How to transfer files in nodejs and store them in the database at the same time

Node.js is a very powerful back-end development language, which can easily transfer files to the server. At the same time, it can also persist these files to the database. This article will briefly introduce how to simultaneously transfer files and persist files to the database through Node.js.

Transfer files to server

In Node.js, you can use the Express framework to receive files and upload them to the server. To upload files you need to use a library called Multer. Multer is a middleware for processing multipart/form-data data in Node.js. It is built on busboy and can use Node.js's built-in multipart module to handle file uploads.

To use Multer, you first need to install it. Multer can be installed from the command line using the following command:

npm install --save multer

Once installed, you can import the middleware from Multer and add it to your Express application:

const express = require('express');
const multer = require('multer');
const app = express();
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.single('file'), (req, res) => {
  // 处理文件上传
  res.send('文件已上传');
});

in the above In the code, the upload.single method stores the uploaded file in the specified directory. In this case, the files will be stored in a folder named "Uploads".

Uploading files from the client

It is now possible to upload files to the server in Node.js. But how to upload files from client to server? HTML5 provides an input type called , which can be used to upload files to the server. In HTML, you can add a form for uploading files to the client using the following code:

<form action="/upload" enctype="multipart/form-data" method="POST">
  <input type="file" name="file">
  <input type="submit" value="上传文件">
</form>

In the above HTML code, after submitting the form, the file will be uploaded to the route named "/upload".

Storing files to the database

After uploading the file to the server, it needs to be saved in the database. Here are some ways to save files to common database systems:

Saving files into MongoDB

To store files in MongoDB, you can convert the files to binary data and about Additional details of the file (such as file name and file type) are then stored in MongoDB GridFS.

The following is an example to store a file in MongoDB:

const MongoClient = require('mongodb').MongoClient;
const Grid = require('gridfs-stream');

MongoClient.connect('mongodb://localhost/my_database', (err, client) => {
  const db = client.db('my_database');
  const gfs = Grid(db, require('mongodb'));
  
  const writestream = gfs.createWriteStream({
      filename: 'my_file.txt'
  });
  
  fs.createReadStream('./uploads/my_file.txt').pipe(writestream);
});

In the above code, the gridfs-stream library is used to save the file to a directory called "my_file .txt" document. This library allows storing large binary data (such as files) in MongoDB using MongoDB GridFS.

Saving a file into MySQL

To store a file in MySQL, you can do this by creating a BLOB row that contains the file's binary data. Here is an example of storing a file into a MySQL database:

const mysql = require('mysql');

const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: '',
  database: 'my_database'
});

const file = fs.readFileSync('./uploads/my_file.txt');
const sql = 'INSERT INTO files (filename, file) VALUES (?, ?)';
const values = ['my_file.txt', file];
connection.query(sql, values, (error, results, fields) => {
  if (error) throw error;
  res.send('文件已上传');
});

In the above code, the file is read into memory and then inserted into a file named "files" using MySQL's query method table.

Conclusion

This article describes how to use Node.js to upload files from the client to the server and store the files in the database. By using Multer middleware, files can be easily uploaded to the server. To store files in MongoDB or MySQL, you can use GridFS and BLOB data types respectively to save the files in the corresponding database. This is a very powerful feature that is used in many web applications.

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