[英]How to Create Asynchronous HttpWebRequest in Silverlight( F#)
正如我所提到的,因為Silverlight HttpWebRequest.Create在異步塊內部掛起 ,我只是創建了一組回調函數來實現相同的異步塊。
登錄過程需要兩個步驟:
1)獲取返回cookie的頁面的請求2)表單發布到第二頁,通過該cookie並執行身份驗證
以下是src。 無論是關於異步HttpWebRequest還是關於F#代碼樣式,歡迎和贊賞任何建議和討論。
module File1
open System
open System.IO
open System.Net
open System.Text
open System.Security
open System.Runtime.Serialization
open System.Collections.Generic
open JsonData
open System.Net.Browser
open System.Threading
module rpc =
let mutable BASE_DNS = ""
let mutable requestId : int = 0
let getId() =
requestId <- requestId + 1
requestId.ToString()
module internal Helper =
///<Summary>
///Transfer data from Security.loginToRpc to Helper.FetchCookieCallback
///</Summary>
type LoginRequestRecord = {
Request : HttpWebRequest;
UserName : string;
Password : string;
AuthenticationUrl : string;
CallbackUI : (bool -> unit)
}
///<Summary>
///Transfer data from Helper.FetchCookieCallback to Helper.requestAuthenticationCallback
///</Summary>
type AuthenticationRecord = {
Request : HttpWebRequest;
UserName : string;
Password : string;
CallbackUI : (bool -> unit)
}
///<Summary>
///Transfer data from Helper.requestAuthenticationCallback to Helper.responseAuthenticationCallback
///</Summary>
type ResponseAuthenticationRecord = {
Request : HttpWebRequest;
CallbackUI : (bool -> unit)
}
///<Summary>
///The cookieContainer for all the requests in the session
///</Summary>
let mutable cookieJar = new CookieContainer()
///<summary>
///Function: Create HttpRequest
///Param: string
///Return: HttpWebRequest
///</summary>
let internal createHttpRequest (queryUrl : string) =
let uri = new Uri(queryUrl)
let request : HttpWebRequest =
downcast WebRequestCreator.ClientHttp.Create(
new Uri(queryUrl, UriKind.Absolute))
request
///<summary>
///Function: set request whose method is "GET".
///Attention: no contentType for "GET" request~!!!!!!!!!!!!!!!!
///Param: HttpWebRequest
///Return: unit
///</summary>
let internal requestGetSet (request : HttpWebRequest) =
request.Method <- "GET"
///<summary>
///Function: set request whose method is "POST" and its contentType
///Param: HttpWebRequest and contentType string
///Return: unit
///</summary>
let internal requestPostSet (request : HttpWebRequest) contentType =
request.Method <- "POST"
request.ContentType <- contentType
///<summary>
///Function: Callback function inluding EndGetResponse method of request
///Param: IAsyncResult includes the information of HttpWebRequest
///Return: unit
///</summary>
let internal responseAuthenticationCallback (ar : IAsyncResult) =
let responseAuthentication : ResponseAuthenticationRecord
= downcast ar.AsyncState
try
let response = responseAuthentication.Request.EndGetResponse(ar)
//check whether the authentication is successful,
//which may be changed later into other methods
match response.ContentLength with
| -1L -> responseAuthentication.CallbackUI true
| _ -> responseAuthentication.CallbackUI false
()
with
| Ex -> responseAuthentication.CallbackUI false
///<summary>
///Function: Callback function for user to log into the website
///Param: IAsyncResult includes the information of
///HttpWebRequest and user's identity
///Return: unit
///</summary>
let internal requestAuthenticationCallback (ar : IAsyncResult) =
let authentication : AuthenticationRecord = downcast ar.AsyncState
try
let requestStream = authentication.Request.EndGetRequestStream(ar)
let streamWriter = new StreamWriter(requestStream)
streamWriter.Write(
String.Format(
"j_username={0}&j_password={1}&login={2}",
authentication.UserName,
authentication.Password,
"Login"))
streamWriter.Close()
let responseAuthentication = {
ResponseAuthenticationRecord.Request = authentication.Request
ResponseAuthenticationRecord.CallbackUI = authentication.CallbackUI
}
authentication.Request.BeginGetResponse(
