Visual FoxPro Database Publishing on the Internet

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Visual FoxProDatabase Publishing on the Internet

• by Rick Strahl
• West Wind Technologies
• http//www.west-wind.com/

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Internet Development

• Businesses are expanding their operations onto
  the Internet
• Internet Development is exploding
• Active, Database Applications are in high demand

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Why build Web Applications?Issues that make the
Web hot

• Distribute widely
• Administer centrally
• Universal Client Interface
• Application Platform of the future

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Limitations of Web ApplicationsOr Two steps
forward, one step back...

• Configuration issues
• Interface limitations of HTML
• Indirect data accesss through server
• Mostly non-visual development
• Server based programming model

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• Browser provides the Active interface
• Web Server provides data / application
  connectivity
• The Internet Server API (ISAPI) is the building
  block for server side extensions

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How the Active Web Works
Server side
Client side
Active Documents
Webserver
Static HTML Pages
Web Browser Displays HTML
HTTP
Server Extensions ISAPI/CGI
ActiveX Controls/ Java
Browser Scripting VBScript JavaScript
Dynamic Data and Database
TheWall
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Common Gateway InterfaceTraditional Web Interface
CGI.exe (1) (EXE, CMD, BAT)
CGI.exe (n) (EXE, CMD, BAT)
CGI.exe (2) (EXE, CMD, BAT)
New system process for each instance of
script. (relatively slow, resource intensive)
Web Server HREF/cgi-bin/cgi.exe?Parms
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Internet Server API (ISAPI)Extending the
Architecture within the Server
Web Server HREF/scripts/isapi.dll?parms
MyISAPI (1,2..n) (Multithreaded, In-Process DLL)
OtherISAPI (Multithreaded, In-Process DLL)
Loads DLL once after which it stays resident,
processing multiple requests simultaneously.
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Internet Server API (ISAPI) The extension
interface for IIS
Static content (e.g., HTML)
Microsoft Exchange
Databases (FoxPro, SQL, Access etc.)
Custom scripts, Interfaces to other applications
etc.
ODBC
MAPI
Internet Database Connector
Active Server Pages (Denali)
Exchange Web Connector
Custom ISAPI Scripting
ISAPI
Microsoft Internet Information Server
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Getting StartedWhat you need for building Web
apps

• Fast Pentium box (133Mhz/32-64megs)
• WindowsNT (recommended)
• Web Server
• Connector Interface/Application
• Web browser
• Basic HTML skills
• Everything can run on 1 box!

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Connecting Visual FoxPro DataSome of the tools
available for IIS

• Active Server Pages (IIS 3.0)
• FoxISAPI connector (OLE)
• West Wind Web Connection (ISAPI/OLE)

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Active Server Pages (IIS 3.0)Server side
scripting for IIS

• Object Based Architecture
• Tight integration with IIS
• Database Connectivity with Active Data Objects
  (ADO)
• Supports external object creation
• Several sophisticated objects are built-in

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Active Server ArchitectureComponents Galore
Response/Request Objects (Input and Output)
Server Object (System Services)
ASP.DLL (ISAPI Extension)
Scripting Engine (VBScript/JavaScript)
Active Data Objects (ODBC)
Session/Application Objects (Keeping State)
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Active Data Objects

• Lightweight ODBC Connector
• Implements OLE DB (ODBC 3.5)
• Based on Visual Basics Remote Data Object
• Its fast especially when tied to a persistent
  connection object!
• Implemented as Automation Object.

