Kitten.jl

About

Kitten is a micro-framework built on top of the HTTP.jl library.

Features

• Straightforward routing
• Real-time Metrics Dashboard
• Auto-generated swagger documentation
• Out-of-the-box JSON serialization & deserialization (customizable)
• Type definition support for path parameters
• Request Extractors
• Multiple Instance Support
• Multithreading support
• Websockets, Streaming, and Server-Sent Events
• Cron Scheduling (on endpoints & functions)
• Middleware chaining (at the application, router, and route levels)
• Static & Dynamic file hosting
• Templating Support
• Plotting Support
• Protocol Buffer Support
• Route tagging
• Repeat tasks

Installation

pkg> add Kitten

Minimalistic Example

Create a web-server with very few lines of code

using Kitten
using HTTP

@get "/greet" function(req::HTTP.Request)
    return "hello world!"
end

# start the web server
serve()

Handlers

Handlers are used to connect your code to the server in a clean & straightforward way. They assign a url to a function and invoke the function when an incoming request matches that url.

• Handlers can be imported from other modules and distributed across multiple files for better organization and modularity
• All handlers have equivalent macro & function implementations and support do..end block syntax
• The type of first argument is used to identify what kind of handler is being registered
• This package assumes it's a Request handler by default when no type information is provided

There are 3 types of supported handlers:

• Request Handlers
• Stream Handlers
• Websocket Handlers

using HTTP
using Kitten

# Request Handler
@get "/" function(req::HTTP.Request)
    ...
end

# Stream Handler
@stream "/stream" function(stream::HTTP.Stream)
    ...
end

# Websocket Handler
@websocket "/ws" function(ws::HTTP.WebSocket)
    ...
end

They are just functions which means there are many ways that they can be expressed and defined. Below is an example of several different ways you can express and assign a Request handler.

@get "/greet" function()
    "hello world!"
end

@get("/gruessen") do
    "Hallo Welt!"
end

@get "/saluer" () -> begin
    "Bonjour le monde!"
end

@get "/saludar" () -> "¡Hola Mundo!"
@get "/salutare" f() = "ciao mondo!"

# This function can be declared in another module
function subtract(req, a::Float64, b::Float64)
  return a - b
end

# register foreign request handlers like this
@get "/subtract/{a}/{b}" subtract

More Handler Docs

Request Handlers

Request handlers are used to handle HTTP requests. They are defined using macros or their function equivalents, and accept a HTTP.Request object as the first argument. These handlers support both function and do-block syntax.

• The default Handler when no type information is provided
• Routing Macros: @get, @post, @put, @patch, @delete, @route
• Routing Functions: get(), post(), put(), patch(), delete(), route()

Stream Handlers

Stream handlers are used to stream data. They are defined using the @stream macro or the stream() function and accept a HTTP.Stream object as the first argument. These handlers support both function and do-block syntax.

• @stream and stream() don't require a type definition on the first argument, they assume it's a stream.
• Stream handlers can be assigned with standard routing macros & functions: @get, @post, etc
• You need to explicitly include the type definition so Kitten can identify this as a Stream handler

Websocket Handlers

Websocket handlers are used to handle websocket connections. They are defined using the @websocket macro or the websocket() function and accept a HTTP.WebSocket object as the first argument. These handlers support both function and do-block syntax.

• @websocket and websocket() don't require a type definition on the first argument, they assume it's a websocket.
• Websocket handlers can also be assigned with the @get macro or get() function, because the websocket protocol requires a GET request to initiate the handshake.
• You need to explicitly include the type definition so Kitten can identify this as a Websocket handler

Routing Macro & Function Syntax

There are two primary ways to register your request handlers: the standard routing macros or the routing functions which utilize the do-block syntax.

