Node.js Http 写入结束后

我在 node.js 中编写了一个简单的 CRUD Api。我的所有 POST、PUT 和 DELETE 函数都在结束后不断写入。我已经完全失去了尝试拍摄这件事的感觉，并希望有一双新的眼睛或一些关于试图追踪它的建议。GET 工作得很好，并且在 httpmgs.js 中使用了相同的代码 sendJSON()。

我散布了各种各样的评论，试图找出错误发生的地方。我不知道 req.on("end".... 是否引起了问题，所以我重写了那部分无济于事。

控制器.js：

 switch (req.method){
    case "GET":
          if(req.url === "/staff"){
            staff.getList(req, resp);
        }
        break;
    case "POST":
      if (req.url === "/staff/add"){
            var reqBody = '';
            req.on("data", function (data){
                reqBody += data;
                if(reqBody.length > 1e7){
                    msg.show413(req, resp);              
                }
            });
            req.on("end", function() {
                console.log(req.data)
                staff.add(req, resp, reqBody)
            });            
        }
        break;
    case "PUT":
        if (req.url === "/staff/update"){
            var reqBody = '';
            req.on("data", function (data){
                reqBody += data;
                if(reqBody.length > 1e7){
                    msg.show413(req, resp);
                }
            });
            req.on("end", function() {
                staff.update(req, resp, reqBody);
            });

        }
        else{
            msg.show404(req,resp);
        }
        break;

工作人员.js：

exports.add = function (req, resp, reqBody){
    try{
        if (!reqBody) throw new Error("Input not valid");
        var data = JSON.parse(reqBody);
        if (data){

            db.executeSql("SELECT MAX(ID) AS ID FROM jarvisdb.staff",function (maxID, err){
                if(err){
                    msg.show500(req, resp, err);
                }
                else{
                    var newID = maxID[0].ID+1
                    var sql = "INSERT INTO jarvisdb.staff (`ID`, `First Name`, `Last Name`) VALUES";
                    sql+= util.format("('%d' ,\"%s\", \"%s\")", newID, data.firstName, data.lastName); 
                    db.executeSql(sql, (data, err)=>{
                        if(err){
                            msg.show500(req, resp, err)
                        }
                        else{
                            console.log('Before send')
                            msg.sendJSON(req,resp,data)
                            console.log('After send')
                        }
                    })

                }
            });
        }
        else{
            throw new Error("Input not valid");
        }
    }
    catch (ex) {
        console.log('500')
        msg.show500(req, resp, ex);

    }
};

httpMsgs.js：

exports.sendJSON = function(req,resp,data){
    if(data){
        console.log('Before Write')
        resp.writeHead(200, {"Content-type" : "application/json"});
        console.log('Write Head')
        resp.write(JSON.stringify(data));
        console.log('Write body')
        resp.end();
        console.log('end');
    }
}

预期结果：没有错误并返回 JSON

实际结果：

Listening on port 9000....
undefined
Before send
Before Write
Write Head
Write body
end
After send
events.js:174

      throw er; // Unhandled 'error' event
      ^

Error [ERR_STREAM_WRITE_AFTER_END]: write after end
    at write_ (_http_outgoing.js:572:17)
    at ServerResponse.write (_http_outgoing.js:567:10)
    at Object.exports.sendJSON (E:\JARVIS\API\peak-2.0\httpMsgs.js:60:14)
    at db.executeSql (E:\JARVIS\API\peak-2.0\controllers\staff.js:53:33)
    at Execute.conn.execute [as onResult] (E:\JARVIS\API\peak-2.0\db.js:35:9)
    at process.nextTick (E:\JARVIS\API\peak-2.0\node_modules\mysql2\lib\commands\query.js:76:16)
    at process._tickCallback (internal/process/next_tick.js:61:11)
Emitted 'error' event at:
    at writeAfterEndNT (_http_outgoing.js:634:7)
    at process._tickCallback (internal/process/next_tick.js:63:19)