04 HTTP Pipeline - Copy

8/6/2019 04 HTTP Pipeline - Copy

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HTTP PipelineASP.NET WebMethod Internals


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WebMethod Internals

WebMethod framework is built on .NET's HTTP pipeline

functionality provided by .asmx HTTP handler

(System.Web.Services.Protocols.WebServiceHandlerFactory)

Understanding the pipeline is essential

influences design choices

defines configuration options

provides extensibility hooks


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The HTTP Pipeline

System.Web defines a server-side HTTP pipeline pipeline can run on top of any Web server

pipeline configured via XML configuration files

many of the pipeline classes are extensible

applications, modules, and handlers define processing


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HTTP Pipeline Classes

HTTP Pipeline Classes

HttpWorkerRequest is low-level request

HttpRuntime is pipeline entry point

HttpContext wraps request in simpler object model

HttpApplicationFactory provides HttpApplication for vroot

HttpApplication processes messages via modules/handlers

IHttpModule classes pre-/post-process requests

IHttpHandlerFactory classes provide handler factories

IHttpHandler classes process requests and generate response


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Module

Module

Handler

HttpRuntime

HttpApplication

Factory

HttpApplication

Module

HandlerFactory

HttpContext

HttpRequestHttpRespons

e

IHttpModule

IHttpHandler-Factory

IHttpHandler

HTTP Pipeline


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Integration with IIS

Pipeline relies on IIS to receive/dispatch requests by default

requests dispatched by ISAPI extension: ASPNET_ISAPI.DLL

ASPNET_ISAPI.DLL passes requests through named pipe to a

worker process called ASPNET_WP.EXE

ASPNET_WP.EXE processes requests using HTTP pipeline

pipeline can be integrated with other web servers too


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inetinfo.exe

aspnet_isapi.dll

HTTP

aspnet_wp.exe

named pipe HttpRuntime

IIS and the HTTP Pipeline


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Pipeline Process Model

ASPNET_WP.EXE worker process completely configurable

ASPNET_ISAPI.DLL reads processModel configuration

configured in IIS Admin Console (Windows .NET Server)

configured in global machine.config file (Windows XP)

each worker process services unlimited requests by default

lifetime of worker process can be limited by several factors

when limit is reached, process is replaced with a new instance


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Implementing an HTTP handler

HTTP handlers process a request and generate a response

handlers are classes that implement IHttpHandler

pipeline calls ProcessRequest when request arrives

pipeline provides an HttpContext object

handlers can be instantiated by default factory

if handlers IsReusable property is true, handler will be reused


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namespace MyNamespace{public class BasicHandler : IHttpHandler{public void ProcessRequest(HttpContext ctx)

{ctx.Response.ContentType = "text/xml";ctx.Response.Write("");ctx.Response.Write(ctx.Request.Url);ctx.Response.Write("");

}

public bool IsReusable { get { return true; } }}

}

Implementing IHttpHandler


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HttpContext

The HttpContext class models HTTP message exchange

Properties hold references to HttpRequest, HttpResponse,

state management objects, etc.

Current context always available to processing thread via static

HttpContext.Current property


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HttpContext Property Description

Application Per-application cross-request state

Application Instance Application object processing request

Cache Per-application cached state

Handler Handler object processing request

Items Per-request state

Request HTTP request message

Response HTTP response message

Server Utility functionsSession Per-user cross-request state

User User information

HttpContext Properties


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Deploying an HTTP handler

Once an HTTP handler is implemented, it must be deployed

handler assembly placed in virtual directory's bin or GAC

You must also configure when the handler is called

using an .ashx file or

adding an entry to web.config and the IIS script map

\inetpub\wwwroot

\mathweb.config\binmath.dll

virtual directory

bin subdirectory


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Referencing Handlers from .ashx Files

Handlers can be referenced in .ashx files

allows deployment without touching IIS or configuration files

.ashx handler pre-configured with IIS during installation

.ashx WebHandler declaration references handler class

IHttpHandler-derived class


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.ashx and JIT Compilation

An .ashx file can directly contain IHttpHandler code JIT compiled during first invocation

using System.Web;

public class BasicHandler : IHttpHandler{...

}


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aspnet_isapi.dll

IIS Configuration


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HTTP Pipeline Configuration Hierarchy

HTTP pipeline is configured using a hierarchy of .config files root file in .NET installation directory (machine.config)

other files in virtual directories and subdirectories (web.config)

processing based on cumulative configuration data


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+

c:\winnt\Microsoft.NET\Framework\v1.x\CONFIG\machine.config

+

c:\inetpub\wwwroot\foo\web.config

c:\inetpub\wwwroot\foo\bar\web.config

http://www.baz.com/foo/quux.ashx

http://www.baz.com/foo/bar/quux.ashx

Pipeline Configuration Files


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Adding a Handler Mapping


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+

c:\winnt\Microsoft.NET\Framework\v1.x\CONFIG\machine.config

c:\inetpub\wwwroot\foo\web.config

http://www.baz.com/foo/quux.ashx

Removing a Handler Mapping


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Useful Predefined HTTP Handlers

Often useful to allow some operations but not others There are several predefined HTTP handlers to block requests

HttpForbiddenHandler

HttpMethodNotAllowedHandler

HttpNotFoundHandler

HttpNotImplementedHandler

There is a also a standard HTTP handler for static files

StaticFileHandler


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Mapping to Predefined HTTP Handlers


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WebMethod (.asmx) Handler

WebMethod functionality provided by .asmx handler

...


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WebMethods and the HTTP Context

WebMethods can access the current HttpContext Current static property accesses correct object for thread

Provides access to Session, Application, etc.

public class MathService{[WebMethod]public int Add(int n1, int n2){int sum = n1 + n2;HttpContext.Current.Application["last_sum"] = sum;return sum;

}}


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Deriving from WebService

WebService base class eases access to HttpContext provides public properties that expose HttpContext properties

Request and Response are notable exceptions

public class MathService : WebService{[WebMethod]public int Add(int n1, int n2){int sum = n1 + n2;Application["last_sum"] = sum;return sum;

}}


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HTTP Request

POST /math/add.asmx

INETINFO.EXE

(IIS)

aspnet_wp.exe

(ASP.NET Worker Process)

aspnet_isapi.dll(ASP.NET

ISAPI

Extension)

Built-in

.asmx

Handler

class

add.asmx

HTTP Response

HTTP/1.1200 OK ...

Assembly with

MathService

class

Compilesto

IHttpHandler

A Day in the Life of a WebMethod

IIS metabase

machine.config

.asmx mapsto

.asmx maps to

XmlSerializerAttributes

inform


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Summary

HTTP pipeline supports server-side HTTP programming The pipeline integrates with IIS (by default)

HTTP context modeled as hierarchy of objects

HTTP handlers are endpoints for HTTP messages

HTTP modules are intermediate filters for HTTP messages

HTTP application objects coordinate request processing,

tying modules and handlers together

Pipeline behavior is controlled via hierarchy of XML files


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References

HTTP Pipelines, MSDN Magazine,Ewald, Brown http://msdn.microsoft.com/msdnmag/issues/02/09/HTTPPipelin

es/default.aspx

Real World XML Web Services, Addison Wesley, Shohoud

Building XML Web Services for the Microsoft .NET Platform,

MSPress, Short

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04 HTTP Pipeline - Copy