WebRAD: Building Database Applications on the Web with Visual FoxPro and Web Connection

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2 WebRAD: Building Database Applications on the Web with Visual FoxPro and Web Connection Harold Chattaway Randy Pearson Whil Hentzen Hentzenwerke Publishing

3 Published by: Hentzenwerke Publishing 980 East Circle Drive Whitefish Bay WI USA Hentzenwerke Publishing books are available through booksellers and directly from the publisher. Contact Hentzenwerke Publishing at: (fax) WebRAD: Building Database Applications on the Web with Visual FoxPro and Web Connection By Harold Chattaway, Randy Pearson, and Whil Hentzen Technical Editor: Barbara Peisch Copy Editor: Farion Grove Copyright 2002 by Harold Chattaway, Randy Pearson, and Whil Hentzen All other products and services identified throughout this book are trademarks or registered trademarks of their respective companies. They are used throughout this book in editorial fashion only and for the benefit of such companies. No such uses, or the use of any trade name, is intended to convey endorsement or other affiliation with this book. All rights reserved. No part of this book, or the ebook files available by download from Hentzenwerke Publishing, may be reproduced or transmitted in any form or by any means, electronic, mechanical photocopying, recording, or otherwise, without the prior written permission of the publisher, except that program listings and sample code files may be entered, stored and executed in a computer system. The information and material contained in this book are provided as is, without warranty of any kind, express or implied, including without limitation any warranty concerning the accuracy, adequacy, or completeness of such information or material or the results to be obtained from using such information or material. Neither Hentzenwerke Publishing nor the authors or editors shall be responsible for any claims attributable to errors, omissions, or other inaccuracies in the information or material contained in this book. In no event shall Hentzenwerke Publishing or the authors or editors be liable for direct, indirect, special, incidental, or consequential damages arising out of the use of such information or material. ISBN: Manufactured in the United States of America.

4 vii List of Chapters Chapter 1: Introduction 1 Chapter 2: What is Web Connection? 3 Chapter 3: Installing, Configuring, and Testing Web Connection 5 Chapter 4: Your First Web Connection Application 47 Chapter 5: How the Internet Works 91 Chapter 6: Complete Web Development Environment 107 Chapter 7: Server Hardware and Hosting 129 Chapter 8: Configuring Server Software 145 Chapter 9: How a Web Page Works 171 Chapter 10: Getting in Tune: Overcoming Conceptual Hurdles 201 Chapter 11: Managing Your Configuration 227 Chapter 12: A Web Connection Application from Start to Finish 247 Chapter 13: Identifying Users and Managing Session Data 307 Chapter 14: COM vs. File-Based Messaging 327 Chapter 15: Data Entry on the Web 347 Chapter 16: Extending the Framework 373 Chapter 17: The Mistakes We All Make 403 Chapter 18: Advanced Troubleshooting and Maintenance 415 Chapter 19: Asynchronous and Scheduled Operations 445 Chapter 20: Updating to New Web Connection Versions 469 Chapter 21: Marketing Your Web Site 477 Appendices (electronic download only) Appendix A: The West Wind Web Monitor Appendix B: TODO Installation Instructions Appendix C: Framework Elements and File Locations Appendix D: WebRAD Project Wizard Appendix E: Setting Up Multiple Domain Names on One IIS Web Server Appendix F: Setting Up SSL Appendix G: Online Store Considerations Appendix H: Using InstallShieldExpress for Visual FoxPro

5 Chapter 1: Introduction 1 Chapter 1 Introduction Presumably you ve picked up this book because you want to use Visual FoxPro to do Web development. Well, prepare yourself for some radical changes. My own experience reminds me of what my wife said when my daughter was born. She kept telling me, Your life will never be the same from this moment on At first I did not believe her after all, how much could a little seven-pound human change my life? Boy was I wrong! It is pretty much the same transition moving from doing traditional desktop development to doing Web applications. All the simple things suddenly become more involved and complicated. In Visual FoxPro, we have been spoiled. VFP has a mature fully OOP Forms Designer. We can create a library of base classes from which objects on our forms are built. We can simply drag and drop them onto a form and have them bound to a datasource. We can drag and drop a whole table, either local or remote, onto a form and have it become a grid. We have an integrated report writer, not state-of-the-art but very powerful none the less. In short, the entire VFP IDE is wrapped around data. There are no boundaries among the various components, from the language to the forms designer, class designer, and report designer. The entire environment has been designed around building database applications. In building desktop apps, the developer did not have to know about MS Internet Information Server, FTP, SSL, how to secure a Web server from hackers, the complexities of HTML, XML, session management, stateless programming, Web site testing and promotion, browser compatibility, and Cascading Style Sheets. Doing Web development will be like going back to using FoxBASE in some regards. The tools are still very immature compared to desktop tools, but they are getting better rapidly. VFP has evolved from a simple DOS application, starting with the original FoxBASE program in the early 80s. I ll always remember using Fox for the first time. Without making any changes to my Dbase application, I simply compiled it under FoxBASE and got a tremendous performance boost. Fox has always been about speed in handling data. It proves how even an interpreted language can compete with native code environments. With the advent of VFP, the string processing abilities of the language have also been dramatically improved. A great deal of the work in displaying Web pages is in the form of string manipulation. We will see how Web pages can be built using templates that VFP can parse and populate with data, or how an entire table can be converted into HTML in sub-second fashion. The amount of code that is run when evaluating a template is truly amazing. With the data and string manipulation engines in VFP, the response times are so fast that millions of hits a day can be processed by a VFP Web site without too much difficulty. Things have changed. No longer is it possible to get away with just knowing the VFP language and its design surfaces. The new technologies are not nearly as integrated. The Web page is not a native component of the VFP IDE. Not only is it not integrated, it does not even use the same language to display information. HTML is the language of the Web for formatting information. This is a bit daunting at first, but soon you will be using VFP to write HTML!

