如何使用Koa上传文件？

Question

我正在搭建一个新服务器，想要支持高级上传功能。首先，我需要验证文件（文件类型、文件大小、最大计数），最后将其上传到某个目的地。我用 koa-multer 尝试了一些东西，但我无法得到 multer 验证错误。

multer.js

const multer = require('koa-multer')

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, './public/uploads/')
  },
  filename: function (req, file, cb) {
    var fileFormat = (file.originalname).split('.')
    cb(null, file.fieldname + '_' + Date.now() + '.' + fileFormat[fileFormat.length - 1])
  }
})

const fileFilter = (req, file, cb) => {
  if (file.mimetype === 'image/jpeg' || file.mimetype === 'image/png') {
    cb(null, true)
  } else {
    cb(new Error('This is not image file type'), false)
  }
}

const upload = multer({
  storage: storage,
  limits: {
    fileSize: 1024 * 1024 * 1,
    files: 5
  },
  fileFilter: fileFilter
})

module.exports = upload

router.js

const Router = require('koa-router')

const multer = require('../middlewares/multer')
const auth = require('../middlewares/auth')
const controller = require('../controllers').userController

const schemas = require('../schemas/joi_schemas')
const validation = require('../middlewares/validation')

const router = new Router()

const BASE_URL = `/users`

router.post(BASE_URL, auth , validation(schemas.uPOST, 'body'), controller.

addUser)
    router.put(`${BASE_URL}/:id`, auth , multer.single('logo')(ctx, (err) => {
  if (err) {
    ctx.body = {
      success: false,
      message: 'This is not image file'
    }
  }
}),  controller.editUser)
router.delete(`${BASE_URL}/:id`, auth , controller.deleteUser)

module.exports = router.routes()

如何以最佳方式解决上传问题，以便长期维护代码？

Answer 1

koa 中间件就像一个嵌套的回调，你应该在 multer

之后捕获 "next()" 而不是

router.put(`${BASE_URL}/:id`, auth , async (ctx, next) => {
  try{
    await next()
  } catch(err) {
    ctx.body = {
      success: false,
      message: 'This is not image file'
    }
  }
}, multer.single('logo'),  controller.editUser)

但是你这样做，它也会捕获 controller.editUser 控制器本身没有捕获到的错误。

Answer 2

上传文件最简单的方法如下（假设表单有一个名为 avatar 的文件上传字段：

const Koa = require('koa')
const mime = require('mime-types')
const Router = require('koa-router')
const koaBody = require('koa-body')({multipart: true, uploadDir: '.'})

const router = new Router()

router.post('/register', koaBody, async ctx => {
    try {
        const {path, name, type} = ctx.request.files.avatar
        const fileExtension = mime.extension(type)
        console.log(`path: ${path}`)
        console.log(`filename: ${name}`)
        console.log(`type: ${type}`)
        console.log(`fileExtension: ${fileExtension}`)
        await fs.copy(path, `public/avatars/${name}`)
        ctx.redirect('/')
    } catch(err) {
        console.log(`error ${err.message}`)
        await ctx.render('error', {message: err.message})
    }
})

请注意，此示例使用 Async Functions，它允许使用标准 try-catch 块处理异常的干净代码。

Answer 3

您可以使用以下两个选项之一：

第一种是在路由末尾添加回调函数

const multer = require('@koa/multer')

//Options to limit file size and file extension
const upload = multer({
        dest: '../avatars',
        limits: {
            fileSize: 1024*1024
        },
        fileFilter(ctx, file, cb) {
            if (!file.originalname.match(/\.(jpg|jpeg|png)$/)) {
                return cb(new Error('Please upload a World document'))
            }
            cb(undefined, true)
        }
    })



//The last callback should handle the error from multer
router
        .post('/upload', upload.single('upload'), async (ctx) => {
            ctx.status = 200
        }, (error, ctx) => {
            ctx.status = 400
            ctx.body = error.message
        })
})

第二个选项是在调用 multer 中间件之前添加 try/catch:

router
    .post('/upload', async (ctx, next) => {
              try {
            await next()
            ctx.status = 200
        } catch (error) {
            ctx.status = 400
            ctx.body = error.message
        }
    }, upload.single('upload'), async ctx => {ctx.status = 200})

最后一种情况如果multer会抛出异常，会在之前的await next()try/catch中处理try/catch

如何使用Koa上传文件？

How to upload file using Koa?

node.js

koa

koa2