For each routing macro, we now have a an equivalent routing function

@get    -> get()
@post   -> post()
@put    -> put()
@patch  -> patch()
@delete -> delete()
@route  -> route()

The only practical difference between the two is that the routing macros are called during the precompilation stage, whereas the routing functions are only called when invoked. (The routing macros call the routing functions under the hood)

# Routing Macro syntax
@get "/add/{x}/{y}" function(request::HTTP.Request, x::Int, y::Int)
    x + y
end

# Routing Function syntax
get("/add/{x}/{y}") do request::HTTP.Request, x::Int, y::Int
    x + y
end

Render Functions

Kitten, by default, automatically identifies the Content-Type of the return value from a request handler when building a Response. This default functionality is quite useful, but it does have an impact on performance. In situations where the return type is known, It's recommended to use one of the pre-existing render functions to speed things up.

Here's a list of the currently supported render functions: html, text, json, file, xml, js, css, binary

Below is an example of how to use these functions:

using Kitten

get("/html") do
    html("<h1>Hello World</h1>")
end

get("/text") do
    text("Hello World")
end

get("/json") do
    json(Dict("message" => "Hello World"))
end

serve()

In most cases, these functions accept plain strings as inputs. The only exceptions are the binary function, which accepts a Vector{UInt8}, and the json function which accepts any serializable type.

• Each render function accepts a status and custom headers.
• The Content-Type and Content-Length headers are automatically set by these render functions

Path parameters

Path parameters are declared with braces and are passed directly to your request handler.

using Kitten

# use path params without type definitions (defaults to Strings)
@get "/add/{a}/{b}" function(req, a, b)
    return parse(Float64, a) + parse(Float64, b)
end

# use path params with type definitions (they are automatically converted)
@get "/multiply/{a}/{b}" function(req, a::Float64, b::Float64)
    return a * b
end

# The order of the parameters doesn't matter (just the name matters)
@get "/subtract/{a}/{b}" function(req, b::Int64, a::Int64)
    return a - b
end

# start the web server
serve()

Query parameters

Query parameters can be declared directly inside of your handlers signature. Any parameter that isn't mentioned inside the route path is assumed to be a query parameter.

• If a default value is not provided, it's assumed to be a required parameter

@get "/query" function(req::HTTP.Request, a::Int, message::String="hello world")
    return (a, message)
end

Alternatively, you can use the queryparams() function to extract the raw values from the url as a dictionary.

@get "/query" function(req::HTTP.Request)
    return queryparams(req)
end

HTML Forms

Use the formdata() function to extract and parse the form data from the body of a request. This function returns a dictionary of key-value pairs from the form

using Kitten

# Setup a basic form
@get "/" function()
    html("""
    <form action="/form" method="post">
        <label for="firstname">First name:</label><br>
        <input type="text" id="firstname" name="firstname"><br>
        <label for="lastname">Last name:</label><br>
        <input type="text" id="lastname" name="lastname"><br><br>
        <input type="submit" value="Submit">
    </form>
    """)
end

# Parse the form data and return it
@post "/form" function(req)
    data = formdata(req)
    return data
end

serve()

Return JSON

All objects are automatically deserialized into JSON using the JSON3 library

using Kitten
using HTTP

@get "/data" function(req::HTTP.Request)
    return Dict("message" => "hello!", "value" => 99.3)
end

# start the web server
serve()

Deserialize & Serialize custom structs

Kitten provides some out-of-the-box serialization & deserialization for most objects but requires the use of StructTypes when converting structs

using Kitten
using HTTP
using StructTypes

struct Animal
    id::Int
    type::String
    name::String
end

# Add a supporting struct type definition so JSON3 can serialize & deserialize automatically
StructTypes.StructType(::Type{Animal}) = StructTypes.Struct()

@get "/get" function(req::HTTP.Request)
    # serialize struct into JSON automatically (because we used StructTypes)
    return Animal(1, "cat", "whiskers")
end

@post "/echo" function(req::HTTP.Request)
    # deserialize JSON from the request body into an Animal struct
    animal = json(req, Animal)
    # serialize struct back into JSON automatically (because we used StructTypes)
    return animal
end

# start the web server
serve()

Extractors

Kitten comes with several built-in extractors designed to reduce the amount of boilerplate required to serialize inputs to your handler functions. By simply defining a struct and specifying the data source, these extractors streamline the process of data ingestion & validation through a uniform api.

