File add API server in Vapor 4

Discover ways to construct a quite simple file add API server utilizing Vapor 4 and URLSession add activity on the shopper aspect.


A easy file add server written in Swift

For this easy file add tutorial we’ll solely use the Vapor Swift package deal as a dependency. 📦

import PackageDescription

let package deal = Bundle(
    identify: "myProject",
    platforms: [
    dependencies: [
        .package(url: "", from: "4.35.0"),
    targets: [
            name: "App",
            dependencies: [
                .product(name: "Vapor", package: "vapor"),
            swiftSettings: [
                .unsafeFlags(["-cross-module-optimization"], .when(configuration: .launch))
        .goal(identify: "Run", dependencies: [.target(name: "App")]),
        .testTarget(identify: "AppTests", dependencies: [
            .target(name: "App"),
            .product(name: "XCTVapor", package: "vapor"),

You may setup the venture with the required recordsdata utilizing the Vapor toolbox, alternatively you possibly can create every thing by hand utilizing the Swift Bundle Supervisor, lengthy story quick, we simply want a starter Vapor venture with out extra dependencies. Now when you open the Bundle.swift file utilizing Xcode, we will setup our routes by altering the configure.swift file.

import Vapor

public func configure(_ app: Software) throws {

    app.middleware.use(FileMiddleware(publicDirectory: app.listing.publicDirectory))

    app.routes.defaultMaxBodySize = "10mb"

    app.submit("add") { req -> EventLoopFuture<String> in
        let key = attempt req.question.get(String.self, at: "key")
        let path = req.utility.listing.publicDirectory + key
        return req.physique.acquire()
            .unwrap(or: Abort(.noContent))
            .flatMap { req.fileio.writeFile($0, at: path) }
            .map { key }

First we use the FileMiddleware, this may permit us to server recordsdata utilizing the Public listing inside our venture folder. If you do not have a listing named Public, please create one, for the reason that file add server will want that. Remember to present correct file system permissions if mandatory, in any other case we can’t have the ability to write our information contained in the listing. 📁

The following factor that we set is the default most physique dimension. This property can restrict the quantity of information that our server can settle for, you do not actually need to use this technique for giant recordsdata as a result of uploaded recordsdata will likely be saved within the system reminiscence earlier than we write them to the disk.

If you wish to add massive recordsdata to the server it is best to take into account streaming the file as an alternative of accumulating the file information from the HTTP physique. The streaming setup would require a bit extra work, nevertheless it’s not that sophisticated, in case you are enthusiastic about that answer, it is best to learn the Recordsdata API and the physique streaming part utilizing official Vapor docs web site.

This time we simply desire a useless easy file add API endpoint, that collects the incoming information utilizing the HTTP physique right into a byte buffer object, then we merely write this buffer utilizing the fileio to the disk, utilizing the given key from the URL question parameters. If every thing was finished with out errors, we will return the important thing for the uploaded file.

File add duties utilizing the URLSession API

The Basis frameworks offers us a pleasant API layer for widespread networking duties. We will use the URLSession uploadTask technique to ship a brand new URLRequest with an information object to a given server, however IMHO this API is kind of unusual, as a result of the URLRequest object already has a httpBody property, however you must explicitly cross a “from: Knowledge?” argument once you assemble the duty. However why? 🤔

import Basis

extension URLSession {

    func uploadTask(with request: URLRequest, completionHandler: @escaping (Knowledge?, URLResponse?, Error?) -> Void) -> URLSessionUploadTask {
        uploadTask(with: request, from: request.httpBody, completionHandler: completionHandler)

Anyway, I made a bit extension technique, so after I create the URLRequest I can set the httpBody property of it and safely cross it earlier than the completion block and use the contents because the from parameter. Very unusual API design alternative from Apple… 🤐

We will put this little snippet right into a easy executable Swift package deal (or after all we will create a whole utility) to check our add server. In our case I will place every thing right into a important.swift file.

