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This article mainly shows you "how to use HttpHandler and HttpModule", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "how to use HttpHandler and HttpModule" this article.

Mysterious HttpHandler and HttpModule

I started to learn asp.net from dragging controls in college, and I don't know much about. Net class library objects. So when I see everyone writing some personalized asp.net nouns, I feel that there is always a mysterious veil over asp.net, which makes me wonder. I believe that there are many .net siege masters in the garden who are similar to my experience. In the past, both HttpHandler and HttpModule were mysterious. Haha, today I will show you my understanding and application of him.

Maybe you don't understand HttpHandler and HttpModule, maybe you don't know the use of HttpHandler and HttpModule, maybe you don't seem to understand. Today, please let me show you the elegant demeanor of HttpHandler and HttpModule. Today I want to make him So Easy!

Understand asp.net pipeline events

What is the asp.net pipeline? To put it simply, the life cycle of a page is a series of events done by asp.net from the time the page is requested to the time it is displayed in your browser. The following shows you these events (see with Fish Li).

1. Validating the request examines the information sent by the browser and determines whether it contains potentially malicious tags. For more information, see ValidateRequest and script intrusion Overview.

two。 If any URL has been configured in the UrlMappingsSection section of the Web.config file, URL mapping is performed.

3. Raises the BeginRequest event.

4. Raises the AuthenticateRequest event.

5. Raises the PostAuthenticateRequest event.

6. Raises the AuthorizeRequest event.

7. Raises the PostAuthorizeRequest event.

8. Raises the ResolveRequestCache event.

9. Raises the PostResolveRequestCache event.

10. Based on the file extension of the requested resource (mapped in the application's configuration file), the class that implements IHttpHandler is selected to process the request. If the request is for an object derived from the Page class

Page, and the page needs to be compiled, ASP.NET compiles the page before creating an instance of the page.

11. Raises the PostMapRequestHandler event.

twelve。 Raises the AcquireRequestState event.

13. Raises the PostAcquireRequestState event.

14. Raises the PreRequestHandlerExecute event.

15. Call the ProcessRequest method (or asynchronous version of IHttpAsyncHandler.BeginProcessRequest) of the appropriate IHttpHandler class for the request. For example, if the request is for a page, the

The current page instance will process the request.

16. Raises the PostRequestHandlerExecute event.

17. Raises the ReleaseRequestState event.

18. Raises the PostReleaseRequestState event.

19. If the Filter property is defined, response filtering is performed.

20. Raises the UpdateRequestCache event.

21. Raises the PostUpdateRequestCache event.

twenty-two。 Raises the EndRequest event.

23. Raises the PreSendRequestHeaders event.

24. Raises the PreSendRequestContent event.

Note:

1. Keep in mind that the above events are not written blindly, let alone in their order. They are triggered from the beginning of the request to the end of the presentation of the page, from one to 24, from top to bottom.

two。 Not every event that starts with BeginRequest is triggered because Response.End () can be called at any time during the entire process or an unhandled exception occurs to end the process ahead of time. Of all the events, only the EndRequest event is certain to trigger, and the (partial Module) BeginRequest may or will not be triggered.

3. If it is IIS7, the 10th event is the MapRequestHandler event, and two other events have been added before the EndRequest event: LogRequest and PostLogRequest. MapRequestHandler, LogRequest, and PostLogRequest events are supported only if the application is running in IIS 7.0 integrated mode and in conjunction with .NET Framework 3.0 or later.

Summary: these events we are free to add methods, classes, properties and other columns to the events you need for your own actions on the request. That is to say, we used to program at the page level, but now we can process projects and requests at the request level. How to do it depends on the magic of HttpMoudle and HttpHandler below.

Understand HttpHandler and HttpModule

Let's start with HttpHandler.

First of all, you should understand how asp.net handles our request files, not to mention the seemingly lower mystery veil that has nothing to do with asp.net, so how does .net deal with our request files? Let me show you something.

Open the web.config file in the C:\ WINDOWS\ Microsoft.NET\ Framework\ v2.0.50727\ CONFIG\ directory on your computer. Find the httpHandlers node and see what it says below. Look at me if you don't want to open it.

The copy code is as follows:

View Code

The above code is understood like this: different file types are mapped to different Handler in the node, and for .aspx, it is handled by System.Web.UI.PageHandlerFactory. For .cs, it is handled by System.Web.HttpForbiddenHandler.

The above is the default Handler processing, of course, after knowing the HttpHandler, we can also register our own HttpHandler, write our own HttpHandler handlers, and deal with different types of files. I will implement this later and show you.

Question: since the role of HttpHandler is to map files with different types of suffixes in the request to different handlers, at which time in the page life cycle does the handler map the request?

Answer: according to the 24 events above, the mapping in this HttpHandler node is triggered in step 10. He maps to different handlers in which the implementation of methods and classes is triggered in step 15.

Besides, HttpModule.

HttpHandler is for a type of file, mapped to the specified handler to make the request. And the mapping, and processing, all take place in events that asp.net has specified.

HttpModule, on the other hand, maps all request files to specified handlers to process requests, and these processes can occur in any event in the request pipeline. That is to say, which event you subscribe to, this write processing occurs in that event, and then executed after processing, the next event of the event you have subscribed to, of course, you can also terminate all events and run the last event directly, which means that it can not give HttpHandler a chance, a very powerful HttpModule.

The use of HttpHandler

The use of HttpHandler is demonstrated by a hotlink protection technology.

1. Register HttpHandler first: register in Web.config

The copy code is as follows:

The registration above is to map the request for a file in jpg format in the website to the assembly ProcessHandler_test with the namespace httphander_test class named CustomHandler to process the request.

two。 If you want to process the request through HttpHandler, you must implement the interface IHttpHandler in the mapped handler

3. The program code that is mapped to is as follows

The copy code is as follows:

View Code

Namespace httphander_test

{

Public class CustomHandler: IHttpHandler

{

Public void ProcessRequest (HttpContext context)

{

/ / obtain the physical path of the file server

String FileName = context.Server.MapPath (context.Request.FilePath)

/ / if UrlReferrer is empty, a default image that forbids hotlink is displayed.

If (context.Request.UrlReferrer.Host = = null)

{

Context.Response.ContentType = "image/gif"

Context.Response.WriteFile ("/ error.gif")

}

Else

{

/ / if the domain name of the host of your site is not included in the UrlReferrer, a default image that forbids hotlink is displayed.

If (context.Request.UrlReferrer.Host.IndexOf ("yourdomain.com") > 0)

{

Context.Response.ContentType = "image/gif"

Context.Response.WriteFile (FileName)

}

Else

{

Context.Response.ContentType = "image/gif"

Context.Response.WriteFile ("/ error.gif")

}

}

}

Public bool IsReusable

{

Get {throw new NotImplementedException ();}

}

}

}

Press Ctrl+C to copy the code above this simple example is completed, if there is a request for a file in Jpg format, rather than in the domain name of this site, then a specified error image will be output to replace the original connection image.

Conclusion: the function of httpHandler is much more than that. I hope you can understand that he is handling a kind of file request, and that you can understand his event location in the request pipeline, which will be more helpful for you to understand.

The use of HttpModule

Because HttpModule is too powerful, that is to say, any request must go through a registered HttpModule handler, so when you use him, you must make a good judgment on all kinds of requests, that is, what requests to deal with, just let this request go to that handler, and don't let him execute every method. If you don't burden the program, the loss outweighs the gain.

Using HttpModule is similar to the steps of HttpHandler, while HttpModule implements the IHttpModule interface.

The above is all the contents of the article "how to use HttpHandler and HttpModule". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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