如何在NodeJS中保存和检索MongoDB格式的pdf文件

npm install mongodb

const MongoClient = require('mongodb').MongoClient;

const url = 'mongodb://localhost:27017'; // MongoDB连接URL
const dbName = 'mydb'; // 数据库名称

MongoClient.connect(url, function(err, client) {
  if (err) {
    console.error('Failed to connect to MongoDB:', err);
    return;
  }

  console.log('Connected to MongoDB successfully');

  const db = client.db(dbName);

  // 在这里执行保存和检索PDF文件的操作

  client.close();
});

const fs = require('fs');
const { Readable } = require('stream');

// 读取PDF文件
const pdfBuffer = fs.readFileSync('path/to/pdf/file.pdf');

// 创建可读流
const readableStream = new Readable();
readableStream.push(pdfBuffer);
readableStream.push(null);

// 保存PDF文件到MongoDB
const bucket = new mongodb.GridFSBucket(db);
const uploadStream = bucket.openUploadStream('file.pdf');
readableStream.pipe(uploadStream);

uploadStream.on('finish', function() {
  console.log('PDF file saved to MongoDB');
});

// 检索PDF文件
const downloadStream = bucket.openDownloadStreamByName('file.pdf');

// 创建可写流
const writableStream = fs.createWriteStream('path/to/save/file.pdf');

// 将PDF文件写入本地文件系统
downloadStream.pipe(writableStream);

writableStream.on('finish', function() {
  console.log('PDF file retrieved from MongoDB');
});