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Encoding and decoding information utilizing the Hummingbird framework


HTTP is all about sending and receiving information over the community. Initially it was solely utilized to switch HTML paperwork, however these days we use HTTP to switch CSS, JavaScript, JSON and lots of different information varieties. In accordance with the requirements, the Content material-Kind and Content material-Size headers can be utilized to have a greater understanding in regards to the information contained in the physique of the HTTP request.

Fashionable internet servers can mechanically ship again these headers based mostly on the article you come in a request handler perform. That is the case with Hummingbird, it has built-in encoding and decoding help, which makes the info transformation course of actually easy.

For instance if we setup the next route handler and name the good day endpoint utilizing cURL with the -i flag, the output will comprise a bit extra details about the response. ℹ️

router.get("good day") { _ in "good day" }
        

There are some fundamental headers within the response, the content-type header comprises the kind of the physique, which is at present a plain textual content with an UTF-8 encoded string, since we have returned a String sort utilizing our Swift code. The content-length is 5, as a result of the character rely of good day is 5.

There are another headers, however ignore these, the fascinating half for us is the content-type header, and the way it’s injected into the response. Each Hummingbird software has an encoder and a decoder property. The default values for these are NullEncoder and NullDecoder. The encoders can magically add the correct content material sort header to the response and encode some object right into a HTTP response information. Not every little thing is response encodable and decodable by default, however you may encode String objects in Hummingbird by default. 👍

Encoding and decoding JSON objects

Lots of the server-side Swift techniques are used to create JSON-based RESTful API backends for cell frontends. Hummingbird may also help you with this, because it has built-in encoding and decoding help for JSON objects via the Codable protocol.

First it’s a must to import the HummingbirdFoundation library, since it’s a standalone helper software constructed across the Basis framework, and that package deal comprises the Codable sort extensions. Subsequent it’s a must to setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you may simply remodel incoming HTTP physique objects into Swift information constructions and return with them as nicely. Let me present you a fast instance. ⤵️

import Hummingbird
import HummingbirdFoundation

struct Foo: Codable {
    let bar: String
    let baz: Int
}

extension Foo: HBResponseCodable {}


extension HBApplication {

    func configure(_ args: AppArguments) throws {
        
        decoder = JSONDecoder()
        encoder = JSONEncoder()
        
        router.publish("foo") { req async throws -> Foo in
            guard let foo = strive? req.decode(as: Foo.self) else {
                throw HBHTTPError(.badRequest, message: "Invalid request physique.")
            }
            return foo
        }
    }

    
}

As you may see the kind of the returned content material is now correctly set to software/json and the size can be supplied by default. We had been additionally in a position to decode the Foo object from the request physique and mechanically encode the article after we returned with it.

Codable routing works like magic and these days it is a fairly commonplace strategy if it involves server-side Swift frameworks. Enjoyable reality: this strategy was initially ‘invented’ for Swift by the builders of the Kitura framework. Thanks. 🙏

The HBResponseCodable and the HBResponseEncodable protocols are the fundamental constructing blocks and the HBRequestDecoder and the HBResponseEncoder are liable for this magic. They make it attainable to decode a Decodable object from a HBRequest and encode issues right into a HBResponse object and in addition present further headers. If you need to know extra, I extremely suggest to try the JSONCoding.swift file contained in the framework. 😉

Encoding and decoding HTML kinds

I do not need to get an excessive amount of into the small print of constructing kinds utilizing HTML code, by the way in which there’s a higher approach utilizing SwiftHtml, however I might prefer to focus extra on the underlying information switch mechanism and the enctype attribute. There are 3 attainable, however solely two helpful values of the encoding sort:

  • software/x-www-form-urlencoded
  • multipart/form-data

URL encoding and decoding is supported out of the field when utilizing HummingbirdFoundation, it is a easy wrapper across the URL encoding mechanism to simply help information transformation.

decoder = URLEncodedFormDecoder()
encoder = URLEncodedFormEncoder()

In order that’s one method to course of a URL encoded type, the opposite model relies on the multipart strategy, which has no built-in help in Hummingbird, however you should use the multipart-kit library from the Vapor framework to course of such kinds. You’ll find a working instance right here. I even have an article about how you can add information utilizing multipart type information requests. So there are many assets on the market, that is why I will not embody an instance on this article. 😅

