I am writing a web server application using Dart.
How do I send an image file through a HttpServer to the browser?
When you receive a request for an image, send a header to state the content type and length, and then the file contents.
import 'dart:io';
void main() {
HttpServer.bind('127.0.0.1', 8080).then((server) {
server.listen((HttpRequest request) {
File image = new File("chicken.jpeg");
image.readAsBytes().then(
(raw){
request.response.headers.set('Content-Type', 'image/jpeg');
request.response.headers.set('Content-Length', raw.length);
request.response.add(raw);
request.response.close();
});
});
});
}
Related
I am using dart:io to create the server. I send the request from the Postman with form-data. I need to use form-data because my old API from another language uses it and the app uses it too.
At the moment. I am trying to get the data and files with this code:
Future main(List<String> arguments) async {
HttpServer server = await HttpServer.bind('localhost', 8085);
server.listen((HttpRequest request) async {
String jsonString = await request.cast<List<int>>().transform(utf8.decoder).join();
print("jsonString:\n$jsonString");
await request.response.close();
});
}
When I send the data and a file from the Postman with this below.
I will get the error below.
Unhandled exception:
FormatException: Unexpected extension byte (at offset 435)
If I don't send the file as image 1, I got this.
jsonString:
----------------------------166099235909119466948633
Content-Disposition: form-data; name="key 1"
Content-Type: application/json
value 1
----------------------------166099235909119466948633
Content-Disposition: form-data; name="key 2"
value 2
----------------------------166099235909119466948633--
I can't convert the above results to variables.
I don't know how to do that. Has anyone an example for doing this or suggest any package to me? This is my first time creating a dart server.
I follow this.
You can get the data and files from the request by using shelf_multipart (Other packages may be used in conjunction with this one and find more methods on GitHub).
If you want to see results quickly that it can be done. Follow this below.
I am using 3 packages including the shelf, shelf_router, and shelf_multipart packages.
You need to add these packages to your pubspec.yaml.
(You can copy and paste these into your pubspec.yaml.)
dependencies:
shelf: ^1.4.0
shelf_router: ^1.1.3
shelf_multipart: ^1.0.0
Then copy my code and past it to your main.dart:
import 'dart:convert';
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as shelf_io;
import 'package:shelf_router/shelf_router.dart';
import 'package:shelf_multipart/form_data.dart';
import 'package:shelf_multipart/multipart.dart';
Future main(List<String> arguments) async {
final service = Service();
final server = await shelf_io.serve(service.handler, 'localhost', 8085);
print('Server running on localhost:${server.port}');
}
class Service {
Handler get handler {
final router = Router();
router.post("/example", (Request request) async {
if (request.isMultipart && request.isMultipartForm) {
Map<String, dynamic>? data = await RequestConverter.formData(request);
return data != null
? Response.ok("form-data: true, receive-data: true, data: $data")
: Response.ok("form-data: true, receive-data: false");
}
return Response.ok("form-data: false");
});
router.all('/<ignored|.*>', (Request request) {
return Response.notFound('Page not found');
});
return router;
}
}
class RequestConverter {
static Future<Map<String, dynamic>?> formData(Request request) async {
try {
Map<String, dynamic> data = {};
Map<String, dynamic> files = {};
final List<FormData> formDataList = await request.multipartFormData.toList();
for (FormData formData in formDataList) {
if (formData.filename == null) {
String dataString = await formData.part.readString();
data[formData.name] = Json.tryDecode(dataString) ?? dataString; //Postman doesn't send data as json
} else if (formData.filename is String) {
files[formData.name] = await formData.part.readBytes();
}
}
return {"data": data, "files": files};
} catch (e) {
return null;
}
}
}
class Json {
static String? tryEncode(data) {
try {
return jsonEncode(data);
} catch (e) {
return null;
}
}
static dynamic tryDecode(data) {
try {
return jsonDecode(data);
} catch (e) {
return null;
}
}
}
After this, you can start your server in your terminal. For me I am using:
dart run .\bin\main.dart
Finally, open the Postman and paste http://localhost:8085/example to the URL field, select the POST method, and form-data. You can add the data into the KEY and VALUE fields. Then press send.
