ASP Internals

by Jon Flanders

Paperback: 160 pages
Publisher: Addison-Wesley Pub Co
ISBN: 0201616181; 1st edition (December 15, 2000)

A concise guide to Microsoft's Active Server Pages in which software developer and instructor Flanders shows how to enhance the technology with the Component Object Model to create dynamic Web applications that are more scalable and robust. The ASP source code is private property and therefore secret, so he has created a clone to work with. He does not provide a bibliography.

From the Inside Flap: The Active Server Pages (ASP) runtime was designed to provide an easy way to create dynamically generated HTTP response packets. On this count, the designers of ASP get an A.

Most of the day-to-day use of ASP is also this easy. Many times, developers feel the need to push the envelope of what a particular technology was designed to do. Whether just for fun or based upon a real application requirement, pushing that envelope can be frustrating. In order to push the envelope with ASP, you need to understand how it works, how each piece is put together.

If you are interested in learning what ASP is or how to program ASP in general, this is not the book for you. You should read this book once you have a solid understanding of ASP programming in general. This book is meant to peel back the cover on ASP and look inside. I will peer into the plumbing and show how ASP does what it does. My goal is that, after reading this book, you will be a better ASP and COM programmer by understanding how the pieces fit together, not because I showed you the best way to write a loop in VBScript.

It would be helpful to us as developers to have the source code for ASP, even if only to help us debug our own code. Until Microsoft completely embraces the Open Source movement (don't hold your breath), we have no real way of knowing what the internals of ASP really look like. I can guess based on what I know about how ASP works. In this book, I will implement a "clone" of ASP. I have decided to name this clone "Active COM Pages" (or "ACP" for short). Instead of showing you the source code of ASP, I will show you the source code of ACP. ACP in most ways will behave exactly as ASP does (and when it doesn't or can't, I will point that out).

A few caveats about my implementation. First, it does not act like ASP in all ways. It isn't meant to be a replacement for ASP, only a reference to help understand ASP itself. Second, the ACP implementation isn't production code that I recommend using in a real system. Again, it is the bare minimum needed to replicate the important functionality of ASP.

I hope that seeing what ASP does under the covers (approximately, at least) will help you better understand how to put together your own ASP applications.

Intended Audience. This book is written for anyone who wants to know more about the internal workings of ASP (hence the title). You should be a seasoned ASP developer who has a firm grasp of COM (Microsoft's Component Object Model). (For two good books on COM, see Don Box, Essential COM, Addison-Wesley, 1998, and Ted Pattison, Programming Distributed Applications with COM+ and Microsoft Visual Basic 6.0, Microsoft Press, 2000.)

All of the ASP code in this book is written in VBScript. The code implementing ACP (my ASP clone) uses C++ (including some classes from the Standard Template Library-STL). This is necessary because of the underlying architecture. ATL (Microsoft's Active Template Library) is used to implement the COM classes used inside of ACP. Even if you are not familiar with C++ or ATL, the code comments and explanations will help you understand how ASP works.

What to Expect Each chapter of this book covers a particular aspect of the ASP runtime.

Chapter 1, "Introduction," provides an introduction to the Hypertext Transfer Protocol (HTTP). In the end, everything in ASP is translated to and from HTTP. This chapter includes a brief description of how HTTP works.

Chapter 2, "IIS and ISAPI," explains how IIS (Internet Information Server, which hosts ASP) is put together and how ASP uses ISAPI (Internet Server Application Programming Interface) to do the majority of its work.

Chapter 3, "Active Scripting," focuses on hosting the Active Script Engine interfaces, which ASP uses to do the majority of its heavy lifting, and on adding named objects to running scripts.

Chapter 4, "Wrapping HTTP," discusses ASP's IResponse and IRequest interfaces and how they interact with the HTTP protocol through ISAPI.

ASP provides built-in state management at both the session and application level. Chapter 5, "State Management," discusses the interfaces used to provide state management and how to avoid performance problems that can arise if the interfaces are not used judiciously.

ASP's and the scripting engines' integration with COM is one of the best features of the runtime. How COM objects are created and how they interact with ASP are the subjects of Chapter 6, "IServer and Components."
ASP also integrates with the COM+ transactional services. Chapter 7, "Transactions," shows how ASP achieves this integration.