• The serialized data is accessible through the payload property
• Can be used alongside other parameters and extractors
• Default values can be assigned when defined with the @kwdef macro
• Includes both global and local validators
• Struct definitions can be deeply nested

Supported Extractors:

• Path - extracts from path parameters
• Query - extracts from query parameters,
• Header - extracts from request headers
• Form - extracts form data from the request body
• Body - serializes the entire request body to a given type (String, Float64, etc..)
• ProtoBuffer - extracts the ProtoBuf message from the request body (available through a package extension)
• Json - extracts json from the request body
• JsonFragment - extracts a "fragment" of the json body using the parameter name to identify and extract the corresponding top-level key

Using Extractors & Parameters

In this example we show that the Path extractor can be used alongside regular path parameters. This Also works with regular query parameters and the Query extractor.

struct Add
    b::Int
    c::Int
end

@get "/add/{a}/{b}/{c}" function(req, a::Int, pathparams::Path{Add})
    add = pathparams.payload # access the serialized payload
    return a + add.b + add.c
end

Default Values

Default values can be setup with structs using the @kwdef macro.

@kwdef struct Pet
    name::String
    age::Int = 10
end

@post "/pet" function(req, params::Json{Pet})
    return params.payload # access the serialized payload
end

Validation

On top of serializing incoming data, you can also define your own validation rules by using the validate function. In the example below we show how to use both global and local validators in your code.

• Validators are completely optional
• During the validation phase, Kitten will call the global validator before running a local validator.

import Kitten: validate

struct Person
    name::String
    age::Int
end

# Define a global validator
validate(p::Person) = p.age >= 0

# Only the global validator is ran here
@post "/person" function(req, newperson::Json{Person})
    return newperson.payload
end

# In this case, both global and local validators are ran (this also makes sure the person is age 21+)
# You can also use this sytnax instead: Json(Person, p -> p.age >= 21)
@post "/adult" function(req, newperson = Json{Person}(p -> p.age >= 21))
    return newperson.payload
end

Interpolating variables into endpoints

You can interpolate variables directly into the paths, which makes dynamically registering routes a breeze

(Thanks to @anandijain for the idea)

using Kitten

operations = Dict("add" => +, "multiply" => *)
for (pathname, operator) in operations
    @get "/$pathname/{a}/{b}" function (req, a::Float64, b::Float64)
        return operator(a, b)
    end
end

# start the web server
serve()

Routers

The router() function is an HOF (higher order function) that allows you to reuse the same path prefix & properties across multiple endpoints. This is helpful when your api starts to grow and you want to keep your path operations organized.

Below are the arguments the router() function can take:

router(prefix::String; tags::Vector, middleware::Vector, interval::Real, cron::String)

• tags - are used to organize endpoints in the autogenerated docs
• middleware - is used to setup router & route-specific middleware
• interval - is used to support repeat actions (calling a request handler on a set interval in seconds)
• cron - is used to specify a cron expression that determines when to call the request handler.

using Kitten

# Any routes that use this router will be automatically grouped
# under the 'math' tag in the autogenerated documenation
math = router("/math", tags=["math"])

# You can also assign route specific tags
@get math("/multiply/{a}/{b}", tags=["multiplication"]) function(req, a::Float64, b::Float64)
    return a * b
end

@get math("/divide/{a}/{b}") function(req, a::Float64, b::Float64)
    return a / b
end

serve()

Cron Scheduling

Kitten comes with a built-in cron scheduling system that allows you to call endpoints and functions automatically when the cron expression matches the current time.

When a job is scheduled, a new task is created and runs in the background. Each task uses its given cron expression and the current time to determine how long it needs to sleep before it can execute.

The cron parser in Kitten is based on the same specifications as the one used in Spring. You can find more information about this on the Spring Cron Expressions page.

Cron Expression Syntax

The following is a breakdown of what each parameter in our cron expression represents. While our specification closely resembles the one defined by Spring, it's not an exact 1-to-1 match.

