Haskell Wai Tutorial

1. What is Wai?
2. How to install it?
3. First Hello World Example.
4. How to response a file from your Wai server.
5. Wai and Database.
6. Execute shell command on your Wai server.

1 What is Wai?

Wai is a common protocol for communication between web application and web server.
Wai can be used to create RESTful web services.

2 How to install it?

cabal install wai

3 First Hello World Example.

responseLBS

{-# LANGUAGE OverloadedStrings #-}               
import Network.Wai                               
import Network.HTTP.Types                        
import Network.Wai.Handler.Warp (run)            
app :: Application                               
app _ respond = do                               
    respond $ responseLBS                        
        status200                                
        [("Content-Type", "text/plain")]         
        "Hello, World!"                          

main :: IO ()                                    
main = do                                        
    putStrLn $ "http://localhost:8080/"          
    run 8080 app

4 How to response a file from your Wai server.

responseFile
Assume file index.html is in the current dir where the server is running.

plainIndex::Response
plainIndex = responseFile
    status200
    [("Content-Type", "text/html")]
    "index.html"
    Nothing

app _ respond = do
    respond responseFile
main:: IO()
main = do
      run 8080 app

Haskell Wai Tutorial

Table of Contents

1 What is Wai?

2 How to install it?

3 First Hello World Example.

4 How to response a file from your Wai server.

5 Wai and Database.

6 Execute shell command on your Wai server.