Nodejs Express下载文件，并保存成原文件

现时需要开发一个Excel下载功能

后台有一个API，负责接收传入的JSON文件，生成带图片的Excel文件在临时目录（生成Excel使用npm exceljs库），并将文件通过Router返回

前台Client调用后台API，读取文件流生成Excel文件下载

API生成Excel文件代码

const getLinePlanExcelJson = (data) => {
    // let workBook;
    //workbook properties
    var workBook = new exceljs.Workbook();
    workBook.creator = 'Esquel LPD Project';
    workBook.lastModifiedBy = 'Esquel LPD Project';
    workBook.created = new Date();
    workBook.modified = new Date();


    return new Promise((resolve, reject) => {
        if (typeof (data.customerCode) === 'undefined' || typeof (data.linePlanProducts) === 'undefined') {
            reject(new Error('{"Error Message":"incorrect format."}'));
        }

        //base var
        let mc_productStyles = data.productStyles;
        let mc_productFabrics = data.productFabrics;
        let mc_productTrims = data.productTrims;

        //---------------------------
        let workSheet_name = "LinePlan";

        // create worksheet
        let workSheet = workBook.addWorksheet(workSheet_name, {
            // properties: {
            //     tabColor: { argb: 'FFC0000' }
            // },
            // pageSetup: {
            //     paperSize: 50,
            //     orientation: 'landscape'
            // }
        });


        //setting header title
        let headerTitleArray = config.LinePlan.columns;
        let headerColumns = [];
        for (let headerIndex = 0; headerIndex < headerTitleArray.length; headerIndex++) {
            headerColumns.push({
                header: headerTitleArray[headerIndex].title,
                key: 'col' + headerIndex,
                 headerTitleArray[headerIndex].width
            });
        }
        //setting header to worksheet
        workSheet.columns = headerColumns;

        //setting auto filter
        workSheet.autoFilter = {
            from: 'A1',
            to: 'AA1'
        }
        //----------------------------------------------------

        //col index
        let colIndex = 1;
        let rowIndex = 1;

        data.linePlanProducts.map((linePlanProduct) => {

            //get style data
            let find_StyleData = _.where(mc_productStyles, { styleID: linePlanProduct.productID });

            linePlanProduct.productMaterialConfigs.map((colorway) => {
                //reset col index
                colIndex = 1;
                let newrow = [];

                //style id---------------------------------------
                newrow[colIndex] = linePlanProduct.productID;

                //style image---------------------------------------
                colIndex++;
                newrow[colIndex] = find_StyleData[0].imageURL ? find_StyleData[0].imageURL : '';
                // cell = { v: find_StyleData[0].imageURL, t: 's', l: { Target: find_StyleData[0].imageURL, Tooltip: linePlanProduct.productID } };

                // //colorway body fabirc image---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.PrimaryFabricImageUrl ? colorway.PrimaryFabricImageUrl : '';
                // cell = { v: colorway.PrimaryFabricImageUrl, t: 's', l: { Target: colorway.PrimaryFabricImageUrl, Tooltip: colorway.primaryFabricID } };

                //matching---------------------------------------
                colIndex++;

                //colorway body fabirc item code---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.primaryFabricID;

                //colorway body fabirc info---------------------------------------
                let find_FabricData = _.where(mc_productFabrics, { fabricID: colorway.primaryFabricID });
                colIndex++;
                newrow[colIndex] = find_FabricData[0].longDescriptions[1] ? find_FabricData[0].longDescriptions[1] : '';


                // //colorway body fabirc content---------------------------------------
                colIndex++;
                newrow[colIndex] = find_FabricData[0].longDescriptions[2] ? find_FabricData[0].longDescriptions[2] : '';

                // //fabric width---------------------------------------
                colIndex++;
                newrow[colIndex] = find_FabricData[0].longDescriptions[4] ? find_FabricData[0].longDescriptions[4] : '';


                //button colour---------------------------------------
                colIndex++;

                // // let find_trims = _.where(colorway.appliedAuxiliaries, { auxiliaryType: 'T' });
                // // let find_fabrics = _.where(colorway.appliedAuxiliaries, { auxiliaryType: 'F' });

                // //button1 item code---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.appliedAuxiliaries[0] ? colorway.appliedAuxiliaries[0].auxiliaryID : '';

                //button2 item code---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.appliedAuxiliaries[1] ? colorway.appliedAuxiliaries[1].auxiliaryID : '';

                //button3 item code---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.appliedAuxiliaries[2] ? colorway.appliedAuxiliaries[2].auxiliaryID : '';

                //button4 item code---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.appliedAuxiliaries[3] ? colorway.appliedAuxiliaries[3].auxiliaryID : '';


                // //style fit---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.fitName;

                //style collection---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.collectionName ? linePlanProduct.collectionName + ' Collection' : '';

                //style gender---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.gender;

                //fabric---------------------------------------
                colIndex++;
                newrow[colIndex] = find_FabricData[0].longDescriptions[0] ? find_FabricData[0].longDescriptions[0] : '';


                //style collar---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.collarName;

                //style sleeve---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.sleeveName;


                //style cuff---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.cuffName;

                //style washing---------------------------------------
                colIndex++;

                //style pocket---------------------------------------
                colIndex++;
                newrow[colIndex] = linePlanProduct.pocketName;

                //colorway body pattern pocket---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.bodyPattern;

                //colorway body color name---------------------------------------
                colIndex++;

                //colorway name---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.colorway;

                //colorway plu---------------------------------------
                colIndex++;
                newrow[colIndex] = colorway.pluNumber