Header based mostly encoding and decoding

First we now have to implement a customized request decoder and a response encoder. Within the decoder, we will examine the Content material-Kind header for a given request and decode the HTTP physique based mostly on that. The encoder will do the very same factor, however the response physique output goes to rely on the Settle for header subject. This is how one can implement it:

struct AppDecoder: HBRequestDecoder {
    
    func decode<T>(
        _ sort: T.Kind,
        from req: HBRequest
    ) throws -> T the place T: Decodable {
        swap req.headers["content-type"].first {
        case "software/json", "software/json; charset=utf-8":
            return strive JSONDecoder().decode(sort, from: req)
        case "software/x-www-form-urlencoded":
            return strive URLEncodedFormDecoder().decode(sort, from: req)
        default:
            throw HBHTTPError(.badRequest)
        }
    }
}

struct AppEncoder: HBResponseEncoder {

    func encode<T>(
        _ worth: T,
        from req: HBRequest
    ) throws -> HBResponse the place T: Encodable {
        swap req.headers["accept"].first {
        case "software/json":
            return strive JSONEncoder().encode(worth, from: req)
        case "software/x-www-form-urlencoded":
            return strive URLEncodedFormEncoder().encode(worth, from: req)
        default:
            throw HBHTTPError(.badRequest)
        }
    }
}

Now in case you change the configuration and use the AppEncoder & AppDecoder it’s best to be capable of reply based mostly on the Settle for header and course of the enter based mostly on the Content material-Kind header.

import Hummingbird
import HummingbirdFoundation

struct Foo: Codable {
    let bar: String
    let baz: Int
}

extension Foo: HBResponseEncodable {}
extension Foo: HBResponseCodable {}

extension HBApplication {

    func configure(_ args: AppArguments) throws {
        
        decoder = AppDecoder()
        encoder = AppEncoder()
        
        router.publish("foo") { req async throws -> Foo in
            guard let foo = strive? req.decode(as: Foo.self) else {
                throw HBHTTPError(.badRequest, message: "Invalid request physique.")
            }
            return foo
        }
    }
}

Be happy to mess around with some cURL snippets… 👾

# ought to return JSON encoded information
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/x-www-form-urlencoded" 
    -H "Settle for: software/json" 
    --data-raw 'bar=bar&baz=42'

# ought to return URL encoded information
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/json" 
    -H "Settle for: software/x-www-form-urlencoded" 
    --data-raw '{"bar": "bar", "baz": 42}'

# ought to return with a 400 standing code
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/json" 
    -H "Settle for: multipart/form-data" 
    --data-raw '{"bar": "bar", "baz": 42}'

So, based mostly on this text it’s best to be capable of implement help to much more content material varieties by merely extending the app encoder and decoder. After all you might need to import some further package deal dependencies, however that is fantastic.

Uncooked requests and responses

Another little factor, earlier than I finish this text: you may entry the uncooked request physique information and ship again a uncooked response utilizing the HBResponse object like this:

router.publish("foo") { req async throws -> HBResponse in
    
    if let buffer = req.physique.buffer {
        let rawInputData = buffer.getData(
            at: 0,
            size: buffer.readableBytes
        )
        print(rawInputData)
    }
    
    
    if let sequence = req.physique.stream?.sequence {
        for strive await chunk in sequence {
            print(chunk)
        }
    }
    
    guard let information = "good day".information(utilizing: .utf8) else {
        throw HBHTTPError(.internalServerError)
    }
    
    return .init(
        standing: .okay,
        headers: .init(),
        physique: .byteBuffer(.init(information: information))
    )
}

For smaller requests, you should use the req.physique.buffer property and switch it right into a Knowledge sort if wanted. Hummingbird has nice help for the brand new Swift Concurreny API, so you should use the sequence on the physique stream in case you want chunked reads. Now just one query left:

What varieties ought to I help?

The reply is straightforward: it relies upon. Like actually. These days I began to ditch multipart encoding and I want to speak with my API utilizing REST (JSON) and add information as uncooked HTTP physique. I by no means actually needed to help URL encoding, as a result of in case you submit HTML kinds, you will finally face the necessity of file add and that will not work with URL encoded kinds, however solely with multipart.

In conclusion I might say that the excellent news is that we now have loads of alternatives and if you wish to present help for many of those varieties you do not have to reinvent the wheel in any respect. The multipart-kit library is constructed into Vapor 4, however that is one of many causes I began to love Hummingbird a bit extra, as a result of I can solely embody what I really want. Anyway, competitors is an efficient factor to have on this case, as a result of hopefully each frameworks will evolve for good… 🙃

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