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Automation Server Access
OLE EXE Server (OutOf Process) TClassTmethod(
)
ASP Scripting Engine HTML containing VBScript
code
Creates Object Reference lt oServerServer.CREATE
OBJ(Tserver.TClass) cVaroServer.Tmethod(Par
m1,1) gt

Web Server
ADO Data Object (ODBC Data Access)
OLE DLL Server (InProcess)

HREFMyPage.ASP
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Active Server Summary

• Pros
• Tight Integration with IIS
• No hassle configuration
• Very easy for simple active content
• Cons
• Code Management
• Automation Server Scalability
• Scripting Language Limitations

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FoxISAPIConnecting VFP Automation servers

• Direct link from Web pages
• ISAPI DLL creates persistent Automation object
• DLL does equivalent of
• Passes form vars in parameter
• Passes server vars in INI file

oServerCREATEOBJECT(TOleServer.TOleClass) oServ
er.YourMethod(UserId1,c\temp\fox2.ini)
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How FoxISAPI works
Visual FoxPro OLE Server (loaded once then stays
in memory)
Method1
Method2
Methodn
returns HTML Document
passes HTML Form Data
Web Server
FOXISAPI.DLL (HREFfoxisapi.dll/Server.Class.Meth
od) multithreaded/running InProcess
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Hello World with FoxISAPI
HREF/scripts/foxisapi.dll/TDevCon.TFoxIsapi.Hell
oworld?
DEFINE CLASS TFoxISAPI AS Custom
OLEPUBLIC FUNCTION Helloworld LPARAMETER
lcFormVars, lcIniFile, lnReleaseFlag LOCAL
lcOutput DEFINE CR CHR(13)CHR(10) HTTP
header - REQUIRED on each request! System
Defines lcOutput"HTTP/1.0 200 OK"CR
"Content-type text/html"CRCR lcOutputlcOutput
"ltHTMLgtltBODYgt"CR "ltH1gtHello World from
Visual FoxProlt/H1gtltHRgt"CR "This page was
generated by Visual FoxPro...ltHRgt"CR "lt/HTMLgtlt/
BODYgt" RETURN lcOutput ENDDEFINE
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FoxISAPI Method Rules

• Must take 3 parameters
• lcFormVar - HTML Form vars or parameters passed
  on the URL
• lcIniFile - filename containing server var
• lnReleaseFlag - Set to keep or release server
  reference.
• Must return HTTP compliant output
• HTML document including HTTP header
• Use custom HTTP headers for things like
  authentication, redirection, Cookies etc.

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Set up for FoxISAPI

• OLE Server must be registered
• Copy FoxISAPI.dll into script dir
• Directory must have Web Server Execute rights
  set!
• Run DCOMCnfg on NT 4.0
• Add IUSR_ account to default rights
• Set user to Interactive user on the specific
  server
• Need to re-run whenever server is rebuilt

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FoxISAPI OLE Instancing

• InProcess DLL
• Very fast
• Only 1 VFP server can be InProcess
• MultiUse (Out of Process EXE)
• Slightly slower
• Multiple different servers
• Single Use
• Use for multiple pooled servers
• Same server can be instanced more than once

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Starter FoxISAPI classProvided on the CD

• Send/SendLn() Send text to output
• StandardPage() Generates a full HTML page
• ContentTypeHeader() Adds HTTP header
• StartRequest() Called to set up a request.
  Decodes input vars and clears the
  output property.
• GetFormVar() Retrieves a form variable
  passed in with the first parameter.
• GetCGIVar() Retrieves a server/browser
  variable from the INI file.
• ReleaseServer() Standard method that releases
  the OLE server.

