild(div);
                div.appendChild(au);
                div.style = "float:left;clear:both;";
                voi.scrollTop = voi.scrollHeight;//使滚动条一直在底部
                openPage(reVal.voicetotext);
            }
        
        
    }

 借鉴https://segmentfault.com/a/1190000011563430