import Basis
import Dispatch

extension URLSession {

    func uploadTask(with request: URLRequest, completionHandler: @escaping (Knowledge?, URLResponse?, Error?) -> Void) -> URLSessionUploadTask {
        uploadTask(with: request, from: request.httpBody, completionHandler: completionHandler)

let fileData = attempt Knowledge(contentsOf: URL(fileURLWithPath: "/Customers/[user]]/[file].png"))
var request = URLRequest(url: URL(string: "http://localhost:8080/add?key=(UUID().uuidString).png")!)
request.httpMethod = "POST"
request.httpBody = fileData

let activity = URLSession.shared.uploadTask(with: request) { information, response, error in
    guard error == nil else {
    guard let response = response as? HTTPURLResponse else {
        fatalError("Invalid response")
    guard response.statusCode == 200 else {
        fatalError("HTTP standing error: (response.statusCode)")
    guard let information = information, let end result = String(information: information, encoding: .utf8) else {
        fatalError("Invalid or lacking HTTP information")
    print(end result)


The above instance makes use of the Dispatch framework to attend till the asynchronous file add finishes. It’s best to change the situation (and the extension) of the file if mandatory earlier than you run this script. Since we outlined the add route as a POST endpoint, now we have to set the httpMethod property to match this, additionally we retailer the file information within the httpBody variable earlier than we create our activity. The add URL ought to comprise a key, that the server can use as a reputation for the file. You may add extra properties after all or use header values to test if the person has correct authorization to carry out the add operation. Then we name the add activity extension technique on the shared URLSession property. The great factor about uploadTask is you can run them on the background if wanted, that is fairly useful if it involves iOS improvement. 📱

Contained in the completion handler now we have to test for a number of issues. To start with if there was an error, the add will need to have failed, so we name the fatalError technique to interrupt execution. If the response was not a sound HTTP response, or the standing code was not okay (200) we additionally cease. Lastly we need to retrieve the important thing from the response physique so we test the information object and convert it to a utf8 string if doable. Now we will use the important thing mixed with the area of the server to entry the uploaded file, this time I simply printed out the end result, however hey, that is only a demo, in an actual world utility you may need to return a JSON response with extra information. 😅

Vanilla JavaScript file uploader

Yet one more factor… you should utilize Leaf and a few Vanilla JavaScript to add recordsdata utilizing the newly created add endpoint. Really it is very easy to implement a brand new endpoint and render a Leaf template that does the magic. You will want some fundamental HTML and some strains of JS code to submit the contents of the file as an array buffer. It is a fundamental instance.

<!DOCTYPE html>
    <meta charset="utf-8">
    <meta identify="viewport" content material="width=device-width, initial-scale=1">
    <title>File add</title>
      <h1>File add</h1>
      <enter kind="file" id="file" identify="file" settle for="picture/*" /><br><br>
      <img id="preview" src="" width="256px">
        doc.getElementById('file').addEventListener("change", uploadImage);

        operate uploadImage() {
            var xhr = new XMLHttpRequest();
  "POST", "/add?key=check.png", true);
            xhr.onreadystatechange = operate() {
                if(xhr.readyState == 4 && xhr.standing == 200) {
                    doc.getElementById('preview').src = "/" + this.responseText;

            var file = doc.getElementById('file').recordsdata[0];
            if (file) {
                var reader = new FileReader();
                reader.onload = operate() {
                    xhr.ship(reader.end result);

As you possibly can see it is a normal xhr request mixed with the FileReader JavaScript API. We use the FileReader to transform our enter to a binary information, this manner our server can write it to the file system within the anticipated format. Most often persons are utilizing a multipart-encoded kind to entry recordsdata on the server, however when you must work with an API you may as well switch uncooked file information. If you wish to study extra about XHR requests and AJAX calls, it is best to learn my earlier article.

I even have a submit about totally different file add strategies utilizing normal HTML types and a Vapor 4 server as a backend. I hope you will discover the proper answer that you just want on your utility. 👍

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