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Connecting Databases to the Web: Exploring CGI, Java Applets, PHP, and Server Extensions

This document outlines various technologies and architectures for connecting databases to the web, including Common Gateway Interface (CGI), Java Applets, PHP, and Active Server Pages (ASP). It delves into the advantages and disadvantages of each approach, discussing issues such as statelessness, security, and efficiency. Furthermore, the document provides examples of PHP and ColdFusion, illustrating how these technologies can facilitate database access and dynamic web content generation. Perfect for developers seeking insight into web database integration.

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Connecting Databases to the Web: Exploring CGI, Java Applets, PHP, and Server Extensions

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  1. Connecting Databases to the Web

  2. Outline • Common Gateway Interface (CGI) • Java Applets • Server Extensions • PHP • Active Server Pages/ Java Server Pages • What else is out there? • Architectures • Extended PHP example

  3. First Generation Architecture

  4. Second Generation Architecture

  5. Next Generation Architecture

  6. Output Program? Execute Program I/O, Network, DB Common Gateway Interface (CGI) • Some files on server are interpreted as programsdepending on either ext., flag or special directory • Program is invoked and generates MIME header and HTML on stdout Web-Server Web-Server File-System HTTP-Request Load File HTML HTML? HTML-File File

  7. CGI: Discussion Advantages: • Standardized: works for every web-server, browser • Flexible: Any language (C++, Perl, Java, …) can be used Disadvantages: • Statelessness: query-by-query approach • Inefficient: new process forked for every request • Security: CGI programmer is responsible for security • Updates: To update layout, one has to be a programmer

  8. Java-Class Requests Java-Classes Server-Process Execute Applet... Java Virtual Machine (JVM) Java Applets Web-Server Web-Server HTTP-Request Load File File-System HTML-File File Load Applet...

  9. Java Applets: Discussion Advantages: • Platform independent: works for every web-server and browser supporting Java Disadvantages: • Standalone Character: • Entire session runs inside applet • HTML forms are not used • Inefficient: loading can take a long time ... • Resource intensive: Client needs to be state of the art • Restrictive: can only connect to server where applet was loaded from (Java VM but … can be configured) Note: Server-Process can be written in any language

  10. DB Access in Java Java Applet TCP/UDP IP Java-Server-Process JDBC Driver manager JDBC-Driver JDBC-Driver JDBC-Driver Sybase Oracle ...

  11. Server Extensions Previous Approaches • Platform independent and standardized • Simple interface • Lots of programming necessary • Inefficient Server Extensions • Server is extended with handler/module • One handler for all incoming requests • Much more efficient

  12. Script? Output I/O, Network, DB Server Extension Server Extensions: The Basic Idea Web-Server Web-Server HTTP-Request File-System Load File HTML HTML? File HTML-File

  13. Server Extensions • API depends on Server vendor: • Apache Foundation Apache Server: Apache API • Microsoft Internet Information Server: ISAPI • Netscape Enterprise Server: NSAPI • One can define it’s own server extension, e.g. • Authentication module • Counter module

  14. Web-Server File-System HTTP-Request Load File HTML HTML-File ASP-File Output ASP-Script Active Server Page Scripting Engine I/O, Network, DB Active Server Components Active Server Pages • Active Server Pages (ASPs) • Available in Personal Web Server • Based on VBScript, Jscript • Modular Object Model • Active Server Components • Active Data Objects (ADO) for Databaseaccess • In MS .NET ASP+, ADO+ …

  15. Cold Fusion Application Server ODBC-Driver Native Email Directories COM/CORBA DB DB ColdFusion Web-Server Web-Server HTTP-Request Load File File-System HTML HTML? HTML-File File HTML CF Script? Cold Fusion Server Extension

  16. ColdFusion: Simple Query • Proprietary Scripting Language CFML - similar to other scripting languages <CFQUERY NAME=“PersonList” DATASOURCE=“PersonDB”> SELECT * FROM Persons </CFQUERY> <HTML> <BODY> <H1> Person List </H1> <CFOUTPUT QUERY=“PersonList”> <B>Name:</B> #Name# <B>Age:</B> #Age# <B>Salary:</B> $#Sal# <BR> </CFOUTPUT> </BODY> </HTML> <HTML> <BODY> <H1> Person List </H1> <B>Name:</B> Tom <B>Age:</B> 45 <B>Salary:</B> $45000 <BR> <B>Name:</B> Jim <B>Age:</B> 38 <B>Salary:</B> $40000 <BR> <B>Name:</B> Karen <B>Age:</B> 26 <B>Salary:</B> $32000 <BR> </BODY> </HTML>

  17. ColdFusion: Form Handling <CFQUERY NAME=“PersonInfo” DATASOURCE=“PersonDB”> SELECT * FROM Persons WHERE Name=#Form.PName# </CFQUERY> <HTML> <BODY> <CFOUTPUT QUERY=“PersonInfo”> <H1>#Name#</H1> <UL> <LI><B>Age=</B> #Age# <LI><B>Salary=</B> $#Sal# <LI><A href=“#URL#”><B>Homepage</B> </A> </UL> </CFOUTPUT> </BODY> </HTML> <HTML> <BODY> <H1>Tom </H1> <UL> <LI><B>Age:</B> 45 <LI><B>Salary:</B> $45000 <LI><A HREF=“www.tom.com” <B>Homepage</B></A> </UL> </BODY> </HTML> <HTML> <BODY> <FORM ACTION="http://www.abc.com/cf/pf.cfm"> <H1> Find Person </H1> Person Name <INPUT NAME="PNAME"> <p> <INPUT TYPE="submit" VALUE="Find"> </FORM> </BODY> </HTML>