                //colorway market---------------------------------------
                let marketArray = [];
                colorway.markets.map((market) => {
                    marketArray.push(market.marketCode);
                });
                colIndex++;
                newrow[colIndex] = marketArray ? marketArray.join('/') : '';


                workSheet.addRow(newrow).commit();

                //setting row style
                // let row = workSheet.lastRow;
                // row.height = 120;

                rowIndex++;
            });
        });


        //need retry array
        let all_needProcessCellArray = [];
        let firsttime_faild_cellArray = [];
        let secendtime_faild_cellArray = [];

        //define add image function
        let fetchImageFun = function (workSheet, cell, CellArray) {
            return new Promise((resolve, reject) => {
                if (!cell.value) resolve('no');

                // let starttime = new Date();
                request.get({ url: cell.value, encoding: null, timeout: 10000 }, function (error, response, body) {
                    if (error) {
                        // let endtime = new Date();
                        // console.log(cell.address + '    Faild ' + starttime + '    ' + endtime);

                        if (CellArray) CellArray.push(cell);
                        resolve('err');
                    }

                    if (body) {
                        if (response.statusCode === 500) {
                            console.log('load image error from url:' + cell.value);
                        } else if (response.statusCode === 404) {
                            console.log('can not load image from url:' + cell.value);
                        }
                        //get image
                        let imageObject = workBook.addImage({
                            buffer: new Buffer(body),
                            extension: response.headers["content-type"]
                        });

                        //add image to cell
                        let imageCellName = cell.address + ':' + cell.address;
                        workSheet.addImage(imageObject, imageCellName);

                        //clear value
                        cell.value = '';

                        resolve('ok');
                    }
                });
            });
        }


        let functionArray = [];
        //add image to cell
        workSheet.eachRow({ includeEmpty: true }, function (row, rowNumber) {
            if (rowNumber > 1) {
                row.height = 150;

                row.eachCell({ includeEmpty: true }, function (cell, colNumber) {

                    cell.alignment = { vertical: 'top', horizontal: 'left' };

                    // cell.border = {
                    //     top: { style: 'thin', color: { argb: 'FFFFFF00' } },
                    //     left: { style: 'thin', color: { argb: 'FFFFFF00' } },
                    //     bottom: { style: 'thin', color: { argb: 'FFFFFF00' } },
                    //     right: { style: 'thin', color: { argb: 'FFFFFF00' } }
                    // };

                    //add image is work
                    if (colNumber === 2 || colNumber === 3) {
                        all_needProcessCellArray.push(cell);
                    }
                });
            }
        });


        all_needProcessCellArray.forEach((getCell) => {
            functionArray.push(fetchImageFun(workSheet, getCell, firsttime_faild_cellArray));
        });
        //add function to array

        //resolve function
        Promise.all(functionArray)
            .then((result) => {

                if (firsttime_faild_cellArray) {
                    firsttime_faild_cellArray.forEach((getCell) => {
                        functionArray.push(fetchImageFun(workSheet, getCell, secendtime_faild_cellArray));
                    });
                    //first time retry
                    Promise.all(functionArray)
                        .then((result2) => {

                            if (secendtime_faild_cellArray) {
                                secendtime_faild_cellArray.forEach((getCell) => {
                                    functionArray.push(fetchImageFun(workSheet, getCell));
                                });
                                //secend time retry
                                Promise.all(functionArray)
                                    .then((result2) => {
                                        resolve(workBook);
                                    }).catch((err3) => {
                                        reject(null);
                                    });
                            } else {
                                resolve(workBook);
                            }

                        }).catch((err2) => {
                            reject(null);
                        });
                } else {
                    resolve(workBook);
                }

            }).catch((err) => {
                reject(null);
            })
    });
}

API路由代码

let express = require('express');
let genCSV = require("./genCSV.js");
let exceljs = require('exceljs');
let util = require('util');
let fs = require('fs');

let router = express.Router();

//post data to router
router.post('/', function (req, res, next) {
  genCSV.getLinePlanExcelJson(req.body)
    .then((excelObject) => {


      // throw new Error('this is test error');

      //return to client
      let fileName = 'LinePlan-' + req.body.linePlanID + '.xlsx';
      let filePath = './public/temp/' + fileName;
      if (fs.existsSync(filePath)) {
        fs.unlink(filePath);
      }

      excelObject.xlsx.writeFile(filePath, { bookType: 'xlsx', bookSST: false, type: 'buffer' })
        .then(() => {
          res.status(200).download(filePath, fileName);
        }).catch((err) => {
          throw err
        });

    })
    .catch((err) => {
      res.status(500).end('{"err":"' + err.message + '"}');
    });
});

module.exports = router;

前台Client调用代码

    fetchMethodExcel: function (apiName, method, requestObject, requestBody, callback) {
      fetch3(this.apiExport(apiName, requestObject), {
        // method: method,
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(requestBody),
      })
        .then((data) => {
          if (data.status === 500) {
            throw new Error('Explort LinePlan API Error');
          } else if (data.status === 404) {
            throw new Error('Can Not Found Explort LinePlan API');
          }
          return data.blob();
        })
        .then((blob) => {
          let a = document.createElement('a');
          let url = window.URL.createObjectURL(blob);

          let filename = 'LinePlan-' + requestBody.linePlanID + '.xlsx';
          a.href = url;
          a.download = filename;
          a.click();
          window.URL.revokeObjectURL(url);

          callback();
        })
        .catch(err => {
          callback(err);
        });
    }

运行结果是

但是下载的文件却是无法打开的，一直说是文件有内容有问题，尝试恢复很久都没有返回。

解除锁定后，可以正常打开文件了