The 4D Web Companion. David Adams

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2 TABLE OF CONTENTS Welcome 1 About this Book 3 Overview... 3 Terminology... 5 Special Symbols Used in this Book... 5 Versions Covered... 5 About the Demonstrations... 6 About the 4D Code... 7 About the HTML... 8 About the Web Site... 8 Contact Information The One-Minute Guide to 4D Web Development 11 Introduction Tips for All Developers Advice for 4D Developers New to Web Development Advice for Developers New to 4D Advice for WebSTAR Users Advice for IIS Users D Web System Architecture and Tools 3 4D Web System Architecture 15 Introduction Where Is the Data? Where Is the Application Code? How Is the HTML Built? Where Is the HTML Stored? How Is the Web Server Integrated? D Web Tools 23 Introduction D s Contextual Mode The 4D Web Assistant D Semi-Dynamic Tags Active4D A Web Server Built with ITK Lasso-4D Integrating 4D with Another Web Server or System The Native 4D Web Server 33 Introduction Contextual Mode Non-Contextual Mode Semi-Dynamic Pages v

3 6 The 4D Web Assistant 37 Introduction A Quick Tour Configuration Advantages Disadvantages and Limits Active4D 43 Introduction Active4D Code Flow of Control Advantages of Active4D Disadvantages of Active4D Security and Configuration Concerns Tips D and CGI 49 Introduction Understanding CGI Calling CGI Programs through 4D Special Note: Calling CGIs from 4D Code Calling 4D as a CGI Integrating 4D with WebSTAR 55 Introduction Feature Overview Calling 4D from WebSTAR: Tools Overview WEBINCLUDE D Web Server Request Handling Response Page Templates D Connect and 4DSSI Security The Welcome Plug-in Monitoring and Debugging WebSTAR 4D Systems Integrating 4D with Windows Web Servers 71 Introduction DISAPI Versus NPH-CGI4D Mechanics: Special URLs for 4DISAPI and NPH-CGI4D Security Supported Request Types Request Headers ISAPI and NPH-CGI4D Responses Monitoring and Debugging Other Ways of Integrating Windows Web Servers and 4D Integrating 4D with Other Systems through HTTP 79 Introduction Overall Concept: Creating a Custom API Examples D Apache PHP ColdFusion IIS WebSTAR vi

4 Feature Overview 12 4D Web Server Chain of Events 91 Introduction Understanding 4D HTML Tag Categories Chain of Event Summaries Requesting a Standard URL Using a Link Requesting an Image Submitting a Form Semi-Dynamic Tags Related Chapters with More Information Web Feature Summary 99 Introduction Web Commands and Database Methods D HTML Request Keywords Magic URLs Database Parameters Semi-Dynamic Tags Web Processing Steps and 4D Features 103 Introduction The Overall Web Serving Process Making the Request Receiving and Dispatching the Request Analyzing the Request Setting the Response Processing the Response D Request Keywords Compared 107 Introduction Summary DACTION DSCRIPT DCGI DMETHOD On Web Connection 111 Introduction Basic Rules for On Web Connection Structuring the Code in On Web Connection Unknown URLs Contextual Mode Requests DCGI Calls Non-Contextual Mode 17 4DACTION 117 Introduction Mechanics Returning Information from a 4DACTION Method Chain of Events vii

5 18 4DCGI 123 Introduction Mechanics Chain of Events DCGI and On Web Connection Handling HTML Forms 127 Introduction Form Handling Defining an HTML Form DACTION versus 4DCGI Compiler_Web Uploading Files 135 Introduction An HTML File Upload Form What Happens when the User Submits the Form Limits and Risks Magic URLs 139 Introduction DBLANK DCACHECLEAR DHTMLSTATS DSTATS DWEBTEST Security Semi-Dynamic Pages 22 Semi-Dynamic Pages Overview 145 Introduction Semi-Dynamic Tag Summary Semi-Dynamic Pages Are Pure HTML Serving Static and Semi-Dynamic Pages Semi-Dynamic Pages and Web Processes Working with Semi-Dynamic Pages 151 Introduction Mechanics Semi-Dynamic Tag Categories Special Notes DSCRIPT 159 Introduction Mechanics Chain of Events When 4DSCRIPT Works Rules for Semi-Dynamic Callbacks Special Command Restrictions viii