6 2 WebRAD: Building Database Applications on the Web This book is intended to serve as a comprehensive introduction for the VFP developer to move into the world of Web development. At the end of many chapters is a Chapter resources section that will reference other works that will help in understanding the material. I believe you will find it very exciting to learn about how these technologies work together and how they can leverage the incredibly powerful language that VFP developers have at their disposal. We will be using the Web Connection framework from West Wind Technologies ( as the basis for all examples in this book. Web Connection is an incredibly robust set of VFP classes that form the foundation for VFP Internet applications. WC is well supported by the author and has a strong development community. Who should be reading this book? This book is meant for Visual FoxPro developers who have a good grasp of object-oriented programming (OOP). The Web Connection framework is built on classes, so knowing how to perform subclassing and understanding inheritance is very important. A discussion of OOP principles is beyond the scope of this book. You do not need to know anything about Web development. This book will cover what is needed in HTML, layout tools, and the other related technologies. None of the other tools in VFP are covered other than using the Program Editor. The Forms Designer and Report Writer are not relevant for doing Web development. As different as Web development is from desktop development, Web Connection does allow you to preserve your investment in the VFP language. All of the middle-tier type programming is still done using the VFP language. So put your thinking caps on and prepare for a new way of doing development!

7 Chapter 2: What is Web Connection? 3 Chapter 2 What is Web Connection? Out of the box, Visual FoxPro has no knowledge of how to process a Web request. What Web Connection provides are the foundation classes that are needed to connect Visual FoxPro to the Web. Except for two small DLL files (WC.DLL and WWIPSTUFF.DLL), Web Connection is all native VFP code. There are classes that handle server functions like waiting for a request, determining what the request is, parsing the incoming data from a Web form, and then sending the result back out to the browser. When a request is made of the server, there is the class WWREQUEST. It is responsible for pulling apart a Web form, for example, so its information can be saved and manipulated. On the outgoing side, there is the WWRESPONSE class that contains methods for returning information back to the user, which is the response to a request. This class also contains methods that allow developers to create HTML templates with ASP style tags that can contain VFP expressions. The methods in WWRESPONSE can then parse the template and fill in the template expressions. This is probably one of the most powerful features of Web Connection. This template technology allows the entire VFP language to be exposed to the Web via simple ASP tags. The expression can be as simple as <%=date()%>, which would return the current date, or as complex as a call to a VFP method that makes full use of the VFP data and OOP language. There are also classes to handle cookie management and session management. One of the biggest changes in Web development is the stateless nature of Web applications. There are no persistent connections from the GUI to the data as there is in desktop apps. This change in development is handled quite nicely in the Web Connection framework. The WWSESSION class allows a user to have a continuous conversation with the server. In short, the WC framework provides all the foundational code that allows a new developer to get a simple Web site up in about 30 minutes. Apart from the core foundation classes, WC also provides a number of utility classes. One function that is part of the WWIPSTUFF class allows your applications to perform ing functions. It is possible to programmatically send whenever an event occurs. For example, when a new customer signs up, you could send an to your account to notify you. Another very practical use of ing is when an error occurs in your app, the error trapping code can send you an notification. WC also provides a WWXML class for XML parsing and generation. You can easily take a Visual FoxPro cursor and convert it to XML with a one-line call. You can also use the WC libraries to parse an XML string and store it into a table. WC also provides the class libraries to implement the MS SOAP protocols. SOAP, or Simple Object Access Protocol, is basically the API for the Web. You can use the SOAP interface to expose methods of your Web site to the outside world. Instead of only providing the traditional Web interface, you could expose links that take SOAP messages. This could allow your users to request and post information from other applications, even desktop applications, without going through the conventional Web form. For example, if your

8 4 WebRAD: Building Database Applications on the Web interface requirements are too extensive for a Web page, you could design an application that runs as a normal desktop app but accesses the Web underneath. You really do not have to know the complete inner workings of the WC framework in order to use it. It is sufficient to know the available functions and methods and build your application using them. What Web Connection is not Web Connection does not allow you to take an existing desktop application and simply run it on the Web. Taking a VFP form and duplicating it on the Web is not a trivial task. There are many more events and more form objects available on the desktop. Doing things like page frames in native HTML is virtually impossible. Dynamic HTML is required for something like this, and the browsers (Internet Explorer, Netscape) do not treat dynamic HTML in the same way. The major downside to a Web-based application is accounting for the different run-time environments that can be encountered. In VFP, the same run time is evaluating the form no matter where the app is run. With a Web application, you cannot count on a particular browser always being used and programming to it. Major functional differences exist between browser versions as well. Also, Web Connection is not a pre-packaged template for building an online store. There is a separate product available called the WebStore for that. WC is meant to be a more generalpurpose framework. Updates Thanks to the magic of inheritance, updates to the Web Connection framework are very easy. Most of the time, you can simply copy the new class libraries over the old ones. The updates to the WC libraries happen fairly frequently. There are some updates that affect the WCONNECT.H file that contains a large number of #DEFINEs that configure the framework. Also, there might be updates to the WC.INI file. Updates to these files are best done with a tool like Beyond Compare. This is a vdiff or visual difference tool that will be discussed in detail later on. It allows you to compare two files side by side and move changed lines from one file to the other. It is an extremely helpful tool. Conclusion Do not be afraid of all the new terminology! This book is targeted to new Web developers and will cover all these new concepts in detail.