尝试使用 Node.js 下载 PDF 文件时出现“无文件”或空文件

Question

The issue:

I need to download a PDF file from my server but getting either "No file" or empty file

Details:

Here is my server-side code:

let fileBuffered = '';

// authentication for downloading a file from Dropbox API to my server
    const dropbox = dropboxV2Api.authenticate({
        token: process.env.DEV_DROPBOX_SECRET_KEY
    });

    // configuring parameters
    const params = Object.freeze({
        resource: "files/download",
        parameters: {
            path: `/${customerFileFolder}/${fileName}`
        }
    });

    let dropboxPromise = new Promise(function (resolve, reject) {
        dropbox(params, function (err, result) {
            if (err) {
                reject(err);
            } else {
                resolve(result);
            }
        }).on('data',function(data) {
                fileBuffered += data;
        })
    const file = fileBuffered;

    res.setHeader("Content-Type", "application/octet-stream");
    res.send(file);

The PDF file's that I'm trying to download size is 139,694 bytes. The length of the fileBuffered variable is 132,597. Here is the content of the variable as it is shown in the debugger: Seems like a legit PDF file

Here is the client-side

function documentFileDownload(fileName) {
    const ip = location.host;
    let request = $.ajax({
        type: "POST",
        url: `${http() + ip}/documentFileDownload`,

        headers: {
            "Accept": "application/octet-stream"
        },


        data: {
            fileName: fileName
        },
        error: function (err) {
            console.log("ERROR: " + err);
        }
    });

    console.log(request);

    return request;
}

Problem: Then I get the response on a client-side it looks like this:

Note the size of the responseText: 254Kb. What I actually get in the browser is a "Failed - No file" message

What else I tried:

I tried to play with different Content-Types (application/pdf, text/pdf) on a server-side and tried to convert the variable to base64 buffer

const file = `data:application/pdf;base64, ${Buffer.from(fileBuffered).toString("base64")}`;

and added res.setHeader("Accept-Encoding", "base64"); but still getting the same result.

Any ideas?

Answer 1

I found a solution. I missed a .on("end", ) event while reading data from Dropbox stream. Here is a working solution:

Here is the server-side:

let chunk = [];
let fileBuffered = '';

// authentication for downloading a file from Dropbox API to my server
    const dropbox = dropboxV2Api.authenticate({
        token: process.env.DEV_DROPBOX_SECRET_KEY
    });

    // configuring parameters
    const params = Object.freeze({
        resource: "files/download",
        parameters: {
            path: `/${customerFileFolder}/${fileName}`
        }
    });

    let dropboxPromise = new Promise(function (resolve, reject) {
        dropbox(params, function (err, result) {
            if (err) {
                reject(err);
            } else {
                resolve(result);
            }
        }).on('data',function(data) {
                fileBuffered += data;
        }).on('end', () => {
                // console.log("finish");\
                // generate buffer
                fileBuffered = Buffer.concat(chunk);
            });

    const file = `data:application/pdf;base64, ${Buffer.from(fileBuffered).toString("base64")}`;
    res.setHeader("Content-Type", "application/pdf");
    res.send(file);

Client-side:

function documentFileDownload(fileName) {
    const ip = location.host;
    let request = $.ajax({
        type: "POST",
        url: `${http() + ip}/documentFileDownload`,
        responseType: "arraybuffer",
        headers: {
            "Accept": "application/pdf"
        },

        data: {
            fileName: fileName
        },
        error: function (err) {
            console.log("ERROR: " + err);
        }
    });

    // console.log(request);
    return request;
}

Answer 2

Try adding dataType: "blob" in your $.ajax method

and within the headers object add this 'Content-Type', 'application/json' .