ASP.NET Tutorial/Development/HTTP Handlers — различия между версиями

Текущая версия на 11:56, 26 мая 2010

Содержание

1 Creating a Custom HTTP Handler
2 Creating a Generic Handler
3 Creating HTTP Handlers
4 HelloWorld HttpHandler (VB)
5 Implementing the IHttpHandler Interface
6 Log user in HttpModule
7 RSS Handler
8 Source viewer Http Handler

Creating a Custom HTTP Handler

Create a class that implements the IHttpHandler interface. 
Place this class in the App_Code directory. 
using System;
using System.Web;
namespace HttpExtensions
{
    public class SimpleHandler : IHttpHandler
    {
        public void ProcessRequest(System.Web.HttpContext context)
        {
            HttpResponse response = context.Response;
            response.Write("<html><body><h1>Rendered by the SimpleHandler") ;
            response.Write("</h1></body></html>") ;
        }
        public bool IsReusable
        {
            get {return true;}
        }
    }
}
Configuring a Custom HTTP Handler
<?xml version="1.0"?>
<configuration xmlns="http://schemas.microsoft.ru/.NetConfiguration/v2.0">
  <system.web>
    <httpHandlers>
      <add verb="*" path="source.simple" type="SourceHandler"/>
      <add verb="*" path="test.simple" type="SimpleHandler" />
    </httpHandlers>
  </system.web>
</configuration>

Creating a Generic Handler

When you create a Generic Handler, you create a file that ends with the extension .ashx. Whenever you request the .ashx file, the Generic Handler executes.
A Generic Handler is like an ASP.NET page that contains a single method that renders content to the browser. 
You can"t add any controls declaratively to a Generic Handler. 
A Generic Handler doesn"t support events such as the Page Load or Page PreRender events.
File: ImageTextHandler.ashx
<%@ WebHandler Language="C#" Class="ImageTextHandler" %>
using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
public class ImageTextHandler : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
        string text = context.Request.QueryString["text"];
        string font = context.Request.QueryString["font"];
        string size = context.Request.QueryString["size"];
        Font fntText = new Font(font, float.Parse(size));
        Bitmap bmp = new Bitmap(10, 10);
        Graphics g = Graphics.FromImage(bmp);
        SizeF bmpSize = g.MeasureString(text, fntText);
        int width = (int)Math.Ceiling(bmpSize.Width);
        int height = (int)Math.Ceiling(bmpSize.Height);
        bmp = new Bitmap(bmp, width, height);
        g.Dispose();
        g = Graphics.FromImage(bmp);
        g.Clear(Color.White);
        g.DrawString(text, fntText, Brushes.Black, new PointF(0, 0));
        g.Dispose();
        bmp.Save(context.Response.OutputStream, ImageFormat.Gif);
    }
    public bool IsReusable
    {
        get
        {
            return true;
        }
    }
}
You specify the image that you want to return from the handler by making a request that looks like this:
/ImageTextHandler.ashx?text=Hello&font=Arial&size=30

The IsReusable property indicates whether the same handler can be reused over multiple requests. 
The following page uses the ImageTextHandler.ashx file. 
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show ImageTextHandler</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <img src="ImageTextHandler.ashx?text=Some Text&font=WebDings&size=42" />
    <br />
    <img src="ImageTextHandler.ashx?text=Some Text&font=Comic Sans MS&size=42" />
    <br />
    <img src="ImageTextHandler.ashx?text=Some Text&font=Courier New&size=42" />
    </div>
    </form>
</body>
</html>

Creating HTTP Handlers

An HTTP Handler is a .NET class that executes whenever you make a request for a file at a certain path. 
Each type of resource that you can request from an ASP.NET application has a corresponding handler.
You can create a Generic Handler, or you can implement the IHttpHandler interface.

