Encoding and decoding knowledge utilizing the Hummingbird framework


HTTP is all about sending and receiving knowledge 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 knowledge 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 knowledge contained in the physique of the HTTP request.

Fashionable internet servers can routinely ship again these headers primarily based on the thing you come back in a request handler operate. That is the case with Hummingbird, it has built-in encoding and decoding help, which makes the information transformation course of actually easy.

For instance if we setup the next route handler and name the hey endpoint utilizing cURL with the -i flag, the output will comprise a bit extra details about the response. โ„น๏ธ

router.get("hey") { _ in "hey" }
        

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 hey is 5.

There are another headers, however ignore these, the attention-grabbing 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 right content material sort header to the response and encode some object right into a HTTP response knowledge. Not all the pieces is response encodable and decodable by default, however you may encode String objects in Hummingbird by default. ๐Ÿ‘

Encoding and decoding JSON objects

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

First it’s important to import the HummingbirdFoundation library, since it’s a standalone helper software constructed across the Basis framework, and that bundle comprises the Codable sort extensions. Subsequent it’s important to setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you may simply rework incoming HTTP physique objects into Swift knowledge constructions and return with them as properly. Let me present you a fast instance. โคต๏ธ

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.submit("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 also be offered by default. We have been additionally in a position to decode the Foo object from the request physique and routinely encode the thing after we returned with it.

Codable routing works like magic and these days it is a fairly customary method if it involves server-side Swift frameworks. Enjoyable reality: this method was initially ‘invented’ for Swift by the builders of the Kitura framework. Thanks. ๐Ÿ™

The HBResponseCodable and the HBResponseEncodable protocols are the fundamental constructing blocks and the HBRequestDecoder and the HBResponseEncoder are accountable for this magic. They make it doable to decode a Decodable object from a HBRequest and encode issues right into a HBResponse object and likewise present further headers. If you need to know extra, I extremely advocate to try the JSONCoding.swift file contained in the framework. ๐Ÿ˜‰

Encoding and decoding HTML varieties

I do not need to get an excessive amount of into the main points of constructing varieties 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 knowledge switch mechanism and the enctype attribute. There are 3 doable, 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 knowledge transformation.

decoder = URLEncodedFormDecoder()
encoder = URLEncodedFormEncoder()

In order that’s one technique to course of a URL encoded kind, the opposite model is predicated on the multipart method, which has no built-in help in Hummingbird, however you should utilize the multipart-kit library from the Vapor framework to course of such varieties. You will discover a working instance right here. I even have an article about tips on how to add information utilizing multipart kind knowledge requests. So there are many assets on the market, that is why I will not embody an instance on this article. ๐Ÿ˜…

Header primarily based encoding and decoding

First we have now to implement a customized request decoder and a response encoder. Within the decoder, we’ll examine the Content material-Kind header for a given request and decode the HTTP physique primarily based on that. The encoder will do the very same factor, however the response physique output goes to rely upon the Settle for header area. Here 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 if you happen to change the configuration and use the AppEncoder & AppDecoder you must have the ability to reply primarily based on the Settle for header and course of the enter primarily based 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.submit("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 at liberty to mess around with some cURL snippets… ๐Ÿ‘พ

# ought to return JSON encoded knowledge
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 knowledge
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, primarily based on this text you must have the ability to implement help to much more content material varieties by merely extending the app encoder and decoder. In fact you might need to import some further bundle dependencies, however that is advantageous.

Uncooked requests and responses

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

router.submit("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 knowledge = "hey".knowledge(utilizing: .utf8) else {
        throw HBHTTPError(.internalServerError)
    }
    
    return .init(
        standing: .okay,
        headers: .init(),
        physique: .byteBuffer(.init(knowledge: knowledge))
    )
}

For smaller requests, you should utilize 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 utilize the sequence on the physique stream if you happen to 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 desire 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 if you happen to submit HTML varieties, you may ultimately face the necessity of file add and that will not work with URL encoded varieties, however solely with multipart.

In conclusion I might say that the excellent news is that we have now 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 actually need. Anyway, competitors is an efficient factor to have on this case, as a result of hopefully each frameworks will evolve for good… ๐Ÿ™ƒ

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