一文了解文件上传全过程（项目中碰到的难点）开发者社区

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一文了解文件上传全过程（项目中碰到的难点）

Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
content-disposition: form-data; name="field1"
Joe Blow
--AaB03x
content-disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
--AaB03x--

<form action="http://localhost:7787/files" method="POST">
	<input name="file" type="file" id="file">
	<input type="submit" value="提交">
</form>

<form action="http://localhost:7787/files" enctype="multipart/form-data" method="POST">
  <input name="file" type="file" id="file">
  <input type="submit" value="提交">
</form>

<input type="file" id="file">
<button id="submit">上传</button>
<script src="https://cdn.bootcss.com/axios/0.19.2/axios.min.js"></script>
<script>
submit.onclick = () => {
    const file = document.getElementById('file').files[0];
    var form = new FormData();
    form.append('file', file);
  	// type 1
    axios.post('http://localhost:7787/files', form).then(res => {
        console.log(res.data);
  	// type 2
  	fetch('http://localhost:7787/files', {
        method: 'POST',
        body: form
    }).then(res => res.json()).tehn(res => {console.log(res)});
  	// type3
  	var xhr = new XMLHttpRequest();
    xhr.open('POST', 'http://localhost:7787/files', true);
    xhr.onload = function () {
    	console.log(xhr.responseText);
    xhr.send(form);
</script>

const json = { hello: "world" };
const blob = new Blob([JSON.stringify(json, null, 2)], { type: 'application/json' });
const form = new FormData();
form.append('file', blob, '1.json');
axios.post('http://localhost:7787/files', form);

const json = { hello: "world" };
const blob = new Blob([JSON.stringify(json, null, 2)], { type: 'application/json' });
const file = new File([blob], '1.json');
form.append('file', file);
axios.post('http://localhost:7787/files', form)

const bufferArrary = [137,80,78,71,13,10,26,10,0,0,0,13,73,72,68,82,0,0,0,1,0,0,0,1,1,3,0,0,0,37,219,86,202,0,0,0,6,80,76,84,69,0,0,255,128,128,128,76,108,191,213,0,0,0,9,112,72,89,115,0,0,14,196,0,0,14,196,1,149,43,14,27,0,0,0,10,73,68,65,84,8,153,99,96,0,0,0,2,0,1,244,113,100,166,0,0,0,0,73,69,78,68,174,66,96,130];
const array = Uint8Array.from(bufferArrary);
const blob = new Blob([array], {type: 'image/png'});
const form = new FormData();
form.append('file', blob, '1.png');
axios.post('http://localhost:7787/files', form)

const base64 = 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAABlBMVEUAAP+AgIBMbL/VAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAACklEQVQImWNgAAAAAgAB9HFkpgAAAABJRU5ErkJggg==';
const byteCharacters = atob(base64);
const byteNumbers = new Array(byteCharacters.length);
for (let i = 0; i < byteCharacters.length; i++) {
	byteNumbers[i] = byteCharacters.charCodeAt(i);
const array = Uint8Array.from(byteNumbers);
const blob = new Blob([array], {type: 'image/png'});
const form = new FormData();
form.append('file', blob, '1.png');
axios.post('http://localhost:7787/files', form);

// request-error.js
const fs = require('fs');
const path = require('path');
const request = require('request');
const stream = fs.readFileSync(path.join(__dirname, '../1.png'));
request.post({
    url: 'http://localhost:7787/files',
    formData: {
        file: stream,
}, (err, res, body) => {
    console.log(body);
})

POST /files HTTP/1.1
host: localhost:7787
content-type: multipart/form-data; boundary=--------------------------437240798074408070374415
content-length: 305
Connection: close
----------------------------437240798074408070374415
Content-Disposition: form-data; name="file"
Content-Type: application/octet-stream
IHDR.............%.V.....PLTE......Ll.....	pHYs..........+.....
IDAT..c`.......qd.....IEND.B`.
----------------------------437240798074408070374415--

<Buffer 01 02>

key: {
    value:  fs.createReadStream('/dev/urandom'),
    options: {
      filename: 'topsecret.jpg',
      contentType: 'image/jpeg'
}

...
request.post({
    url: 'http://localhost:7787/files',
    formData: {
        file: {
            value: stream,
            options: {
                filename: '1.png'
});

const path = require('path');
const FormData = require('form-data');
const fs = require('fs');
const http = require('http');
const form = new FormData();
form.append('file', fs.readFileSync(path.join(__dirname, '../1.png')), {
    filename: '1.png',
    contentType: 'image/jpeg',
const request = http.request({
    method: 'post',
    host: 'localhost',
    port: '7787',
    path: '/files',
    headers: form.getHeaders()
form.pipe(request);
request.on('response', function(res) {
    console.log(res.statusCode);
});

Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
content-disposition: form-data; name="field1"
Joe Blow
--AaB03x
content-disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
--AaB03x--

const path = require('path');
const fs = require('fs');
const http = require('http');
// 定义一个分隔符，要确保唯一性
const boundaryKey = '-------------------------461591080941622511336662';
const request = http.request({
    method: 'post',
    host: 'localhost',
    port: '7787',
    path: '/files',
    headers: {
        'Content-Type': 'multipart/form-data; boundary=' + boundaryKey, // 在请求头上加上分隔符
        'Connection': 'keep-alive'
// 写入内容头部
request.write(
    `--${boundaryKey}\r\nContent-Disposition: form-data; name="file"; filename="1.png"\r\nContent-Type: image/jpeg\r\n\r\n`
// 写入内容
const fileStream = fs.createReadStream(path.join(__dirname, '../1.png'));
fileStream.pipe(request, { end: false });
fileStream.on('end', function () {
    // 写入尾部
    request.end('\r\n--' + boundaryKey + '--' + '\r\n');
request.on('response', function(res) {
    console.log(res.statusCode);
});

// base64 to buffer
const b64string = /* whatever */;
const buf = Buffer.from(b64string, 'base64');

// stream to buffer
function streamToBuffer(stream) {  
  return new Promise((resolve, reject) => {
    const buffers = [];
    stream.on('error', reject);
    stream.on('data', (data) => buffers.push(data))
    stream.on('end', () => resolve(Buffer.concat(buffers))
}

const koaBody = require('koa-body');
app.use(koaBody({ multipart: true }));

.
├── lib
│   ├── file.js
│   ├── incoming_form.js
│   ├── index.js
│   ├── json_parser.js
│   ├── multipart_parser.js
│   ├── octet_parser.js
│   └── querystring_parser.js

index.js
incoming_form.js
1.json_parser
2.multipart_parser
3.octet_parser
4.querystring_parser

...
MultipartParser.prototype.write = function(buffer) {
	console.log(buffer);
  var self = this,
      i = 0,
      len = buffer.length,
      prevIndex = this.index,
      index = this.index,
      state = this.state,
...

<Buffer 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 34 36 31 35 39 31 30 38 30 39 34 31 36 32 32 35 31 31 33 33 36 36 36 ... >
<Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 00 01 00 00 00 01 01 03 00 00 00 25 db 56 ca 00 00 00 06 50 4c 54 45 00 00 ff 80 80 80 4c 6c bf ... >
<Buffer 0d 0a 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 34 36 31 35 39 31 30 38 30 39 34 31 36 32 32 35 31 31 33 33 36 ... >

const fs = require('fs');
const http = require('http');
const querystring = require('querystring');
const server = http.createServer((req, res) => {
  if (req.url === "/files" && req.method.toLowerCase() === "post") {
    parseFile(req, res)
function parseFile(req, res) {
  req.setEncoding("binary");
  let body = "";
  let fileName = "";
  // 边界字符
  let boundary = req.headers['content-type']
    .split('; ')[1]
    .replace("boundary=", "")
  req.on("data", function(chunk) {
    body += chunk;
  req.on("end", function() {
    // 按照分解符切分
    const list = body.split(boundary);
    let contentType = '';
    let fileName = '';
    for (let i = 0; i < list.length; i++) {
      if (list[i].includes('Content-Disposition')) {
        const data = list[i].split('\r\n');
        for (let j = 0; j < data.length; j++) {
          // 从头部拆分出名字和类型
          if (data[j].includes('Content-Disposition')) {
            const info = data[j].split(':')[1].split(';');
            fileName = info[info.length - 1].split('=')[1].replace(/"/g, '');
            console.log(fileName);
          if (data[j].includes('Content-Type')) {
            contentType = data[j];
            console.log(data[j].split(':')[1]);
    // 去除前面的请求头
    const start = body.toString().indexOf(contentType) + contentType.length + 4; // 有多\r\n\r\n
    const startBinary = body.toString().substring(start);
    const end = startBinary.indexOf("--" + boundary + "--") - 2; // 前面有多\r\n
     // 去除后面的分隔符
    const binary = startBinary.substring(0, end);
    const bufferData = Buffer.from(binary, "binary");
    fs.writeFile(fileName, bufferData, function(err) {
      res.end("sucess");

一文了解文件上传全过程（项目中碰到的难点）

一文了解文件上传全过程（项目中碰到的难点）

前言

前置知识

什么是 multipart/form-data?

文件上传为什么要用 multipart/form-data？

multipart/form-data规范是什么？

请求端

浏览端

File

FormData

Blob

ArrayBuffer

Base64

小结

服务端

Buffer

Request

Form-data

原生 Node

主要分为4个部分

Stream、Base64

小结

接收端

Koa-body

Formidable

原生 Node