This is my example in the Postman:
This solution work with http.MultipartRequest() from the Flutter app.
I am trying to send file from Client (Angular) to the NestJS same way like it is working now with Java-springboot API.
I am using POST method in NestJS but, unfortunatelly I am not able to got any data from the body :
here is the code :
#Post('/uploadExportFile')
uploadAttachment(#Req() req: Request, #Body() attachment: ArrayBuffer): any {
console.log(attachment);
return {};
}
content-type is set in header on Client side, I am not sure if I need to set content-types there ? Content type depends on file mimetype it should be (application/pdf/png/jpeg)..not multiform or what I need to do to achieve that attachment object will not return empty {} .
req.body is undefined
What I need to do with that file is to again change it back to Base64 (in angular it is in Base64) but Java API consumes only byte[] so I need to keep that like it is on FE.
any suggestions what is wrong in this "simple" code?
** EDIT **
====↓ EDIT ↓====
Solution: request.body is undefined is:
NestJS use as default body jsonBody, so in that case you have to override for specific routes that you want to use raw-body, and if raw-body is used insted of jsonBody, then the body from request is not undefined and it contain ArrayBuffer.
What you need to do is something like this;
Create rawBody middleware raw-body.middleware.ts
import { Injectable, NestMiddleware } from '#nestjs/common';
import { Request, Response } from 'express';
import * as bodyParser from 'body-parser';
#Injectable()
export class RawBodyMiddleware implements NestMiddleware {
use(req: Request, res: Response, next: () => any) {
bodyParser.raw({type: '*/*'})(req, res, next);
}
}
app.module.ts
export class AppModule implements NestModule {
public configure(consumer: MiddlewareConsumer): void {
consumer
.apply(RawBodyMiddleware)
.forRoutes({
path: '/uploadExportFile',
method: RequestMethod.POST,
})
.apply(JsonBodyMiddleware)
.forRoutes('*');
}
}
and you need to disable bodyparser in main.ts
const app = await NestFactory.create(AppModule, { bodyParser: false })
in new version of NestJS is introduced new option raw-body but I have no possibility to test that https://docs.nestjs.com/faq/raw-body#raw-body
frist thing send the content-type application/x-www-form-urlencoded
and sure you have add UseInterceptors Like FileInterceptor
you can import FileInterceptor
if you need to get buffer try use file.buffer
import {FileInterceptor} from "#nestjs/platform-express";
#Post('upload')
#UseInterceptors(FileInterceptor('file'))
async upload(#Req() request: RequestWithUser, #UploadedFile() file) {
if (!file) {
throw new HttpException('File is required', HttpStatus.BAD_REQUEST);
}
// you have file
return await this.storageService.upload(file, request.user);
}
I would like to know how can a server side application receive a file (via POST) and then print its contents on the server side.
The most "up to date" related question here was this one: Dart how to upload image
But it is not working anymore (Uncaught Error: type 'String' is not a subtype of type 'HttpBodyFileUpload' of 'fileUploaded').
EDIT:
This is how I send the file (this method is working fine):
import 'dart:html';
import 'dart:async';
HttpRequest request = new HttpRequest();
final _HOST = "127.0.0.1", _PORT = 8123;
Future sendFile(File file) {
var completer = new Completer(); // No need for a Completer. It will be removed.
Uri uri = new Uri(host: _HOST, port: _PORT);
request.open("POST", uri.toString());
var filename = file.name;
final FormData formData = new FormData();
formData.append('file', filename);
request.onLoadEnd.listen((_) {
completer.complete(request.response);
});
request.send(formData);
return completer.future;
}
The server side (I'm stuck here):
void _handlePost(HttpRequest req) {
HttpBodyHandler.processRequest(req).then((body) {
HttpBodyFileUpload fileUploaded = body.body['file'];
print(fileUploaded.content);
});
}
You are appending the filename instead of the Blob (File) to your FormData object. In Dart it looks like there is a special function for appending blobs called appendBlob(name, blob, [filename]).
import 'dart:io';
import 'dart:async';
void main() {
HttpClient client = new HttpClient();
client.getUrl(Uri.parse('http://api.dartlang.org/docs/releases/latest/dart_io/HttpClientResponse.html'))
.then((HttpClientRequest request) => request.close())
.then((HttpClientResponse response) {
response.listen(print, onError: (e) {
print('error: $e');
});
});
}
The code above doesn't work, using similar method to listen like pipe and fold also throws an exception => Breaking on exception: The null object does not have a method 'cancel'.