6 25 4DVAR and 4DHTMLVAR 163 Introduction Mechanics DVAR versus 4DHTMLVAR Using 4DVAR and 4DHTMLVAR Limitations and Cautions Special Note: BLOBs and TEXT Resources DIF, 4DELSE, and 4DENDIF 173 Introduction Mechanics Special Notes and Suggestions Limitations and Cautions DLOOP and 4DENDLOOP 179 Introduction Mechanics Looping through an Array Looping through a Selection Looping Based on a Method Nesting Loops Special Notes DINCLUDE 187 Introduction Mechanics Special Content Handling Replacing 4DINCLUDE Contextual Mode 29 Contextual Mode Overview 195 Introduction Contextual Mode s Basic Features Problems with Contextual Mode Appropriate Uses for Contextual Mode Working with Contextual Mode 201 Introduction Contextual Mode Fundamentals Automatic Object Translation Building Forms for the Web Customizing Output Forms Customizing Incoming or Outgoing HTML with AP SET WEB FILTERS Creating Image Maps in Contextual Mode Embedding Custom HTML and JavaScript Developing in Contextual Mode Contextual Mode and Specific Commands DMETHOD 213 Introduction Mechanics Chain of Events ix

7 32 Automatic Image Maps 215 Introduction Basic Setup Clickable Images and Web Browsers Important Limitation AP SET WEB FILTERS 219 Introduction AP SET WEB FILTERS Background Example Tips and Warnings Security 34 4D Web Security Options 227 Introduction Password Options Settings On Web Authentication Use Passwords Include 4D Passwords Generic Web User Log Request On Web Authentication 235 Introduction Basic Rules for On Web Authentication About HTTP Basic Challenge-Response Authentication Managing 4D Database Access from the Web Custom Log-on Forms Using HTTP Basic Authentication Filtering Method Calls with On Web Authentication Secure Socket Layer (SSL) 245 Introduction Why Use SSL? D and SSL: Summary Preparing the 4D Web Server to Use SSL Configuring the 4D Web Server for SSL About SSL Working with Images 37 Serving Pictures 257 Introduction Serving Pictures in Contextual and Non-Contextual Modes Image Request Syntax How Picture Serving Works on the Web About Browsers and Pictures Serving Pictures in 4D Non-Contextual Mode x

8 38 Converting Pictures 265 Introduction Background: Picture Formats QuickTime Web-Oriented Picture Conversion Commands D 6.7 Picture Commands Advanced Picture Manipulation with QPix Special Picture Techniques 271 Introduction Serving Pages and Images from Different Machines Reducing Image Size Preventing Caching Problems with Dynamic Pictures Passing Information between Processes or Servers with Pictures Manipulating Pictures with 4D Picture Math HTML and Web Development 40 HTML and Web Resources 279 Introduction On-Line Resources Books Designing for the Web 283 Introduction Navigation Help Doesn t Know the Audience Be a User Users Matter The Clock Is Ticking Use Data-Driven Solutions Work with Others Integrating 4D with Dreamweaver and GoLive 287 Introduction The HTML Editor Integration Process GoLive Dreamweaver Special Notes HTML Tips and Suggestions 295 Introduction Respect the Medium Use Cascading Style Sheets Use a Standard HTML Version Format the HTML Source Use Comments Use a Visual Editor and a Text Editor Avoid Frames by Default Use Color Tastefully Adapt Images for the Web Avoid Gratuitous Animation Understand How Tables Work xi