new AsyncCallback(responseAuthenticationCallback),
responseAuthentication)
|> ignore
with
| Ex -> authentication.CallbackUI false
()
///<summary>
///This is a magic number to check
///whether the first request have got the cookie from the server-side,
///which should be changed later
///</summary>
let countHeadersAfterGetCookie = 8
///<summary>
///Function: Callback function to get the cookie and
///Param: IAsyncResult includes the information of
///login request, username, password and callbackUI
///Return:
///</summary>
let internal FetchCookieCallback (ar : IAsyncResult) =
let loginRequest : LoginRequestRecord = downcast ar.AsyncState
try
let response = loginRequest.Request.EndGetResponse(ar)
let request : HttpWebRequest
= createHttpRequest loginRequest.AuthenticationUrl
requestPostSet request "application/x-www-form-urlencoded"
request.CookieContainer <- cookieJar
//if the cookie is got, call the callback function; or else, return to UI
match response.Headers.Count with
| countHeadersAfterGetCookie ->
let authentication = {
AuthenticationRecord.Request = request;
AuthenticationRecord.UserName = loginRequest.UserName;
AuthenticationRecord.Password = loginRequest.Password;
AuthenticationRecord.CallbackUI = loginRequest.CallbackUI
}
request.BeginGetRequestStream(
new AsyncCallback(requestAuthenticationCallback),
authentication)
|> ignore
()
| _ ->
loginRequest.CallbackUI false
()
with
| Ex -> loginRequest.CallbackUI false
module Security =
///<summary>
///Function: Use the async workflow around 2 we calls:
/// 1. get the cookie; 2. log into the website
///Param: UserName and password
///Return: unit
///</summary>
let loginToRpc (userName : string)
(password : string)
(callbackUI : (bool-> unit)) =
let sessionIdUrl = BASE_DNS
let authenticationUrl = BASE_DNS + "..................."
let request : HttpWebRequest = Helper.createHttpRequest sessionIdUrl
Helper.requestGetSet(request)
request.CookieContainer <- Helper.cookieJar
let loginRequest = {
Helper.LoginRequestRecord.Request = request
Helper.LoginRequestRecord.UserName = userName
Helper.LoginRequestRecord.Password = password
Helper.LoginRequestRecord.AuthenticationUrl = authenticationUrl
Helper.LoginRequestRecord.CallbackUI = callbackUI
}
request.BeginGetResponse(new
AsyncCallback(Helper.FetchCookieCallback),
loginRequest)
|> ignore
()
通常在創建記錄實例時,不需要像您一樣對每個屬性進行完全限定。
let authentication = {
AuthenticationRecord.Request = request;
AuthenticationRecord.UserName = loginRequest.UserName;
AuthenticationRecord.Password = loginRequest.Password;
AuthenticationRecord.CallbackUI = loginRequest.CallbackUI
}
只要您使用的屬性的名稱和類型僅匹配一種記錄類型,F#通常足夠聰明,可以弄清楚您的意思。
let authentication = {
Request = request;
UserName = loginRequest.UserName;
Password = loginRequest.Password;
CallbackUI = loginRequest.CallbackUI
}
另外,我可能傾向於在String.Format
上使用sprintf
:
String.Format(
"j_username={0}&j_password={1}&login={2}",
authentication.UserName,
authentication.Password,
"Login"))
sprintf "j_username=%s&j_password=%s&login=%s"
authentication.UserName authentication.Password "Login"
但是由於生成的字符串被傳遞給StreamWriter
,后者繼承自TextWriter
另一個選項是使用fprintf
直接寫入TextWriter
。
fprintf streamWriter "j_username=%s&j_password=%s&login=%s"
authentication.UserName authentication.Password "Login"
我通常將本地狀態保持在本地狀態,將其隱藏在封閉內。 所以,除非我錯過了對requestId
的引用,否則我會將它移到getId
:
let mutable requestId : int = 0
let getId() =
requestId <- requestId + 1
requestId.ToString()
// changes to:
let getId =
let mutable requestId : int = 0
(fun () ->
requestId <- requestId + 1
requestId.ToString())
在第二個版本中, getId
實際上是底部的fun
,在let mutable...
之后。 fun
捕獲requestId
,然后給出名稱getId
。 由於requestId
超出了范圍,因此沒有其他人可以更改甚至看到它。
我回答原始的“Silverlight HttpWebRequest.Create掛在異步塊內”, 檢查一下 ......
在您的情況下,您當然需要身份驗證,但此request.ContentType <- contentType
可能會導致一些問題。
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