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Method example with FoxISAPI class
HREF/scripts/foxisapi.dll/TDevCon.TFoxIsapi.Test
Method?
TFoxISAPI TestMethod FUNCTION
TestMethod LPARAMETER lcFormVars, lcIniFile,
lnReleaseFlag LOCAL lcOutput, lcUserId,
lcName Decode the Form Vars and assign INI
file to class property THIS.StartRequest(lcFormVar
s,lcIniFile) Must always add a content Type
Header to output first THIS.HTMLContentTypeHeader(
) lcUserIdTHIS.GetFormVar("UserId") lcNameTHIS.
GetFormVar("UserName") THIS.SendLn("ltHTMLgtltBODYgt"
) THIS.SendLn("ltH1gtHello World from Visual
FoxProlt/H1gtltHRgt") THIS.SendLn("The current time
is "time()"ltpgt") THIS.SendLn("ltbgtEncoded
Form/URL variableslt/bgt "lcFormVars"ltBRgt") THIS.
SendLn("ltbgtDecoded UserIdlt/bgt "
lcUserId"ltpgt") THIS.SendLn(To retrieve the
Browser use THIS.GetCGIVar("HT
TP_USER_AGENT","ALL_HTTP")
THIS.GetCGIVar("HTTP_USER_AGENT","ALL_HTTP")
) THIS.SendLn("ltHRgtlt/HTMLgtlt/BODYgt") RETURN
THIS.cOutput
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FoxISAPI Summary
Pros Full support for Visual FoxPro Real
Development Environment Excellent
performance Cons Difficult First Time
Configuration No Web specific code
support Doesnt run on non-ISAPI servers or
Windows 95
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West Wind Web Connection

• Extensive Visual FoxPro framework for Web
  development
• Support for multiple sessions
• Works with Automation and File based messaging
  interchangeably
• Scalable across multiple machines
• Real-time, live debugging
• Server Management

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Web Connection Data Server
WebServer
Visual FoxPro Data Server (already loaded)
wc.dll (ISAPI)
Server and Form Data
returns HTML Doc
HTML Link
FoxPro User Code
Scripted HTML
HTML Document
Web Browser
Database
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How your code gets called
wwServer Visual FoxPro form class handles
request routing on incoming requests.
wwServerProcess() Routes request to your PRG
file
invokes
MyPRG creates new Process object and calls
Process method
To process this URL wc.dll?MyPRGMyMethod
CGIProcess Class Contains MyMethod() that creates
HTML output. Class can contain multiple methods.
Returns HTML object
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How your code gets called
DEFINE CLASS MyProcess... Procedure
Process loCGITHIS.oCGI lcParamloCGI.GetParam(1)
Any global processing here Check for
Cookies, User Ids etc. Route to appropriate
method CASE PEMSTATUS(THIS,lcParam,5)
EVAL("THIS."lcParam"()") RETURN PROCEDURE
CUSTLIST ltYour processing goes heregt ltCreate
HTML document filegt RETURN
wwServer Visual FoxPro form thats
an OLEPUBLIC Automation Object or uses a timer to
poll for requests on disk.
Creates Process Object
returns HTML object
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Web Connection FrameworkSome of the features
available

• Class framework for easy access to CGI/HTML
  functionality
• Solid error handling scheme
• Hit Logging, Mulitple Session Management and
  Maintainence Routines
• HTML scripting from files or memos
• Single method output of tables to HTML
• Built-in support for many advanced HTML/HTTP
  features

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Sample Processing Code
wwCGIProcess CustList FUNCTION
CustList loCGITHIS.oCGI loHTMLTHIS.oHTML lcClie
ntTRIM(UPPER(loCGI.GetFormVar(Client)) SELECT
tt_cust.company FROM TT_CUST WHERE
UPPER(tt_cust.company)lcClient INTO CURSOR
TQUERY ORDER BY company,Datein IF _TALLYlt1
THIS.ErrorMsg("No Matching Records found...")
RETURN ENDIF HTML output creation
follows loHTML.HTMLHeader("NWDS Customer List",
"Customer List
Sample",FFFFFF) loHTML.EnclosedText("H3","Time
review for "lcClient) loHTML.SendLn(ltpgt)
Now show the table loHTML.ShowCursor() loHTML.HT
MLFooter() RETURN
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Tools summary

• Check out Active Server for sophisticated server
  scripting and connectivity to VFP via Auto
  servers
• For more control use Visual FoxPro as a Web data
  server
• FoxISAPI provides powerful OLE connectivity with
  an easy interface
• For a complete Fox based Web environment check
  out Web Connection

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