从REST API返回的图像始终显示为损坏 [英] Image returned from REST API always displays broken
问题描述
我正在使用React构建用于艺术品投资组合应用程序的内容管理系统.客户端将发布到使用Mongoose插入到MongoDB中的API.然后,API向数据库查询新插入的图像,并将其返回给客户端.
I am building a content management system for an art portfolio app, with React. The client will POST to the API which uses Mongoose to insert into a MongoDB. The API then queries the DB for the newly inserted image, and returns it to the client.
这是我的使用Mongoose连接到MongoDB的代码:
Here's my code to connect to MongoDB using Mongoose:
mongoose.connect('mongodb://localhost/test').then(() =>
console.log('connected to db')).catch(err => console.log(err))
mongoose.Promise = global.Promise
const db = mongoose.connection
db.on('error', console.error.bind(console, 'MongoDB connection error:'))
const Schema = mongoose.Schema;
const ImgSchema = new Schema({
img: { data: Buffer, contentType: String }
})
const Img = mongoose.model('Img', ImgSchema)
我正在使用multer和fs处理图像文件.我的POST端点看起来像这样:
I am using multer and fs to handle the image file. My POST endpoint looks like this:
router.post('/', upload.single('image'), (req, res) => {
if (!req.file) {
res.send('no file')
} else {
const imgItem = new Img()
imgItem.img.data = fs.readFileSync(req.file.path)
imgItem.contentType = 'image/png'
imgItem
.save()
.then(data =>
Img.findById(data, (err, findImg) => {
console.log(findImg.img)
fs.writeFileSync('api/uploads/image.png', findImg.img.data)
res.sendFile(__dirname + '/uploads/image.png')
}))
}
})
我可以在文件结构中看到writeFileSync正在将映像写入磁盘. res.sendFile抓取它并将其发送给客户端.
I can see in the file structure that writeFileSync is writing the image to the disk. res.sendFile grabs it and sends it down to the client.
客户端代码如下:
handleSubmit = e => {
e.preventDefault()
const img = new FormData()
img.append('image', this.state.file, this.state.file.name)
axios
.post('http://localhost:8000/api/gallery', img, {
onUploadProgress: progressEvent => {
console.log(progressEvent.loaded / progressEvent.total)
}
})
.then(res => {
console.log('responsed')
console.log(res)
const returnedFile = new File([res.data], 'image.png', { type: 'image/png' })
const reader = new FileReader()
reader.onloadend = () => {
this.setState({ returnedFile, returned: reader.result })
}
reader.readAsDataURL(returnedFile)
})
.catch(err => console.log(err))
}
这确实将返回的文件和img数据url都置于了状态.但是,在我的应用程序中,图像始终显示为损坏.
This does successfully place both the returned file and the img data url on state. However, in my application, the image always displays broken.
以下是一些屏幕截图:
该如何解决?
推荐答案
避免发送回base64编码的图像(多个图像+大文件+大编码字符串=非常慢的性能).我强烈建议创建一个微服务,该微服务仅处理图像上载以及任何其他与图像相关的获取/发布/放置/删除请求.将其与主应用程序分开.
Avoid sending back base64 encoded images (multiple images + large files + large encoded strings = very slow performance). I'd highly recommend creating a microservice that only handles image uploads and any other image related get/post/put/delete requests. Separate it from your main application.
例如:
- 我使用multer创建图像缓冲区
- 然后使用Sharp或fs保存图像(取决于文件类型)
- 然后我将文件路径发送到控制器以保存到数据库中
- 然后,前端在尝试访问时发出GET请求:
http://localhost:4000/uploads/timestamp-randomstring-originalname.fileext
- I use multer to create an image buffer
- Then use sharp or fs to save the image (depending upon file type)
- Then I send the filepath to my controller to be saved to my DB
- Then, the front-end does a GET request when it tries to access:
http://localhost:4000/uploads/timestamp-randomstring-originalname.fileext
简单来说,我的微服务就像CDN一样,仅用于图像.
