File add API server in Vapor 4

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


A easy file add server written in Swift

For this straightforward file add tutorial we’ll solely use the Vapor Swift bundle as a dependency. πŸ“¦

import PackageDescription

let bundle = Package deal(
    title: "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(title: "Run", dependencies: [.target(name: "App")]),
        .testTarget(title: "AppTests", dependencies: [
            .target(name: "App"),
            .product(name: "XCTVapor", package: "vapor"),

You may setup the undertaking with the required recordsdata utilizing the Vapor toolbox, alternatively you’ll be able to create all the pieces by hand utilizing the Swift Package deal Supervisor, lengthy story quick, we simply want a starter Vapor undertaking with out further dependencies. Now should you open the Package deal.swift file utilizing Xcode, we are able to setup our routes by altering the configure.swift file.

import Vapor

public func configure(_ app: Utility) throws {

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

    app.routes.defaultMaxBodySize = "10mb"

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

First we use the FileMiddleware, this can enable us to server recordsdata utilizing the Public listing inside our undertaking folder. If you do not have a listing named Public, please create one, because the file add server will want that. Do not forget to present correct file system permissions if essential, in any other case we can’t have the ability to write our information contained in the listing. πŸ“

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 methodology for giant recordsdata as a result of uploaded recordsdata shall be saved within the system reminiscence earlier than we write them to the disk.

If you wish to add giant recordsdata to the server it is best to think about streaming the file as an alternative of gathering the file information from the HTTP physique. The streaming setup would require a bit extra work, but it surely’s not that sophisticated, if you’re desirous 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 need a lifeless 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 all the pieces was executed with out errors, we are able to return the important thing for the uploaded file.

File add duties utilizing the URLSession API

The Basis frameworks provides us a pleasant API layer for frequent networking duties. We will use the URLSession uploadTask methodology to ship a brand new URLRequest with a knowledge object to a given server, however IMHO this API is sort of unusual, as a result of the URLRequest object already has a httpBody property, however it’s important to explicitly move a “from: Knowledge?” argument whenever you assemble the duty. However why? πŸ€”

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 slightly extension methodology, so after I create the URLRequest I can set the httpBody property of it and safely move 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 bundle (or after all we are able to create a complete software) to check our add server. In our case I will place all the pieces right into a foremost.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 = strive 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 job = 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 outcome = String(information: information, encoding: .utf8) else {
        fatalError("Invalid or lacking HTTP information")


The above instance makes use of the Dispatch framework to attend till the asynchronous file add finishes. It is best to change the placement (and the extension) of the file if essential 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 job. 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 job extension methodology on the shared URLSession property. The good factor about uploadTask is which you can run them on the background if wanted, that is fairly useful if it involves iOS improvement. πŸ“±

Contained in the completion handler now we have to test for a couple of issues. To start with if there was an error, the add will need to have failed, so we name the fatalError methodology 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 info object and convert it to a utf8 string if attainable. Now we are able to use the important thing mixed with the area of the server to entry the uploaded file, this time I simply printed out the outcome, however hey, that is only a demo, in an actual world software you may need to return a JSON response with further information. πŸ˜…

Vanilla JavaScript file uploader

Yet one more factor… you need to use Leaf and a few Vanilla JavaScript to add recordsdata utilizing the newly created add endpoint. Truly it is very easy to implement a brand new endpoint and render a Leaf template that does the magic. You may want some primary HTML and some strains of JS code to submit the contents of the file as an array buffer. This can be a primary instance.

<!DOCTYPE html>
    <meta charset="utf-8">
    <meta title="viewport" content material="width=device-width, initial-scale=1">
    <title>File add</title>
      <h1>File add</h1>
      <enter kind="file" id="file" title="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=take a look at.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() {

As you’ll be able to see it is an ordinary xhr request mixed with the FileReader JavaScript API. We use the FileReader to transform our enter to a binary information, this fashion our server can write it to the file system within the anticipated format. Generally individuals are utilizing a multipart-encoded type to entry recordsdata on the server, however when it’s important to work with an API you too can 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 publish about completely different file add strategies utilizing commonplace HTML kinds and a Vapor 4 server as a backend. I hope you may discover the suitable answer that you simply want to your software. πŸ‘

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