使用Koa2实现服务端的文件上传下载

js
const Koa = require("koa")
const router = require("koa-router")();
const cors = require("koa2-cors")
const fs = require('fs');
const path = require('path');
const {koaBody} = require('koa-body');
console.log(koaBody);
const {saveFile,getFileStream,readFile} = require("./utils/file")

const app = new Koa()


/** 文件上传 */
router.post("/upload",function(ctx,next){
  const file = ctx.request.files.file;
  const uniqueFilename = saveFile(file);
  ctx.body = { filename: uniqueFileName };
})

/** 文件下载 */
router.get("/download/:filename",async function(ctx,next){

  const filename = ctx.params.filename;
  //request里面切出标识符字符串
  let requestUrl = ctx.request.originalUrl;
  //获取资源文件的绝对路径
  let filePath = path.resolve(__dirname + "/uploads/" + decodeURI(filename));
  let resHred = readFile(ctx.headers.range, filePath);
  ctx.status = resHred.code
  ctx.set(resHred.head);
  ctx.set('Content-Disposition', `attachment; filename=${encodeURIComponent(filename)}`);
  ctx.set('Content-Type', 'application/octet-stream');
  let stream = fs.createReadStream(filePath, resHred.code == 200 ? {} : { start: resHred.start, end: resHred.end });
  stream.pipe(ctx.res);
  // //也可使用这种方式。
  // stream.on('data', e => ctx.res.write(e));
  // // 接收完毕
  // stream.on('end', e => ctx.res.end());
  ctx.respond = false;
  return
})
router.post("/index",function(ctx,next){
    ctx.body = {
        data:"token....",
        message:"获取token成功"
    }
})
// app.use(async (ctx) => {
//     ctx.body = "token....."
// })
// app.use(
//     cors({
//         origin: function(ctx){
//             return "*"  //解决跨域
//         },
//         maxAge:5,
//         credentials:true,//是否携带cookie
//         allowMethods:["GET","POST","PUT","DELETE"]
//     })
// )

// koa-body 中间件来解析包含文件的 multipart/form-data 表单数据
app.use(koaBody({ multipart: true }));
app.use(router.routes())
//app.use(router.allowedMethods())
app.listen(3000)

关于文件操作的工具函数file.js

js
const fs = require('fs');
const path = require('path');

function saveFile(file) {
    const reader = fs.createReadStream(file.path);
    const fileExtension = path.extname(file.name);
    const uniqueFileName = `${Date.now()}${fileExtension}`;
    const writer = fs.createWriteStream(path.join(__dirname, 'uploads', uniqueFileName));
    reader.pipe(writer);
    return uniqueFileName;
}

function getFileStream(filename) {
    return fs.createReadStream(path.join(__dirname, '../uploads', filename));
}



  /**
 * [读文件]
 * @param  {String} range        [数据起始位]
 * @param  {String} filePath     [文件路径]
 * @param  {Number} chunkSize    [每次请求碎片大小 （900kb 左右）]
 */
function readFile(range, filePath, chunkSize = 499999 * 2) {
    //mime类型
    const mime = {
        "css": "text/css",
        "gif": "image/gif",
        "html": "text/html",
        "ico": "image/x-icon",
        "jpeg": "image/jpeg",
        "jpg": "image/jpeg",
        "js": "text/javascript",
        "json": "application/json",
        "pdf": "application/pdf",
        "png": "image/png",
        "svg": "image/svg+xml",
        "swf": "application/x-shockwave-flash",
        "tiff": "image/tiff",
        "txt": "text/plain",
        "mp3": "audio/mp3",
        "wav": "audio/x-wav",
        "wma": "audio/x-ms-wma",
        "wmv": "video/x-ms-wmv",
        "xml": "text/xml",
        "mp4": "video/mp4"
    };
    // 获取后缀名
    let ext = path.extname(filePath);
    ext = ext ? ext.slice(1) : 'unknown';
    //未知的类型一律用"text/plain"类型
    let contentType = mime[ext.toLowerCase()];
 
    //建立流对象，读文件
    let stat = fs.statSync(filePath)
    let fileSize = stat.size;
    let head = {
        code: 200,
        head: {
            'Content-Length': fileSize,
            'content-type': contentType,
        }
 
    };
    console.log("range: ",range);
    if (range) {
        // 大文件分片
        let parts = range.replace(/bytes=/, "").split("-");
        let start = parseInt(parts[0], 10);
        let end = parts[1] ? parseInt(parts[1], 10) : start + chunkSize;
        end = end > fileSize - 1 ? fileSize - 1 : end;
        chunkSize = (end - start) + 1;
        head = {
            code: 206,
            filePath,
            start,
            end,
            head: {
                'Content-Range': `bytes ${start}-${end}/${fileSize}`,
                'content-type': contentType,
                'Content-Length': chunkSize,
                'Accept-Ranges': 'bytes'
            }
        }
 
    }
    return head;
}


module.exports = {
    saveFile,
    getFileStream,
    readFile
}