快速用 Haskell 构建超级简单的 Web 技术栈！
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-
会话，用户可以刷新页面，或者关闭页面后再打开，但在打开之后应该看到相同的内容。 -
持久化和数据库访问，我们需要将每个用户的定时器和笔记保存下来。 另一个需求是定时器需要维持剩余的时间（用户设置了一个30分钟的定时器，然后不小心关闭了页面，应该如何？ ） -
运行时的配置，因为我们不能把数据库连接的信息硬编码到代码里。 -
日志。 日志对于Web应用的作用不言而喻。
{-# LANGUAGE OverloadedStrings #-}
import Web.Spock
as Spock
import Web.Spock.Config
as Spock
import Data.Aeson
as A
main :: IO ()
main =
do
spockCfg <- defaultSpockCfg () PCNoDatabase ()
runSpock
3000 $ spock spockCfg $
do
get root $
do
Spock.html
"<div>Hello world!</div>"
get
"users" $
do
Spock.json (A.
object [
"users" .= users ])
get (
"users" <
//> var <//> "friends") $ \userID -> do
Spock.json (A.
object [
"userID" .= (userID ::
Int),
"friends" .= A.Null ])
where users :: [String]
users = [
"bob",
"alice"]
数据库访问：postgresql-simple
postgresql-simple基本上只允许您对数据库运行原始SQL查询，而没有多余的装饰，例如防止注入攻击。它可以实现您的期望，仅此而已。
{-# LANGUAGE OverloadedStrings #-}
import Database.PostgreSQL.Simple
userLoginsQuery :: Query
userLoginsQuery =
"SELECT l.user_id, COUNT(1) FROM logins l GROUP BY l.user_id;"
getUserLogins :: Connection -> IO [(
Int,
Int)]
getUserLogins conn = query_ conn userLoginsQuery
{-
# LANGUAGE OverloadedStrings #-}
import Database.PostgreSQL.Simple
userLoginsQuery :: Query
userLoginsQuery =
"SELECT l.user_id, COUNT(1) FROM logins l GROUP BY l.user_id;"
getUserLogins :: Connection -> IO [(Int, Int)]
getUserLogins conn = query_ conn userLoginsQuery
# An example config file.
app_name =
"The Whispering Fog"
db {
pool {
stripes =
4
resource_ttl =
300
}
username =
"pallas"
password =
"thefalloflatinium"
dbname =
"italy"
}
{-
# LANGUAGE OverloadedStrings #-}
import Data.Configurator
as Cfg
import Database.PostgreSQL.Simple
data MyAppConfig = MyAppConfig
{ appName :: String
, appDBConnection :: Connection
}
getAppConfig :: IO MyAppConfig
getAppConfig =
do
cfgFile <- Cfg.load [
"app-configuration.cfg"]
name <- Cfg.
require cfgFile
"app_name"
conn <-
do
username <- Cfg.
require cfgFile
"db.username"
password <- Cfg.
require cfgFile
"db.password"
dbname <- Cfg.
require cfgFile
"db.dbname"
connect $ defaultConnectInfo
{ connectUser = username
, connectPassword = password
, connectDatabase = dbname
}
pure $ MyAppConfig
{ appName = name
, appDBConnection = conn
}
import System.
Log.FastLogger as
Log
logMsg ::
Log.LoggerSet ->
String -> IO ()
logMsg logSet msg =
Log.pushLogStrLn logSet (
Log.toLogStr msg)
doSomething :: IO ()
doSomething =
do
logSet <-
Log.newStderrLoggerSet
Log.defaultBufSize
logMsg logSet
"message 1"
logMsg logSet
"message 2"
{-
# LANGUAGE OverloadedStrings #-}
import Data.ByteString.Lazy
import Text.Blaze.Html5
as HTML
import Text.Blaze.Html5.Attributes
as HTML hiding ( title )
import Text.Blaze.Html.Renderer.Utf8
as HTML
dashboardHTML :: HTML.Html
dashboardHTML = HTML.html $
HTML.docTypeHtml $
do
HTML.head $
do
HTML.title
"Timers and Notes"
HTML.meta ! HTML.charset
"utf-8"
HTML.script ! HTML.src
"/js/bundle.js" $
""
HTML.body $
do
HTML.div ! HTML.id
"content" $
""
dashboardBytes :: ByteString
dashboardBytes = HTML.renderHtml dashboardHTML
【End】
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