ASP.NET HttpHandlers – Are they really required?

ASP.NET HttpHandler is a process that runs in response to a request that is made to an ASP.NET Web application. Almost everything we do in an HttpHandler, can be done in a normal .aspx page. So, why do we need HttpHandlers? Are they really required?

Given below is the explanation of why HttpHandlers are really required:

1. Reusability & Portability – HttpHandlers are more reusable and portable than normal .aspx pages. Since there are no visual elements in an HttpHandler, they can be easily placed into their own assembly and reused from project to project.
2. HttpHandlers are relatively less expensive than the PageHandler. A page goes through a set of events to be processed at the server (such as onInit, onLoad, etc.), ViewState and postbacks or simply the complete Page Life Cycle. When you really have nothing to do with the complete page life cycle (like displaying images), HttpHandlers are very useful.

Handlers in ASP.NET

Handler is an agent of communication or a medium which is responsible for communication in the absence of the actual user. Technically, a Handler is a class which is responsible for Instantiation of a class i.e; allocation of memory.

Console applications or Windows applications do not have handlers. We declare a class and create an object of that class in the Main() method. We as a developer are solely responsible for handling the class – specifically - instantiation of the class.

However, Web applications have handlers. In GUI Web Applications we never create an object of the “_default” page which inherits the Page class.

In Web Services, the Web Service class is never instantiated.

In WCF, the Service class, which inherits the IService Interface is never instantiated.

Now comes the question – Who instantiates the above mentioned classes?

Behind the scene, the Handler is responsible for instantiation of the above mentioned classes. ASP.NET maps HTTP requests to HTTP handlers based on the extension of the requested file (type of file). Each HTTP handler can process individual HTTP URLs or groups of URL extensions in an application. ASP.NET includes several built-in HTTP handlers:

a)    ASP.NET – System.Web.UI.PageHandlerFactory

b)    Web Service – System.Web.Services.Protocols.WebServiceHandlerFactory

c)    WCF – System.ServiceModel.Activation.ServiceHttpHandlerFactory

There are different drivers for different protocols. The driver or API of the protocol (ex – http.sys) has to have the ability to differentiate and resolve requests.

 

.sys files are the drivers for protocols. http.sys file is a driver or API or listener for the HTTP protocol. You can say that HTTP is abstraction, while http.sys is encapsulation. http.sys file handles the request and response in HTTP. The http.sys file is located in C:\Windows\System32\drivers\ folder.

When a request arrives on the server, the drivers for the protocols (.sys files) handles that request and forwards that request to a particular handler according to the extensions.

Conversion of Seconds to HH:MM:SS format

Recently I faced a requirement of converting seconds to HH:MM:SS format. After some R&D, I found the following solution:

CODE

DECLARE @in_seconds int

SET @in_seconds = 3661 -- One Hour One Minute and One Second

SELECT CONVERT(CHAR(8), DATEADD(SECOND, @in_seconds, 0), 108) As Hour_Minute_Second

OUTPUT

01:01:01

Note: This SQL code is applicable only for time less than 24 hours.

To overcome this limitation of 24 hours, I created the following function, which has the ability to return correct time duration for large time duration in seconds:

USE [AdventureWorks]
GO
/****** Object:  UserDefinedFunction [dbo].[fnc_convert_seconds_to_HHMMSS]    Script Date: 10/02/2013 08:48:33 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE FUNCTION [dbo].[fnc_convert_seconds_to_HHMMSS]
(
@dc_time decimal(18,2)
)

RETURNS VARCHAR(20)

AS

BEGIN
RETURN REPLACE(STR(CONVERT(INT,@dc_time/3600), LEN(LTRIM(CONVERT(INT,@dc_time/3600)))) + ':' + STR(CONVERT(INT,(@dc_time/60)%60), 2) + ':' + STR(@dc_time%60, 2), ' ', '0')
END

Example: SELECT dbo.fnc_convert_seconds_to_HHMMSS(36460) AS vc_time_in_HHMMSS

Output: 10:07:40