[英]Generate pdf file using pdfkit and send it to browser in nodejs-expressjs
[英]ExpressJS and PDFKit - generate a PDF in memory and send to client for download
In my api
router, there is a function called generatePDF
which aims to use PDFKit module to generate a PDF file in memory and send to client for download instead of displaying only.
在api.js
:
var express = require('express');
var router = express.Router();
const PDFDocument = require('pdfkit');
router.get('/generatePDF', async function(req, res, next) {
var myDoc = new PDFDocument({bufferPages: true});
myDoc.pipe(res);
myDoc.font('Times-Roman')
.fontSize(12)
.text(`this is a test text`);
myDoc.end();
res.writeHead(200, {
'Content-Type': 'application/pdf',
'Content-disposition': 'attachment;filename=test.pdf',
'Content-Length': 1111
});
res.send( myDoc.toString('base64'));
});
module.exports = router;
這不起作用。 錯誤消息是(node:11444) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
。
我該如何解決問題並使其正常工作?
另外,一個相關的問題是如何將 PDF 生成的業務邏輯與路由器分離並將它們鏈接起來?
完整的解決方案。
var express = require('express');
var router = express.Router();
const PDFDocument = require('pdfkit');
router.get('/generatePDF', async function(req, res, next) {
var myDoc = new PDFDocument({bufferPages: true});
let buffers = [];
myDoc.on('data', buffers.push.bind(buffers));
myDoc.on('end', () => {
let pdfData = Buffer.concat(buffers);
res.writeHead(200, {
'Content-Length': Buffer.byteLength(pdfData),
'Content-Type': 'application/pdf',
'Content-disposition': 'attachment;filename=test.pdf',})
.end(pdfData);
});
myDoc.font('Times-Roman')
.fontSize(12)
.text(`this is a test text`);
myDoc.end();
});
module.exports = router;
首先,我建議為 PDF 套件創建服務。 然后是 Controller 到您想要的路線。
我使用get-stream
使這更容易。
它還回答了您對已接受答案的問題:
如何將 PDF 一代的業務邏輯與路由器分離並將它們鏈接起來?
這是我的專業解決方案:
import PDFDocument from 'pdfkit';
import getStream from 'get-stream';
import fs from 'fs';
export default class PdfKitService {
/**
* Generate a PDF of the letter
*
* @returns {Buffer}
*/
async generatePdf() {
try {
const doc = new PDFDocument();
doc.fontSize(25).text('Some text with an embedded font!', 100, 100);
if (process.env.NODE_ENV === 'development') {
doc.pipe(fs.createWriteStream(`${__dirname}/../file.pdf`));
}
doc.end();
const pdfStream = await getStream.buffer(doc);
return pdfStream;
} catch (error) {
return null;
}
}
}
然后是Controller的方法:
(...)
async show(req, res) {
const pdfKitService = new PdfKitService();
const pdfStream = await pdfKitService.generatePdf();
res
.writeHead(200, {
'Content-Length': Buffer.byteLength(pdfStream),
'Content-Type': 'application/pdf',
'Content-disposition': 'attachment;filename=test.pdf',
})
.end(pdfStream);
}
最后是路線:
routes.get('/pdf', FileController.show);
對於那些不想浪費內存來緩沖 PDF 並立即將塊發送給客戶端的人:
const filename = `Receipt_${invoice.number}.pdf`;
const doc = new PDFDocument({ bufferPages: true });
const stream = res.writeHead(200, {
'Content-Type': 'application/pdf',
'Content-disposition': `attachment;filename=${filename}.pdf`,
});
doc.on('data', (chunk) => stream.write(chunk));
doc.on('end', () => stream.end());
doc.font('Times-Roman')
.fontSize(12)
.text(`this is a test text`);
doc.end();
您可以像這樣使用blob stream。
參考: https://pdfkit.org/index.html
const PDFDocument = require('pdfkit');
const blobStream = require('blob-stream');
// create a document the same way as above
const doc = new PDFDocument;
// pipe the document to a blob
const stream = doc.pipe(blobStream());
// add your content to the document here, as usual
doc.font('fonts/PalatinoBold.ttf')
.fontSize(25)
.text('Some text with an embedded font!', 100, 100);
// get a blob when you're done
doc.end();
stream.on('finish', function() {
// get a blob you can do whatever you like with
const blob = stream.toBlob('application/pdf');
// or get a blob URL for display in the browser
const url = stream.toBlobURL('application/pdf');
iframe.src = url;
});
pipe 所有 pdf 數據到您的 blob,然后將其寫入文件或 url。 或者您可以將 pdf 直接存儲到雲存儲中,如 firebase 存儲並將下載鏈接發送給客戶端。
如果您想動態生成 pdf,那么您還可以在節點中嘗試 html-pdf 庫,它允許您從 html 模板創建 pdf 並在其中添加動態數據。 它也比 pdfkit https://www.npmjs.com/package/html-pdf更可靠 另請參閱此鏈接Generate pdf file using pdfkit and send it to browser in nodejs-expressjs
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