HelloWorld HttpHandler (VB)

File: HelloWorldHttpHandler.ashx
<%@ WebHandler Language="VB" Class="HelloWorldHandler" %>
imports System
imports System.Web
public Class HelloWorldHandler
    Implements IHttpHandler
    Sub ProcessRequest(context As HttpContext) Implements IHttpHandler.ProcessRequest
        Dim Request As HttpRequest = context.Request
        Dim Response As HttpResponse = context.Response
        Response.Write("<html>")
        Response.Write("<body>")
        Response.Write("   <h1> Hello " + Request.QueryString("Name") + "</h1>")
        Response.Write("</body>")
        Response.Write("</html>")
    End Sub
    Public ReadOnly Property IsReusable As Boolean Implements IHttpHandler.IsReusable
        Get
          return true
        End Get
    End Property
End Class

Implementing the IHttpHandler Interface

File: App_Code\ImageHandler.cs
using System;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using System.Web.Configuration;
namespace MyNamespace
{
    public class ImageHandler : IHttpHandler
    {
        const string connectionStringName = "Images";
        public void ProcessRequest(HttpContext context)
        {
            context.Response.Buffer = false;
            string fileName = VirtualPathUtility.GetFileName(context.Request.Path);
            string conString = WebConfigurationManager.ConnectionStrings [connectionStringName].ConnectionString;
            SqlConnection con = new SqlConnection(conString);
            SqlCommand cmd = new SqlCommand("SELECT Image FROM Images WHERE FileName=@FileName", con);
            cmd.Parameters.AddWithValue("@fileName", fileName);
            using (con)
            {
                con.Open();
                SqlDataReader reader = cmd.ExecuteReader(CommandBehavior. SequentialAccess);
                if (reader.Read())
                {
                    int bufferSize = 8040;
                    byte[] chunk = new byte[bufferSize];
                    long retCount;
                    long startIndex = 0;
                    retCount = reader.GetBytes(0, startIndex, chunk, 0, bufferSize);
                    while (retCount == bufferSize)
                    {
                        context.Response.BinaryWrite(chunk);
                        startIndex += bufferSize;
                        retCount = reader.GetBytes(0, startIndex, chunk, 0, bufferSize);
                    }
                    byte[] actualChunk = new Byte[retCount - 1];
                    Buffer.BlockCopy(chunk, 0, actualChunk, 0, (int)retCount - 1);
                    context.Response.BinaryWrite(actualChunk);
                }
            }
        }
        public bool IsReusable
        {
            get { return true; }
        }
    }
}
            

Register the class in the web configuration file. 
File: Web.Config
<configuration>
  <connectionStrings>
    <add name="Images"
      connectionString="Data Source=.\SQLExpress;Integrated
           Security=True;AttachDBFileName=|DataDirectory|ImagesDB.mdf;
           User Instance=True"/>
  </connectionStrings>
    <system.web>
      <httpHandlers>
        <add path="*.gif" verb="*"
           type="MyNamespace.ImageHandler" validate="false" />
        <add path="*.jpeg" verb="*"
           type="MyNamespace.ImageHandler" validate="false" />
        <add path="*.jpg" verb="*"
           type="MyNamespace.ImageHandler" validate="false" />
      </httpHandlers>
    </system.web>
</configuration>
Displaying images with the ImageHandler.
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    protected void btnAdd_Click(object sender, EventArgs e)
    {
        if (upFile.HasFile)
        {
                srcImages.Insert();
        }
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Image Upload</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Label
        id="lblFile"
        Text="Image File:"
        AssociatedControlID="upFile"
        Runat="server" />
    <asp:FileUpload
        id="upFile"
        Runat="server" />
    <asp:Button
        id="btnAdd"
        Text="Add Image"
        OnClick="btnAdd_Click"
        Runat="server" />
    <hr />
    <asp:GridView
        id="grdImages"        
        DataSourceID="srcImages"
        AutoGenerateColumns="false"
        ShowHeader="false"
        GridLines="None"
        Runat="server">
        <Columns>
        <asp:ImageField
            DataImageUrlField="FileName"
            DataAlternateTextField="FileName" />
        </Columns>
    </asp:GridView>
    <asp:SqlDataSource
        id="srcImages"
        ConnectionString="<%$ ConnectionStrings:Images %>"
        SelectCommand="SELECT FileName FROM Images"
        InsertCommand="INSERT Images (FileName,Image) VALUES (@FileName,@FileBytes)"
        Runat="server">
        <InsertParameters>
            <asp:ControlParameter Name="FileName" ControlID="upFile" PropertyName="FileName" />
            <asp:ControlParameter Name="FileBytes" ControlID="upFile" PropertyName="FileBytes" />
        </InsertParameters>
    </asp:SqlDataSource>
    </div>
    </form>
</body>
</html>

