io Programmo 40/IOPROG_40.ISO/SOFT/NETFrameworkSDK.exe/comsdk.cab/samples.exe/QuickStart/aspplus/doc/httphandlers.aspx

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<h4>HttpHandlers and Factories</h4>

<div class="indent" style="font-family:Verdana; font-size:8pt;">
    <b> <img align="middle" src="/quickstart/images/bullet.gif">  </b>
    <a class="toc2" target="content" href="#overview">Overview</a><br>
    <b> <img align="middle" src="/quickstart/images/bullet.gif">  </b>
    <a class="toc2" target="content" href="#declaring">Configuring HttpHandlers and Factories</a><br>
    <b> <img align="middle" src="/quickstart/images/bullet.gif">  </b>
    <a class="toc2" target="content" href="#customhandler">Creating a Custom HttpHandler</a><br>
</div>

<p>
<hr>


<!--BEGIN SECTION-->
<a name="overview">
<span class="subhead">Overview</span>
<p>

ASP+ provides a low-level request/response API that enables developers to use
NGWS Runtime classes to service incoming HTTP requests. Developers accomplish
this by authoring classes that support the <b>System.Web.IHTTPHandler</b> interface
and implement the <b>ProcessRequest()</b> method.  Handlers are often useful when
the services provided by the high-level Page Framework abstraction are not required
for processing the http request.  Common uses of handlers include filters and
CGI-like applications, especially those that return binary data.

<p>
Each incoming HTTP request received by ASP+ is ultimately processed by a specific
instance of a class implementing <b>IHTTPHandler</b>. <b>IHTTPHandler Factories</b> provide the infrastructure
that handles the actual resolution of URL requests to IHTTPHandler instances.
ASP+ ships with three standard IHTTPHandler factories - PageFactory,
RestrictedResourceFactory, and WebServiceFactory.
Developers can optionally create and register additional factories to support
richer request resolution and activation scenarios.

<!--BEGIN SECTION-->
<br>
<a name="declaring">
<br>
<span class="subhead">Configuring HttpHandlers and Factories</span>
<p>

Http Handlers and Factories are declared in the ASP+ configuration as part
of a config.web file. ASP+ defines an "httphandlers" configuration section
where handlers and factories can be added and removed. Settings for
HttpHandlerFactories are inherited by sub-directories, settings for HttpHandler are NOT
inherited.
<p>

ASP+ for example maps all requests for .aspx files to the <b>PageHandlerFactory</b> class in
top config.web:

<div class="code"><pre>
<httphandlers>
  ...
  <add verb="*" path="*.aspx" type="System.Web.UI.PageHandlerFactory" />
  ...
</httphandlers>
</pre></div>

<!--BEGIN SECTION-->
<br>
<a name="customhandler">
<br>
<span class="subhead">Creating a Custom Http Handler</span>
<p>

In the following sample a custom <b>HttpHandler</b> is created, which handles
all requests to "SimpleHandler.aspx" in the respective directory.
<p>

<Acme:SourceRef
  RunSample="/quickstart/aspplus/samples/apps/handler/simplehandler.aspx"
  ViewSource="/quickstart/aspplus/samples/apps/handler.src"
  Icon="/quickstart/aspplus/images/simplehandler.gif"
  Caption="SimpleHandler"
  runat="server" />
<p>


A custom HTTP handler can be created by implementing the IHttpHandler
interface, which contains only two methods. By calling <b>IsReusable</b> a
HTTP factory can query a handler to determine whether the same instance can be used to service multiple requests. The
ProcessRequest method takes an <b>HttpContext</b> instance as a parameter, which
gives it access to the <b>Request</b> and <b>Response</b> intrinsics.
In this sample, request data is ignored and a constant
string is sent as a response to the client:

<div class="code"><xmp>
public class SimpleHandler : IHttpHandler
{
  public void ProcessRequest(HttpContext context)
  {
    context.Response.Write("Hello World!");
  }

  public bool IsReusable()
  {
    return true;
  }
}
</xmp></div>

After placing the compiled handler assembly in the application's /bin directory,
the handler class can be specified as a target for requests. In this case all
requests for "SimpleHandler.aspx" will be routed to an instance of the
SimpleHandler class, which lives in the namespace Acme.SimpleHandler:

<div class="code"><xmp>
<httphandlers>
  <add verb="*" path="SimpleHandler.aspx" type="SimpleHandler#Acme.SimpleHandler" />
</httphandlers>
</xmp></div>

<p>

<h4>Section Summary</h4>
<ol>
<li>HTTP Handlers and Factories are the backbone of the ASP+ framework.
<li>Factories assign each request to one handler, which processes the request.
<li>Factories and handlers are defined in the config.web file. Settings for factories
are inherited by sub-directories.
<li>To create a custom handler, implement IHttpHandler and add the class in the
httphandlers section of the config.web in the directory.
</ol>
<p>

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