The string has six single space-separated time and date fields:

 ┌───────────── second (0-59)
 │ ┌───────────── minute (0 - 59)
 │ │ ┌───────────── hour (0 - 23)
 │ │ │ ┌───────────── day of the month (1 - 31)
 │ │ │ │ ┌───────────── month (1 - 12) (or JAN-DEC)
 │ │ │ │ │ ┌───────────── day of the week (1 - 7)
 │ │ │ │ │ │          (Monday is 1, Tue is 2... and Sunday is 7)
 │ │ │ │ │ │
 * * * * * *

Partial expressions are also supported, which means that subsequent expressions can be left out (they are defaulted to '*').

# In this example we see only the `seconds` part of the expression is defined.
# This means that all following expressions are automatically defaulted to '*' expressions
@cron "*/2" function()
    println("runs every 2 seconds")
end

Scheduling Endpoints

The router() function has a keyword argument called cron, which accepts a cron expression that determines when an endpoint is called. Just like the other keyword arguments, it can be reused by endpoints that share routers or be overridden by inherited endpoints.

# execute at 8, 9 and 10 o'clock of every day.
@get router("/cron-example", cron="0 0 8-10 * * *") function(req)
    println("here")
end

# execute this endpoint every 5 seconds (whenever current_seconds % 5 == 0)
every5 = router("/cron", cron="*/5")

# this endpoint inherits the cron expression
@get every5("/first") function(req)
    println("first")
end

# Now this endpoint executes every 2 seconds ( whenever current_seconds % 2 == 0 ) instead of every 5
@get every5("/second", cron="*/2") function(req)
    println("second")
end

Scheduling Functions

In addition to scheduling endpoints, you can also use the new @cron macro to schedule functions. This is useful if you want to run code at specific times without making it visible or callable in the API.

@cron "*/2" function()
    println("runs every 2 seconds")
end

@cron "0 0/30 8-10 * * *" function()
  println("runs at 8:00, 8:30, 9:00, 9:30, 10:00 and 10:30 every day")
end

Starting & Stopping Cron Jobs

When you run serve() or serveparallel(), all registered cron jobs are automatically started. If the server is stopped or killed, all running jobs will also be terminated. You can stop the server and all repeat tasks and cron jobs by calling the terminate() function or manually killing the server with ctrl+C.

In addition, Kitten provides utility functions to manually start and stop cron jobs: startcronjobs() and stopcronjobs(). These functions can be used outside of a web server as well.

Repeat Tasks

Repeat tasks provide a simple api to run a function on a set interval.

There are two ways to register repeat tasks:

• Through the interval parameter in a router()
• Using the @repeat macro

It's important to note that request handlers that use this property can't define additional function parameters outside of the default HTTP.Request parameter.

In the example below, the /repeat/hello endpoint is called every 0.5 seconds and "hello" is printed to the console each time.

The router() function has an interval parameter which is used to call a request handler on a set interval (in seconds).

using Kitten

taskrouter = router("/repeat", interval=0.5, tags=["repeat"])

@get taskrouter("/hello") function()
    println("hello")
end

# you can override properties by setting route specific values
@get taskrouter("/bonjour", interval=1.5) function()
    println("bonjour")
end

serve()

Below is an example of how to register a repeat task outside of the router

@repeat 1.5 function()
    println("runs every 1.5 seconds")
end

# you can also "name" a repeat task
@repeat 5 "every-five" function()
    println("runs every 5 seconds")
end

When the server is ran, all tasks are started automatically. But the module also provides utilities to have more fine-grained control over the running tasks using the following functions: starttasks(), stoptasks(), and cleartasks()

Multiple Instances

In some advanced scenarios, you might need to spin up multiple web severs within the same module on different ports. Kitten provides both a static and dynamic way to create multiple instances of a web server.

As a general rule of thumb, if you know how many instances you need ahead of time it's best to go with the static approach.

Static: multiple instance's with @oxidise

Kitten provides a new macro which makes it possible to setup and run multiple instances. It generates methods and binds them to a new internal state for the current module.

