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 line with the requirements, the Content material-Sort and Content material-Size headers can be utilized to have a greater understanding concerning the information contained in the physique of the HTTP request.
Trendy internet servers can mechanically ship again these headers primarily based on the item you come back in a request handler perform. 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 whats up endpoint utilizing cURL with the -i flag, the output will include a bit extra details about the response. ℹ️
router.get("whats up") { _ in "whats up" }
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 kind utilizing our Swift code. The content-length is 5, as a result of the character depend of whats up 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 correct content material kind header to the response and encode some object right into a HTTP response information. Not all the things is response encodable and decodable by default, however you possibly can 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 by means of 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 kind extensions. Subsequent it’s a must to setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you possibly can 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.put up("foo") { req async throws -> Foo in
guard let foo = attempt? req.decode(as: Foo.self) else {
throw HBHTTPError(.badRequest, message: "Invalid request physique.")
}
return foo
}
}
}As you possibly can see the kind of the returned content material is now correctly set to software/json and the size can also be supplied by default. We had been additionally capable of decode the Foo object from the request physique and mechanically encode the item after we returned with it.
Codable routing works like magic and these days it is a fairly customary strategy if it involves server-side Swift frameworks. Enjoyable truth: 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 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 in addition present extra headers. If you need to know extra, I extremely suggest to try the JSONCoding.swift file contained in the framework. 😉
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 best way there’s a higher manner utilizing SwiftHtml, however I would wish to focus extra on the underlying information switch mechanism and the enctype attribute. There are 3 doable, however solely two helpful values of the encoding kind:
- software/x-www-form-urlencoded
- multipart/form-data
URL encoding and decoding is supported out of the field when utilizing HummingbirdFoundation, this can be 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 is predicated on the multipart strategy, which has no built-in help in Hummingbird, however you need to use 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 how you can add recordsdata 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 primarily based encoding and decoding
First now we have to implement a customized request decoder and a response encoder. Within the decoder, we’ll test the Content material-Sort 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 subject. Here is how one can implement it:
struct AppDecoder: HBRequestDecoder {
func decode<T>(
_ kind: T.Sort,
from req: HBRequest
) throws -> T the place T: Decodable {
change req.headers["content-type"].first {
case "software/json", "software/json; charset=utf-8":
return attempt JSONDecoder().decode(kind, from: req)
case "software/x-www-form-urlencoded":
return attempt URLEncodedFormDecoder().decode(kind, from: req)
default:
throw HBHTTPError(.badRequest)
}
}
}
struct AppEncoder: HBResponseEncoder {
func encode<T>(
_ worth: T,
from req: HBRequest
) throws -> HBResponse the place T: Encodable {
change req.headers["accept"].first {
case "software/json":
return attempt JSONEncoder().encode(worth, from: req)
case "software/x-www-form-urlencoded":
return attempt URLEncodedFormEncoder().encode(worth, from: req)
default:
throw HBHTTPError(.badRequest)
}
}
}Now if you happen to change the configuration and use the AppEncoder & AppDecoder you need to have the ability to reply primarily based on the Settle for header and course of the enter primarily based on the Content material-Sort 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.put up("foo") { req async throws -> Foo in
guard let foo = attempt? 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… 👾
# ought to return JSON encoded information
curl -i -X POST http://localhost:8080/foo
-H "Content material-Sort: 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-Sort: 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-Sort: software/json"
-H "Settle for: multipart/form-data"
--data-raw '{"bar": "bar", "baz": 42}'
So, primarily based on this text you need to have the ability to implement help to much more content material varieties by merely extending the app encoder and decoder. After all you may need to import some extra package deal dependencies, however that is high-quality.
Uncooked requests and responses
Yet one more little factor, earlier than I finish this text: you possibly can entry the uncooked request physique information and ship again a uncooked response utilizing the HBResponse object like this:
router.put up("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 attempt await chunk in sequence {
print(chunk)
}
}
guard let information = "whats up".information(utilizing: .utf8) else {
throw HBHTTPError(.internalServerError)
}
return .init(
standing: .okay,
headers: .init(),
physique: .byteBuffer(.init(information: information))
)
}For smaller requests, you need to use the req.physique.buffer property and switch it right into a Information kind if wanted. Hummingbird has nice help for the brand new Swift Concurreny API, so you need to use 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 want to speak with my API utilizing REST (JSON) and add recordsdata 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 will ultimately face the necessity of file add and that will not work with URL encoded varieties, however solely with multipart.
In conclusion I would say that the excellent news is that now we 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… 🙃