The Internet has made global distributed applications a reality. ASP has built-in features that enable you to write internationalized applications as Chapter 8, "Internationalization," will show. Jon Flanders

From the Back Cover: Microsoft's Active Server Pages (ASP) is the standard technology for creating dynamic Web pages, but ASP alone does not allow Web developers to create scalable Web applications. Microsoft's Component Object Model (COM) is the key that can turn good ASP applications into powerful, multi-tiered, scalable applications that are e-commerce-ready. ASP Internals examines the inner workings of ASP and shows readers how it interfaces with COM, enabling them to develop outstanding Web applications.

Because the source code for ASP is not openly available, author Jon Flanders has created an ASP clone, Active COM Pages (ACP). In revealing its source code, he provides a view under the hood of ASP so developers can finally see and understand how it works and how they can most effectively work with it.

ASP Internals covers each aspect of the ASP runtime. It demonstrates ASP integration with COM+ transactional services. And, most important, it shows readers how COM objects are created and interact with ASP. Other important topics include:
• How ASP is translated to and from the HTTP protocol
• ASP, IIS, and ISAPI, including threads, security, and the Web Application Manager
• Active Scripting, with an explanation of how to add named objects to running scripts
• ASP's IResponse and IRequest interfaces and how they interact with HTTP through ISAPI
• ASP state management at the session and application levels, and related performance issues
• How ASP and the Scripting Engine integrate with COM
• ASP integration with COM+ transactional services
• ASP's built-in internationalization features, including a look at Unicode

Numerous code examples, written in VBScript, demonstrate best practices for performing vital programming tasks.

Written for Web developers who are familiar with ASP and COM, ASP Internals shows readers how to make the best of both technologies in the creation of dynamic, high-quality, database-driven Web applications.

About the Author: Jon Flanders is a software engineer and instructor at DevelopMentor specializing in ASP and COM. Previously he worked as an architect and consultant on various large-scale, ASP-based applications. He is a frequent lecturer and writer on ASP and COM.

Customer Reviews
Nice peek into ASP, but...., February 26, 2001
Reviewer: A reader from Nashua, NH USA
This book gives you a great look into the implementation of ASP, and its conciseness is appreciated. However, two factors prevented me from giving it a higher rating: (1) No pointers to where the source code may be available. (If the code is not publicly available, please say so in the book). I did send the publishers email asking them about this, but never heard back. (2) Numerous typos - these were more of an annoyance, but were surprising given the consistent high quality of other books in the Developmentor series.

The view of ASPs from underneath, December 10, 2000
Reviewer: Charles Ashbacher from Hiawatha, Iowa United States (ashbacher@ashbacher.com)
A few years ago, I started an introductory course in Active Server Pages and wrote my own instructional material. Although it has always gone well, until now, I had never made the attempt to get deep under the hood and examine what is happening behind the scenes. It always seemed that delving into the C++ code would be a low Return On Investment (ROI) operation. When I first received this book, I read the blurbs and was somewhat skeptical. However, once I started, the reading was completed in less than a day, and the ROI was rather high. It was gratifying to learn that some of the implementations were as I had always suspected. The basics of underlying data transfer are thoroughly introduced and several of the points made in the book will be incorporated into the next rewrite of my ASP material. While it does help to understand C++, particularly Visual C++, it is not an absolute requirement.

I learned more about the underlying mechanics of IIS and ASPs in the reading of this book than I have in over six sessions of a class where students and I always tinker with the code. If you have more than a passing interest in coding ASPs, then this is a book that will be of enormous value in learning how things are executed. The knowledge will also help you understand some of those infuriatingly cryptic errors.

yeah, yeah, January 11, 2002
Reviewer: joeknow from Austin, Tx USA
Come on you bad reviewers. This book is pretty good. No, it's not end to end ASP Internals, but IIS isn't open source either. Interesting and informative coverage of SOME aspects of ASP. Transaction coverage is particuarly good.

A Very Good Resource To Know Pseudo Implementation of ASP, January 4, 2002
Reviewer: Naveen from Brookline,NH
I found the book to be a very good resource to see pseudo implementation of ASP. The explanation is as good as real inside impelementation of ASP. This is book is not about samples on how to use ASP to write your web pages. It is more about how ASP works.

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