In the example below, two simple servers are defined within modules A and B and are started in the parent module. Both modules contain all of the functions exported from Kitten which can be called directly as shown below.

module A
    using Kitten; @oxidise

    get("/") do
        text("server A")
    end
end

module B
    using Kitten; @oxidise

    get("/") do
        text("server B")
    end
end

try
    # start both instances
    A.serve(port=8001, async=true)
    B.serve(port=8002, async=false)
finally
    # shut down if we `Ctrl+C`
    A.terminate()
    B.terminate()
end

Dynamic: multiple instance's with instance()

The instance function helps you create a completely independent instance of an Kitten web server at runtime. It works by dynamically creating a julia module at runtime and loading the Kitten code within it.

All of the same methods from Kitten are available under the named instance. In the example below we can use the get, and serve by simply using dot syntax on the app1 variable to access the underlying methods.

using Kitten

######### Setup the first app #########

app1 = instance()

app1.get("/") do
    text("server A")
end

######### Setup the second app #########

app2 = instance()

app2.get("/") do
    text("server B")
end

######### Start both instances #########

try
    # start both servers together
    app1.serve(port=8001, async=true)
    app2.serve(port=8002)
finally
    # clean it up
    app1.terminate()
    app2.terminate()
end

Multithreading & Parallelism

For scenarios where you need to handle higher amounts of traffic, you can run Kitten in a multithreaded mode. In order to utilize this mode, julia must have more than 1 thread to work with. You can start a julia session with 4 threads using the command below

julia --threads 4

serveparallel() Starts the webserver in streaming mode and handles requests in a cooperative multitasking approach. This function uses Threads.@spawn to schedule a new task on any available thread. Meanwhile, @async is used inside this task when calling each request handler. This allows the task to yield during I/O operations.

using Kitten
using StructTypes
using Base.Threads

# Make the Atomic struct serializable
StructTypes.StructType(::Type{Atomic{Int64}}) = StructTypes.Struct()

x = Atomic{Int64}(0);

@get "/show" function()
    return x
end

@get "/increment" function()
    atomic_add!(x, 1)
    return x
end

# start the web server in parallel mode
serveparallel()

Protocol Buffers

Kitten includes an extension for the ProtoBuf.jl package. This extension provides a protobuf() function, simplifying the process of working with Protocol Buffers in the context of web server. For a better understanding of this package, please refer to its official documentation.

This function has overloads for the following scenarios:

• Decoding a protobuf message from the body of an HTTP request.
• Encoding a protobuf message into the body of an HTTP request.
• Encoding a protobuf message into the body of an HTTP response.

using HTTP
using ProtoBuf
using Kitten

# The generated classes need to be created ahead of time (check the protobufs)
include("people_pb.jl");
using .people_pb: People, Person

# Decode a Protocol Buffer Message
@post "/count" function(req::HTTP.Request)
    # decode the request body into a People object
    message = protobuf(req, People)
    # count the number of Person objects
    return length(message.people)
end

# Encode & Return Protocol Buffer message
@get "/get" function()
    message = People([
        Person("John Doe", 20),
        Person("Alice", 30),
        Person("Bob", 35)
    ])
    # seralize the object inside the body of a HTTP.Response
    return protobuf(message)
end

The following is an example of a schema that was used to create the necessary Julia bindings. These bindings allow for the encoding and decoding of messages in the above example.

syntax = "proto3";
message Person {
    string name = 1;
    sint32 age = 2;
}
message People {
    repeated Person people = 1;
}

Plotting

Kitten is equipped with several package extensions that enhance its plotting capabilities. These extensions make it easy to return plots directly from request handlers. All operations are performed in-memory using an IOBuffer and return a HTTP.Response

Supported Packages and their helper utils:

• CairoMakie.jl: png, svg, pdf, html
• WGLMakie.jl: html
• Bonito.jl: html

CairoMakie.jl

using CairoMakie: heatmap
using Kitten

@get "/cairo" function()
    fig, ax, pl = heatmap(rand(50, 50))
    png(fig)
end

serve()