Update
Here's the code example for when connect to local machine.
import 'dart:io';
import 'dart:async';
void main() {
HttpServer.bind('127.0.0.1', 8080)
.then((HttpServer server) {
server.listen((HttpRequest request) {
File f = new File('upload.html');
f.openRead().pipe(request.response);
});
HttpClient client = new HttpClient();
client.getUrl(Uri.parse('http://127.0.0.1:8080'))
.then((HttpClientRequest request) => request.close())
.then((HttpClientResponse response) {
response.listen(print, onError: (e) {
print('error: $e');
});
});
});
}
It prints out the bytes first and then throw an exception Breaking on exception: The null object does not have a method 'cancel'.
Dart Editor version 0.7.2_r27268. Dart SDK version 0.7.2.1_r27268. On Windows 64bit machine.
Your example works on my machine.
Please specify your Dart version and other system properties that could help debug the problem.
The code presented looks fine, and I have not been able to reproduce the error on either 0.7.2.1 nor bleeding edge. Do you know whether you network has any kind of proxy setup which could cause a direct HTTP connection to fail? You could try connecting to a server on your local machine instead. If it still fails I suggest opening a bug on https://code.google.com/p/dart/issues/list with detailed information.
Can we use dart to download a file?
For example in python
I'm using the HTTP package a lot. If you want to download a file that is not huge, you could use the HTTP package for a cleaner approach:
import 'package:http/http.dart' as http;
main() {
http.get(url).then((response) {
new File(path).writeAsBytes(response.bodyBytes);
});
}
What Alexandre wrote will perform better for larger files. Consider writing a helper function for that if you find the need for downloading files often.
Shailen's response is correct and can even be a little shorter with Stream.pipe.
import 'dart:io';
main() async {
final request = await HttpClient().getUrl(Uri.parse('http://example.com'));
final response = await request.close();
response.pipe(File('foo.txt').openWrite());
}
The python example linked to in the question involves requesting the contents of example.com and writing the response to a file.
Here is how you can do something similar in Dart:
import 'dart:io';
main() {
var url = Uri.parse('http://example.com');
var httpClient = new HttpClient();
httpClient.getUrl(url)
.then((HttpClientRequest request) {
return request.close();
})
.then((HttpClientResponse response) {
response.transform(new StringDecoder()).toList().then((data) {
var body = data.join('');
print(body);
var file = new File('foo.txt');
file.writeAsString(body).then((_) {
httpClient.close();
});
});
});
}
We can use http.readBytes(url).
await File(path).writeAsBytes(await http.readBytes('https://picsum.photos/200/300/?random'));
Yes, first of all you have to request to file url using http dart library like:
Response response = await get(Uri.parse(link));
after that your Response object (response) will get that file in self and you can simply write the response bytes to a file and that file will be your downloaded file.
as I open file like this:
File file = File('image.jpg')
then we have to send response bytes to this file like this:
file.writeAsBytes(response.bodyBytes);
now you have downloaded a image file successfully.. Congrates.
additional, for example let me show you a sample code to download a image file :
import 'dart:io';
import 'package:http/http.dart';
main(List<String> args) async {
var link =
"https://pps.whatsapp.net/v/t61.24694-
24/72779382_449683642563635_3243701117464346624_n.jpg?ccb=11-
4&oh=23e3bc2ce3f4940a70cb464494bbda76&oe=619B3B8C";
Response response = await get(Uri.parse(link));
File file = File('image.jpg');
file.writeAsBytes(response.bodyBytes);
}
look, this is the code and a file named image.jpg is downloaded at bottom in terminal view is our downloaded image.
screen shot
this is our actual image which we downloaded.
downloaded image