例如,用户使用某些FormData向http://localhost:4000/api/avatar/create
发送发布请求:
For example, a user sends a post request to http://localhost:4000/api/avatar/create
with some FormData:
它首先通过一些Express中间件:
It first passes through some Express middlewares:
libs/middlewares.js
...
app.use(cors({credentials: true, origin: "http://localhost:3000" })) // allows receiving of cookies from front-end
app.use(morgan(`tiny`)); // logging framework
app.use(multer({
limits: {
fileSize: 10240000,
files: 1,
fields: 1
},
fileFilter: (req, file, next) => {
if (!/\.(jpe?g|png|gif|bmp)$/i.test(file.originalname)) {
req.err = `That file extension is not accepted!`
next(null, false)
}
next(null, true);
}
}).single(`file`))
app.use(bodyParser.json()); // parses header requests (req.body)
app.use(bodyParser.urlencoded({ limit: `10mb`, extended: true })); // allows objects and arrays to be URL-encoded
...etc
然后点击avatars
路线:
routes/avatars.js
app.post(`/api/avatar/create`, requireAuth, saveImage, create);
然后通过一些用户身份验证,然后通过我的saveImage
中间件:
It then passes through some user authentication, then goes through my saveImage
middleware:
services/saveImage.js
const createRandomString = require('../shared/helpers');
const fs = require("fs");
const sharp = require("sharp");
const randomString = createRandomString();
if (req.err || !req.file) {
return res.status(500).json({ err: req.err || `Unable to locate the requested file to be saved` })
next();
}
const filename = `${Date.now()}-${randomString}-${req.file.originalname}`;
const filepath = `uploads/${filename}`;
const setFilePath = () => { req.file.path = filepath; return next();}
(/\.(gif|bmp)$/i.test(req.file.originalname))
? fs.writeFile(filepath, req.file.buffer, (err) => {
if (err) {
return res.status(500).json({ err: `There was a problem saving the image.`});
next();
}
setFilePath();
})
: sharp(req.file.buffer).resize(256, 256).max().withoutEnlargement().toFile(filepath).then(() => setFilePath())
如果文件被保存,它将发送req.file.path
到我的create
控制器.这将作为文件路径和图像路径保存到我的数据库中(保存avatarFilePath
或/uploads/imagefile.ext
用于删除目的,保存avatarURL
或[http://localhost:4000]/uploads/imagefile.ext
并将其用于前端GET请求) :
If the file is saved, it then sends a req.file.path
to my create
controller. This gets saved to my DB as a file path and as an image path (the avatarFilePath
or /uploads/imagefile.ext
is saved for removal purposes and the avatarURL
or [http://localhost:4000]/uploads/imagefile.ext
is saved and used for the front-end GET request):
controllers/avatars.js (我使用的是Postgres,但您可以替代Mongo)
controllers/avatars.js (I'm using Postgres, but you can substitute for Mongo)
create: async (req, res, done) => {
try {
const avatarurl = `${apiURL}/${req.file.path}`;
await db.result("INSERT INTO avatars(userid, avatarURL, avatarFilePath) VALUES ($1, $2, $3)", [req.session.id, avatarurl, req.file.path]);
res.status(201).json({ avatarurl });
} catch (err) { return res.status(500).json({ err: err.toString() }); done();
}
然后,当前端尝试通过<img src={avatarURL} alt="image" />
或<img src="[http://localhost:4000]/uploads/imagefile.ext" alt="image" />
访问uploads
文件夹时,它将由微服务提供服务:
Then when the front-end tries to access the uploads
folder via <img src={avatarURL} alt="image" />
or <img src="[http://localhost:4000]/uploads/imagefile.ext" alt="image" />
, it gets served up by the microservice:
库/server.js
const express = require("express");
const path = app.get("path");
const PORT = 4000;
//============================================================//
// EXPRESS SERVE AVATAR IMAGES
//============================================================//
app.use(`/uploads`, express.static(`uploads`));
//============================================================//
/* CREATE EXPRESS SERVER */
//============================================================//
app.listen(PORT);
记录请求时的外观:
19:17:54 INSERT INTO avatars(userid, avatarURL, avatarFilePath) VALUES ('08861626-b6d0-11e8-9047-672b670fe126', 'http://localhost:4000/uploads/1536891474536-k9c7OdimjEWYXbjTIs9J4S3lh2ldrzV8-android.png', 'uploads/1536891474536-k9c7OdimjEWYXbjTIs9J4S3lh2ldrzV8-android.png')
POST /api/avatar/create 201 109 - 61.614 ms
GET /uploads/1536891474536-k9c7OdimjEWYXbjTIs9J4S3lh2ldrzV8-android.png 200 3027 - 3.877 ms
用户在成功执行GET请求后看到的内容:
What the user sees upon successful GET request:
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