WGLMakie.jl

using Bonito
using WGLMakie: heatmap
using Kitten
using Kitten: html # Bonito also exports html

@get "/wgl" function()
    fig = heatmap(rand(50, 50))
    html(fig)
end

serve()

Bonito.jl

using Bonito
using WGLMakie: heatmap
using Kitten
using Kitten: html # Bonito also exports html

@get "/bonito" function()
    app = App() do
        return DOM.div(
            DOM.h1("Random 50x50 Heatmap"),
            DOM.div(heatmap(rand(50, 50)))
        )
    end
    return html(app)
end

serve()

Templating

Rather than building an internal engine for templating or adding additional dependencies, Kitten provides two package extensions to support Mustache.jl and OteraEngine.jl templates.

Kitten provides a simple wrapper api around both packages that makes it easy to render templates from strings, templates, and files. This wrapper api returns a render function which accepts a dictionary of inputs to fill out the template.

In all scenarios, the rendered template is returned inside a HTTP.Response object ready to get served by the api. By default, the mime types are auto-detected either by looking at the content of the template or the extension name on the file. If you know the mime type you can pass it directly through the mime_type keyword argument to skip the detection process.

Mustache Templating

Please take a look at the Mustache.jl documentation to learn the full capabilities of the package

Example 1: Rendering a Mustache Template from a File

using Mustache
using Kitten

# Load the Mustache template from a file and create a render function
render = mustache("./templates/greeting.txt", from_file=false)

@get "/mustache/file" function()
    data = Dict("name" => "Chris")
    return render(data)  # This will return an HTML.Response with the rendered template
end

Example 2: Specifying MIME Type for a plain string Mustache Template

using Mustache
using Kitten

# Define a Mustache template (both plain strings and mustache templates are supported)
template_str = "Hello, {{name}}!"

# Create a render function, specifying the MIME type as text/plain
render = mustache(template_str, mime_type="text/plain") # mime_type keyword arg is optional

@get "/plain/text" function()
    data = Dict("name" => "Chris")
    return render(data)  # This will return a plain text response with the rendered template
end

Otera Templating

Please take a look at the OteraEngine.jl documentation to learn the full capabilities of the package

Example 1: Rendering an Otera Template with Logic and Loops

using OteraEngine
using Kitten

# Define an Otera template
template_str = """
<html>
    <head><title>{{ title }}</title></head>
    <body>
        {% for name in names %}
        Hello {{ name }}<br>
        {% end %}
    </body>
</html>
"""

# Create a render function for the Otera template
render = otera(template_str)

@get "/otera/loop" function()
    data = Dict("title" => "Greetings", "names" => ["Alice", "Bob", "Chris"])
    return render(data)  # This will return an HTML.Response with the rendered template
end

In this example, an Otera template is defined with a for-loop that iterates over a list of names, greeting each name.

Example 2: Running Julia Code in Otera Template

using OteraEngine
using Kitten

# Define an Otera template with embedded Julia code
template_str = """
The square of {{ number }} is {< number^2 >}.
"""

# Create a render function for the Otera template
render = otera(template_str)

@get "/otera/square" function()
    data = Dict("number" => 5)
    return render(data)  # This will return an HTML.Response with the rendered template
end

In this example, an Otera template is defined with embedded Julia code that calculates the square of a given number.

Mounting Static Files

You can mount static files using this handy function which recursively searches a folder for files and mounts everything. All files are loaded into memory on startup.

using Kitten

# mount all files inside the "content" folder under the "/static" path
staticfiles("content", "static")

# start the web server
serve()

Mounting Dynamic Files

Similar to staticfiles, this function mounts each path and re-reads the file for each request. This means that any changes to the files after the server has started will be displayed.

using Kitten

# mount all files inside the "content" folder under the "/dynamic" path
dynamicfiles("content", "dynamic")

# start the web server
serve()

Performance Tips

Disabling the internal logger can provide some massive performance gains, which can be helpful in some scenarios. Anecdotally, i've seen a 2-3x speedup in serve() and a 4-5x speedup in serveparallel() performance.

