What is Saturn ?

Saturn is a web development framework written in F# which implements the server-side MVC pattern.

https://saturnframework.org/explanations/overview.html https://saturnframework.org/

Why Saturn? 🧐

• SAFE official recommend 👍
• Modern programming model 👍
• High performance 👍
• Developer experience 👍
• Created by Community 👍

Saturn Introduction

Hello world Saturn

open Saturn
open Giraffe

let endpoints =
    router { get "/" (text "Hello World from Saturn") }

let app =
    application {
        url ("https://localhost:5000")
        use_router endpoints
    }

run app

Practice

1. Create F# console project
   • dotnet new console -lang "F#"
2. Add the Saturn NuGet Package
   • dotnet add package Saturn

3. Copy and paste

open Saturn
open Giraffe

let endpoints =
    router { get "/" (text "Hello World from Saturn") }
  //Change the text function in endpoints to either xml or json.
let app =
    application {
        url ("https://localhost:5000")
        use_router endpoints
    }

run app

Saturn Router

let getProductById (productId: int64) =
    let a = (sprintf "Hello my id is %d" productId)
    text a

let routes =
    router {
        get "/" (text "Hello from Saturn!")
        getf "/%d" getProductById
        //post、delete、put、postf...
    }

forward

let publicApi =
    router { get "/" (text "This is publicApi") }

let routes = router { forward "/public" publicApi }

Saturn Controller

Resource

• Path to a function
  • Use router { }
  • Links a function to an endpoint
• Path to an object
  • Use controller { }
  • Provides a set of ready-made endpoints for CRUD behaviour over an object.

controller

let resource = controller {
    index indexAction
    show showAction
    add addAction
    edit editAction
    create createAction
    update updateAction
    patch patchAction
    delete deleteAction
    deleteAll deleteAllAction
}

• index — mapped into GET request at / endpoint. Usually used to render a view displaying list of items, or return whole list of items.
• show — mapped into GET request at /:id endpoint. Usually used to render a view displaying details of particular item, or return single item with given id.
• create — mapped into POST request at / endpoint. Used to create and save new item.

• update — mapped into POST and PUT requests at /:id endpoint. Used to update existing item. Usually replaces original item (keeping id), and requires are fields to be filled in the incoming item.
• delete — mapped into DELETE request at /:id endpoint. Used to delete or deactivate existing item.
• deleteAll — mapped into DELETE request at / endpoint. Used to delete or deactivate all items.

https://medium.com/lambda-factory/magic-of-saturn-controllers-bafbc46d485f

example

let helloEndpoint = controller{
    index (fun ctx -> "Hello" |> Controller.text ctx)
    show (fun ctx id -> (sprintf "Show %i" id)|> Controller.text ctx)
}

Saturn Fundamentals

HTTP Context (ctx)

• Contains all details on the request / response
  • URL
  • Query String
  • Headers
  • Body

HTTP Endpoints as Functions

• Http Request ⏩ Http Response
• HttpContext ⏩ HttpContext

HTTP Handler

For example: text

• Sets the Content Type to text/plain
• Sets the Response Body to the text you provide it
• Sets the Response Code to 202

HTTP handler can be composed

Code snipts

module Fuber.Routes

open Giraffe
open Saturn


type Profile = { Username: string }

let getProfile next ctx =
    let profile = { Username = "JW" }

    json profile next ctx
// next ctx //return this , pipeline will return getProfile2 result

// never run
let getProfile2 next ctx =
    let profile = { Username = "QQ" }

    json profile next ctx

let setMyHeader = setHttpHeader "myCustomHeader" "abcd"


let headerPipe =
    pipeline {
        plug setMyHeader
        plug getProfile
        plug getProfile2 // never run because getProfile get something, if getProfile return None, pipeline will continue.
    }

let apiRouter = router { get "/profile" headerPipe }

let router = router { forward "/api" apiRouter }


let app =
    application {
        url "http://0.0.0.0:8080/"
        use_router router
        memory_cache
        use_static "content"
        use_gzip
    }

run app

Lab

1. Create F# console project
   • dotnet new console -lang "F#"
2. Add the Saturn NuGet Package
   • dotnet add package Saturn

3. Copy & paste

module Fuber.Routes

open Giraffe
open Saturn


type Profile = { Username: string }

let getProfile next ctx =
    let profile = { Username = "JW" }

    json profile next ctx
// next ctx //return this , pipeline will return getProfile2 result

// never run
let getProfile2 next ctx =
    let profile = { Username = "QQ" }

    json profile next ctx

let setMyHeader = setHttpHeader "myCustomHeader" "abcd"


let headerPipe =
    pipeline {
        plug setMyHeader
        plug getProfile
        plug getProfile2 // never run because getProfile get something, if getProfile return None, pipeline will continue.
    }

let apiRouter = router { get "/profile" headerPipe }

let router = router { forward "/api" apiRouter }


let app =
    application {
        url "http://0.0.0.0:8080/"
        use_router router
        memory_cache
        use_static "content"
        use_gzip
    }

run app

4. new a countController to router and prefix is "/v1"
5. new index and show functions in countController, and return Hello 、 Hello id

• GET http://localhost:8080/v1/ return Hello
• GET http://localhost:8080/v1/1 return Hello 1