9 44 HTML Form Tricks and Traps 301 Introduction Fields May Be Hidden Password Fields Obscure what Is Typed Fields May Be Submitted in any Order One Form May Have Multiple Submit Buttons Select Objects May Send Multiple Values for One Field Unselected Items Are not Submitted Documents May Be Uploaded Working with Paths 307 Introduction Web Roots Relative and Absolute Paths The Base Tag The Host Header Tag HTML Editors MIME 315 Introduction Web Browser Requests Web Server Responses Web Browser File Mapping Web Form Upload Fields MIME Types HTTP Fundamentals 319 Introduction General Features of HTTP Anatomy of HTTP Requests and Responses HTTP Requests Responding to a Web Page Request Debugging and Error Handling 48 Custom Error Pages 331 Introduction Background Handling Errors in On Web Connection Customizing 4D s Default Response Preventing and Handling Errors 337 Introduction Handle Errors Gracefully Reduce Errors by Using 4DCGI instead of 4DACTION Limit Direct Object References Track Errors with On Web Connection Trap Errors with ON ERR CALL Compile Defensively Test Early, Test Often Debugging Network Problems 343 Introduction Ping: Testing the Connection between Two Machines Trace Route: Testing the Connection Path Name Lookup: Testing that DNS Is Working xii

10 51 Debugging HTTP 347 Introduction Stream Capture Packet Capture and Analysis D Web Techniques 52 Virtual Paths 355 Introduction The Technique Using 4DCGI instead of 4DACTION Managing Bad URLS Filtering Forbidden Keywords with On Web Authentication Using Virtual Paths Selectively Custom Magic URLs 359 Introduction Implementing Magic URLs Custom Magic URLs for System Administrators Custom Magic URLs for Other Applications Referring to 4D Objects Indirectly 363 Introduction Adding an Abstraction Layer Abstraction and 4D Tags Methods D Functions in Expressions Web Process Initialization and Deinitialization 369 Introduction Background Review Initialization Using Compiler_Web Initialization Using On Web Authentication Recommended Strategy Deinitialization Strategy Controlling Initialization and Deinitialization from the Web Page Parsing Requests 377 Introduction Data Provided with Requests Running Parsing Code Web Core Database Setup for Initialization Parsing Example Request Line Header Fields Cookies User Name and Password Form Data DSCRIPT Callbacks URLs URL Encoding and Decoding String Commands and Regular Expressions xiii

11 57 Regular Expressions 391 Introduction Regular Expressions in 4D Tips for Working with Regular Expressions Regular Expression Example More Regex Ideas Reusing Existing Code on the Web 393 Introduction Possible Solutions Writing Wrapper Routines Rewriting DOCUMENT TO BLOB 397 Introduction Open Document s Read-Only Mode Reusing Page Elements 399 Introduction Alternatives for Inserting Text Deciding How to Reuse HTML Storing HTML in 4D Managing State 405 Introduction Elements of State-Management Storing State Data Coordinating State Data State Data Expiration Using 4D as an Internet Client 415 Introduction D Internet Commands and ITK Background: TCP/IP Streams Acting as a Web Client Sending and Receiving Uploading and Downloading Files with FTP Ping, Name Lookup, and Other Internet Utilities Feature Reference 63 Web Settings 429 Introduction Summary Connections Web Server Publishing Default HTML Path Mode Settings Security Conversions Cache Memory xiv

12 64 Compiler Requirements Summary 443 Introduction On Web Authentication On Web Connection Methods Called by 4DMETHOD Methods Called by 4DSCRIPT Methods Called by 4DACTION DCGI DIF Variables Used with 4DVAR and 4DHTMLVAR DLOOP DINCLUDE D 6.7 Web Feature Changes Summary 449 Introduction D Web Assistant Picture Commands New and Improved Semi-Dynamic Tags Encryption and Security Commands Web-Specific Commands xv

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Contents. Acknowledgments

Contents. Acknowledgments Contents Acknowledgments Introduction Why Another Book About Web Application Development? How Is This Book Arranged? Intended Audience Do I Need to Start from Scratch? Choosing Development Tools Summary