# This is how you disable internal logging in both modes
serve(access_log=nothing)
serveparallel(access_log=nothing)

Logging

Kitten provides a default logging format but allows you to customize the format using the access_log parameter. This functionality is available in both the serve() and serveparallel() functions.

You can read more about the logging options here

# Uses the default logging format
serve()

# Customize the logging format
serve(access_log=logfmt"[$time_iso8601] \"$request\" $status")

# Disable internal request logging
serve(access_log=nothing)

Middleware

Middleware functions make it easy to create custom workflows to intercept all incoming requests and outgoing responses. They are executed in the same order they are passed in (from left to right).

They can be set at the application, router, and route layer with the middleware keyword argument. All middleware is additive and any middleware defined in these layers will be combined and executed.

Middleware will always be executed in the following order:

application -> router -> route

Now lets see some middleware in action:

using Kitten
using HTTP

const CORS_HEADERS = [
    "Access-Control-Allow-Origin" => "*",
    "Access-Control-Allow-Headers" => "*",
    "Access-Control-Allow-Methods" => "POST, GET, OPTIONS"
]

# https://juliaweb.github.io/HTTP.jl/stable/examples/#Cors-Server
function CorsMiddleware(handler)
    return function(req::HTTP.Request)
        println("CORS middleware")
        # determine if this is a pre-flight request from the browser
        if HTTP.method(req)=="OPTIONS"
            return HTTP.Response(200, CORS_HEADERS)
        else
            return handler(req) # passes the request to the AuthMiddleware
        end
    end
end

function AuthMiddleware(handler)
    return function(req::HTTP.Request)
        println("Auth middleware")
        # ** NOT an actual security check ** #
        if !HTTP.headercontains(req, "Authorization", "true")
            return HTTP.Response(403)
        else
            return handler(req) # passes the request to your application
        end
    end
end

function middleware1(handle)
    function(req)
        println("middleware1")
        handle(req)
    end
end

function middleware2(handle)
    function(req)
        println("middleware2")
        handle(req)
    end
end

# set middleware at the router level
math = router("math", middleware=[middleware1])

# set middleware at the route level
@get math("/divide/{a}/{b}", middleware=[middleware2]) function(req, a::Float64, b::Float64)
    return a / b
end

# set application level middleware
serve(middleware=[CorsMiddleware, AuthMiddleware])

Custom Response Serializers

If you don't want to use Kitten's default response serializer, you can turn it off and add your own! Just create your own special middleware function to serialize the response and add it at the end of your own middleware chain.

Both serve() and serveparallel() have a serialize keyword argument which can toggle off the default serializer.

using Kitten
using HTTP
using JSON3

@get "/divide/{a}/{b}" function(req::HTTP.Request, a::Float64, b::Float64)
    return a / b
end

# This is just a regular middleware function
function myserializer(handle)
    function(req)
        try
          response = handle(req)
          # convert all responses to JSON
          return HTTP.Response(200, [], body=JSON3.write(response))
        catch error
            @error "ERROR: " exception=(error, catch_backtrace())
            return HTTP.Response(500, "The Server encountered a problem")
        end
    end
end

# make sure 'myserializer' is the last middleware function in this list
serve(middleware=[myserializer], serialize=false)

Autogenerated Docs with Swagger

Swagger documentation is automatically generated for each route you register in your application. Only the route name, parameter types, and 200 & 500 responses are automatically created for you by default.

You can view your generated documentation at /docs, and the schema can be found under /docs/schema. Both of these values can be changed to whatever you want using the configdocs() function. You can also opt out of autogenerated docs entirely by calling the disabledocs() function before starting your application.

