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 keeping with the requirements, the Content material-Sort and Content material-Size headers can be utilized to have a greater understanding concerning the knowledge contained in the physique of the HTTP request.
Fashionable net servers can routinely ship again these headers primarily based on the item 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 hi there endpoint utilizing cURL with the -i flag, the output will comprise a bit extra details about the response. ℹ️
router.get("hi there") { _ in "hi there" }
There are some primary headers within the response, the content-type header comprises the kind of the physique, which is at the moment 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 depend of hi there 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 sort header to the response and encode some object right into a HTTP response knowledge. Not all the things is response encodable and decodable by default, however you’ll be able to encode String objects in Hummingbird by default. 👍
Encoding and decoding JSON objects
Lots of the server-side Swift programs 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 way of the Codable protocol.
First you need to import the HummingbirdFoundation library, since it’s a standalone helper instrument constructed across the Basis framework, and that package deal comprises the Codable sort extensions. Subsequent you need to setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you’ll be able to simply rework incoming HTTP physique objects into Swift knowledge buildings 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 = strive? req.decode(as: Foo.self) else {
throw HBHTTPError(.badRequest, message: "Invalid request physique.")
}
return foo
}
}
}As you’ll be able to see the kind of the returned content material is now correctly set to software/json and the size can be supplied by default. We have been additionally capable of decode the Foo object from the request physique and routinely encode the item after we returned with it.
Codable routing works like magic and these days it is a fairly commonplace 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. 🙏
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 potential to decode a Decodable object from a HBRequest and encode issues right into a HBResponse object and in addition present further headers. If you want to know extra, I extremely advocate 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 way in which there’s a higher means utilizing SwiftHtml, however I would wish to focus extra on the underlying knowledge switch mechanism and the enctype attribute. There are 3 potential, 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 option to course of a URL encoded kind, the opposite model relies on the multipart method, which has no built-in help in Hummingbird, however you should use the multipart-kit library from the Vapor framework to course of such varieties. You’ll find a working instance right here. I even have an article about the best way to add information utilizing multipart kind knowledge requests. So there are many sources on the market, that is why I will not embrace an instance on this article. 😅
Header primarily based encoding and decoding
First we’ve to implement a customized request decoder and a response encoder. Within the decoder, we’ll examine 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(
_ sort: T.Sort,
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(
_ 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 for those who change the configuration and use the AppEncoder & AppDecoder it’s best 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 = 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 knowledge
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 knowledge
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 it’s best to have the ability to 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 nice.
Uncooked requests and responses
Yet another little factor, earlier than I finish this text: you’ll be able to entry the uncooked request physique knowledge 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 strive await chunk in sequence {
print(chunk)
}
}
guard let knowledge = "hi there".knowledge(utilizing: .utf8) else {
throw HBHTTPError(.internalServerError)
}
return .init(
standing: .okay,
headers: .init(),
physique: .byteBuffer(.init(knowledge: knowledge))
)
}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 for those who 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 choose 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 for those who 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 we’ve 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 embrace what I actually need. Anyway, competitors is an effective factor to have on this case, as a result of hopefully each frameworks will evolve for good… 🙃