Log user in HttpModule

using System;
using System.Web;
using System.Diagnostics;

public class LogUserModule : IHttpModule
{
  public void Init(HttpApplication httpApp)
  {
    httpApp.AuthenticateRequest += new EventHandler(OnAuthentication);
  }
  private void OnAuthentication(object sender, EventArgs a)
  {
    string name = HttpContext.Current.User.Identity.Name;
    EventLog log = new EventLog();
    log.Source = "Log User Module";
    log.WriteEntry(name + " was authenticated.");
  }
  public void Dispose(){ }
}

RSS Handler

File: App_Code\RSSHandler.cs

using System;
using System.Web;
using System.Net;
using System.IO;
namespace MyNamespace
{
    public class RSSHandler : IHttpAsyncHandler
    {
        private HttpContext _context;
        private WebRequest _request;
        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {
            _context = context;
            _request = WebRequest.Create ("http://msdn.microsoft.ru/asp.net/rss.xml");
            return _request.BeginGetResponse(cb, extraData);
        }
        public void EndProcessRequest(IAsyncResult result)
        {
            string rss = String.Empty;
            WebResponse response = _request.EndGetResponse(result);
            using (response)
            {
               StreamReader reader = new StreamReader(response.GetResponseStream());
               rss = reader.ReadToEnd();
            }
            _context.Response.Write(rss);
        }
        public bool IsReusable
        {
            get { return true; }
        }
        public void ProcessRequest(HttpContext context)
        {
            throw new Exception("The ProcessRequest method is not implemented.");
        }
    }
}
Register it in your web configuration file. 
File: Web.Config
<configuration>
    <system.web>
      <httpHandlers>
        <add path="*.rss" verb="*" type="MyNamespace.RSSHandler"/>
      </httpHandlers>
    </system.web>
</configuration>
If you have a news reader, such as SharpReader, then you can enter a path like the following in the reader"s address bar:
http://localhost:2026/YourApp/news.rss
File: ShowRSSHandler.aspx
<%@ Page Language="C#" %>
<%@ Import Namespace="System.IO" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
    void Page_Load()
    {
        string pagePath = Request.Url.OriginalString;
        string rssPath = Path.ChangeExtension(pagePath, ".rss");
        srcRSS.DataFile = rssPath;
    }
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Show RSS Handler</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:GridView
        id="grdRSS"
        DataSourceID="srcRSS"
        AutoGenerateColumns="false"
        Runat="server">
        <Columns>
        <asp:TemplateField HeaderText="Articles">
        <ItemTemplate>
            <asp:HyperLink
                id="lnkRSS"
                Text="<%# XPath("title") %>"
                NavigateUrl="<%# XPath("link") %>"
                Runat="server" />
        </ItemTemplate>
        </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <asp:XmlDataSource
        id="srcRSS"
        XPath="//item"
        Runat="server" />
    </div>
    </form>
</body>
</html>

Source viewer Http Handler

using System;
using System.Web;
using System.IO;
public class SourceHandler : IHttpHandler{
  public void ProcessRequest(System.Web.HttpContext context)
  {
    HttpResponse response = context.Response;
    HttpRequest request = context.Request;
    HttpServerUtility server = context.Server;
    response.Write("<html><body>");
    string file = request.QueryString["file"];
    try
    {
      response.Write("<b>Listing " + file + "</b><br>");
      StreamReader r = File.OpenText(server.MapPath(Path.rubine("./", file)));
      string line = "";
      while (line != null)
      {
        line = r.ReadLine();
        if (line != null)
        {
          response.Write(server.HtmlEncode(line) + "<br>");
        }
      }
      r.Close();
    }
    catch (ApplicationException err)
    {
      response.Write(err.Message);
    }
    response.Write("</html></body>");
  }
  public bool IsReusable
  {
    get { return true; }
  }
}

ASP.NET Tutorial/Development/HTTP Handlers — различия между версиями

Текущая версия на 11:56, 26 мая 2010

Содержание

Creating a Custom HTTP Handler

Creating a Generic Handler

Creating HTTP Handlers

HelloWorld HttpHandler (VB)

Implementing the IHttpHandler Interface

Log user in HttpModule

RSS Handler

Source viewer Http Handler

Навигация

Персональные инструменты

Пространства имён

Варианты

Просмотры

Ещё

Поиск

Разделы

Инструменты

Навигация

Текущая версия на 11:56, 26 мая 2010 (просмотреть исходный код) Admin (обсуждение \| вклад) м (1 версия)	Текущая версия на 11:56, 26 мая 2010 (просмотреть исходный код) Admin (обсуждение \| вклад) м (1 версия)
(нет различий)