To add additional details you can either use the built-in mergeschema() or setschema() functions to directly modify the schema yourself or merge the generated schema from the SwaggerMarkdown.jl package (I'd recommend the latter)

Below is an example of how to merge the schema generated from the SwaggerMarkdown.jl package.

using Kitten
using SwaggerMarkdown

# Here's an example of how you can merge autogenerated docs from SwaggerMarkdown.jl into your api
@swagger """
/divide/{a}/{b}:
  get:
    description: Return the result of a / b
    parameters:
      - name: a
        in: path
        required: true
        description: this is the value of the numerator
        schema:
          type : number
    responses:
      '200':
        description: Successfully returned an number.
"""
@get "/divide/{a}/{b}" function (req, a::Float64, b::Float64)
    return a / b
end

# title and version are required
info = Dict("title" => "My Demo Api", "version" => "1.0.0")
openApi = OpenAPI("3.0", info)
swagger_document = build(openApi)

# merge the SwaggerMarkdown schema with the internal schema
mergeschema(swagger_document)

# start the web server
serve()

Below is an example of how to manually modify the schema

using Kitten
using SwaggerMarkdown

# Only the basic information is parsed from this route when generating docs
@get "/multiply/{a}/{b}" function (req, a::Float64, b::Float64)
    return a * b
end

# Here's an example of how to update a part of the schema yourself
mergeschema("/multiply/{a}/{b}",
  Dict(
    "get" => Dict(
      "description" => "return the result of a * b"
    )
  )
)

# Here's another example of how to update a part of the schema yourself, but this way allows you to modify other properties defined at the root of the schema (title, summary, etc.)
mergeschema(
  Dict(
    "paths" => Dict(
      "/multiply/{a}/{b}" => Dict(
        "get" => Dict(
          "description" => "return the result of a * b"
        )
      )
    )
  )
)

API Reference (macros)

@get, @post, @put, @patch, @delete

  @get(path, func)

Parameter	Type	Description
path	string or router()	Required. The route to register
func	function	Required. The request handler for this route

Used to register a function to a specific endpoint to handle that corresponding type of request

@route

  @route(methods, path, func)

Parameter	Type	Description
methods	array	Required. The types of HTTP requests to register to this route
path	string or router()	Required. The route to register
func	function	Required. The request handler for this route

Low-level macro that allows a route to be handle multiple request types

staticfiles

  staticfiles(folder, mount)

Parameter	Type	Description
folder	string	Required. The folder to serve files from
mountdir	string	The root endpoint to mount files under (default is "static")
set_headers	function	Customize the http response headers when returning these files
loadfile	function	Customize behavior when loading files

Serve all static files within a folder. This function recursively searches a directory and mounts all files under the mount directory using their relative paths.

dynamicfiles

  dynamicfiles(folder, mount)

Parameter	Type	Description
folder	string	Required. The folder to serve files from
mountdir	string	The root endpoint to mount files under (default is "static")
set_headers	function	Customize the http response headers when returning these files
loadfile	function	Customize behavior when loading files

Serve all static files within a folder. This function recursively searches a directory and mounts all files under the mount directory using their relative paths. The file is loaded on each request, potentially picking up any file changes.

Request helper functions

html()

  html(content, status, headers)

Parameter	Type	Description
content	string	Required. The string to be returned as HTML
status	integer	The HTTP response code (default is 200)
headers	dict	The headers for the HTTP response (default has content-type header set to "text/html; charset=utf-8")

Helper function to designate when content should be returned as HTML

queryparams()

  queryparams(request)

Parameter	Type	Description
req	HTTP.Request	Required. The HTTP request object

Returns the query parameters from a request as a Dict()

Body Functions

text()

  text(request)

Parameter	Type	Description
req	HTTP.Request	Required. The HTTP request object

Returns the body of a request as a string

binary()

  binary(request)

Parameter	Type	Description
req	HTTP.Request	Required. The HTTP request object

Returns the body of a request as a binary file (returns a vector of UInt8s)

json()

  json(request, classtype)

Parameter	Type	Description
req	HTTP.Request	Required. The HTTP request object
classtype	struct	A struct to deserialize a JSON object into

Deserialize the body of a request into a julia struct

License

MIT License, see LICENSE.md for more information.

Migrated from Oxygen.jl and modified to work with JuliaKit project.