Node.js 从谷歌云存储读取Excel文件

我正在尝试读取一个从应用程序引擎上运行的Nodejs应用程序上传到谷歌存储的电子表格

Nodejs中@google cloud/storage package提供的函数是createReadStream（）。我正在将此流传递给Exceljs对象

代码如下：

const blob = bucket.file(req.file.originalname);
const blobStream = blob.createWriteStream();
blobStream.on('finish', () => {

    let readStream = storage.bucket(bucket.name).file(blob.name).createReadStream();

    let returnString = '';

    const workbook = new Excel.stream.xlsx.WorkbookReader();
        var options = {
        entries: "emit",
        sharedStrings: "cache",
        worksheets: "emit"
    };

    workbook.read(readStream, options);

    workbook.on('worksheet', function (worksheet) {
        console.log("worksheet", worksheet.name);
        worksheet.on('row', function (row) {
            if(row.values.length > 0){
                console.log(" row.values", row.values[1]);
                returnString += row.values[1] + " ";
            }
        });

        worksheet.on('close', function () {
            console.log("worksheet close");
        });

        worksheet.on('finished', function () {
            console.log("worksheet finished");
            res.send(returnString);
        });
    });
});

blobStream.end(req.file.buffer);

workbook.read（readStream，options）是否获得正确的readStream

由于我在提到这一点时遇到以下错误：

UnhandledPromiseRejectionWarning: Error: Could not recognise input
2019-07-07 20:35:09 default[20190708t020308]      at module.exports._getStream (/srv/node_modules/exceljs/dist/es5/stream/xlsx/workbook-reader.js:58:11)
2019-07-07 20:35:09 default[20190708t020308]      at module.exports.read (/srv/node_modules/exceljs/dist/es5/stream/xlsx/workbook-reader.js:79:37)
2019-07-07 20:35:09 default[20190708t020308]      at Pumpify.blobStream.on (/srv/app.js:80:14)
2019-07-07 20:35:09 default[20190708t020308]      at Pumpify.emit (events.js:198:13)
2019-07-07 20:35:09 default[20190708t020308]      at finishMaybe (/srv/node_modules/readable-stream/lib/_stream_writable.js:630:14)
2019-07-07 20:35:09 default[20190708t020308]      at afterWrite (/srv/node_modules/readable-stream/lib/_stream_writable.js:492:3)
2019-07-07 20:35:09 default[20190708t020308]      at onwrite (/srv/node_modules/readable-stream/lib/_stream_writable.js:483:7)
2019-07-07 20:35:09 default[20190708t020308]      at Pumpify.WritableState.onwrite (/srv/node_modules/readable-stream/lib/_stream_writable.js:180:5)
2019-07-07 20:35:09 default[20190708t020308]      at Object.onceWrapper (events.js:286:20)
2019-07-07 20:35:09 default[20190708t020308]      at Pumpify.emit (events.js:198:13)
2019-07-07 20:35:09 default[20190708t020308]      at Pumpify.Duplexify.uncork (/srv/node_modules/duplexify/index.js:77:50)

---

当您使用multer和云存储上传文件时，“过程”是： 您在multer的缓冲区中有一个文件，然后，使用此缓冲区，您在云存储中写入一个文件，因此您可以利用这一点，只需使用exceljs读取multer缓冲区

const Stream = require('stream'); //Stream is a node resourse
const blob = bucket.file(req.file.originalname);
const blobStream = blob.createWriteStream();
blobStream.on('finish', () => {
  // ToDo when the file has uploaded in storage
})
let workbook = new Excel.Workbook();
let stream = new Stream.Readable(); 
stream.push(req.file.buffer); // using multer buffer
stream.push(null);
workbook.xlsx.read(stream).then((workbook)=> {
  // ToDo with excel file readed
})

---

在这里查看exceljs代码的源代码。。。您的流似乎不是“stream.Readable”的实例。这将是我的第一次测试。。。确保您的readStream在使用时感觉良好。之前我将文件上载到云存储，然后从云函数读取，但现在我直接从缓冲区读取。