  18. ColdFusion: Misc. Issues • Site admin sets up data sources very similar to the handling of ODBC data sources in MS Windows • In fact ColdFusion combines techniques to access databases: • Generation ofHTML code • Java Applets embedded via <CFGRID></CFGRID> access the database through the application server • Application server is also gateway to database for the ColdFusion IDE (ColdFusion Studio)

  19. PHP How does PHP differ from ASP and CF? • Free, open source • Many client libraries integrated • Runs on any web server supporting CGIs (MS Windows or Unix) • Module version for Apache Web-Server Web-Server File-System HTTP-Request Load File HTML HTML-File PHP-File Output PHP-Script PHP Module Database APIs, other APIs SNMP, IMAP, POP3, LDAP, ...

  20. PHP: A Simple Example <HTML> <BODY> <?PHP $db = mysql_connect("localhost", "dbuser"); mysql_select_db("mydb",$db); $result = mysql_query("SELECT * FROM employees",$db); ?> <TABLE BORDER=1> <TR><TD>NAME</TD><TD>POSITION</TR> <?PHP while ($myrow = mysql_fetch_row($result)) { printf("<tr><td>%s %s</td><td>%s</td></tr>\n", $myrow[1], $myrow[2], $myrow[3]); } ?> </TABLE> </BODY> </HTML>

  21. PHP: Misc Issues • Syntax Perl/C like • Form fields are available as variables in following page • has e.g. image and PDF generation on the fly • some OO features (e.g. classes) • The number of functions is steadily increasing

  22. Java Server Pages

  23. JSP Example—Hello.jsp <html> <head> <title>My first JSP page </title> </head> <body> <%@ page language=”java” %> <% System.out.println(“Hello World”); %> </body> </html>

  24. And the Output IS <html> <head> <title>My first JSP page </title> </head> <body> Hello World </body> </html>

  25. What Else Is Out There? • Java Server Pages (JSP) • similar to PHP • Java Servlets • very similar to CGIs • A couple of solutions from Oracle • PENN ExpressApp is based on OWS • various web shop applications • all of them use a more or less sophisticated scripting language • and a lot more ...

  26. Databases Usually Used • ASP • MS Jet Engine (DB engine behind MS Access) • MS SQL Server • Oracle (ODBC) • ColdFusion • Oracle (native driver support) • Informix (native driver support) • Sybase (native driver support) • PHP • MySQL (linked in client library) • mSQL (linked in client library) • Postgres (linked in client library) • Oracle (linked in client library)

  27. Architectures • The architecture type depends on kind and number of servers involved • Different archictures different advantages and disadvantages • Generally we can distinguish between different types: • 2-tier architecture • 3-tier architecture • n-tier architecture • What matters: SPEED

  28. HTTP-Request HTML-File 2-tier Architecture • Web server plus module connecting to database, LDAP, IMAP, ... 1 Web-Server Module 2 DB Directory Mail Server SNMP

  29. 2-tier Architecture • Advantages: • easy and fast to setup • easy to administrate • Disadvantages: • not fail safe (single point of failure) • scales badly on high loads

  30. 3-tier Architecture • Web server plus application server connecting to database, IMAP, ... 1 Web Server [Cluster] Application Server [Cluster] 2 Other Servers [Cluster] 3 DBRepl. DB DB Mail Server SNMP

  31. 3-tier Architecture • Advantages: • better scalabilty • more reliable through failover mechanisms • offers better load balancing • Disadvantages: • complicated to set up an maintain

  32. Architectures: Usage • 2-tier • Apache-PHP plus Database etc. • 3-tier • ColdFusion 4.x, BEA Weblogic • Oracle Web Application Server? • n-tier • big sites with custom systemslike Yahoo, Amazon.com, eBay Classification not always 100%

  33. Technology Choices • PHP/{Oracle|mySQL} • ASP/Access/ODBC -- Need MS IIS • JSP/{Oracle|mySQL}/JDBC -- Need Tomcat or Apache+JServ • Any Other Choices?

  34. Extended PHP Example

  35. Extended PHP Example

  36. Plain HTML <HTML> <TITLE>Simple SQL Web Interface for Movie Table</TITLE> <BODY> <H1>Simple SQL Web Interface for Movie Table</H1> [PHP code here] <FORM ACTION="query.php3" METHOD=GET ENCTYPE="TEXT/PLAIN"> <INPUT SIZE=100 MAXLENGTH=250 NAME="query" VALUE="select title, year, mid from movies"> </FORM> </BODY> </HTML>

  37. Table Generation (Part 1) <?php /* check for query, if empty describe movies */ if (!isset($query)) { $query = "describe movies"; } else { $query = stripslashes($query); print "<B>Your query: </B>\"" . $query . "\"\n"; } $result = mysql_query($query, $conID) or die ("Invalid query"); // disable error reporting $eLevel = error_reporting(0); ?>

  38. Table Generation (Part 2) <?php /* generate table header or catch INSERT, DELETE and UPDATE statements */ if (mysql_affected_rows($conID) > 0) print "<B>affected " . mysql_affected_rows($conID) . " row(s)!</B><P>\n"; if (mysql_num_rows($result) > 0) { $noFields = mysql_num_fields($result); print "<table border=\"1\">\n<tr>\n"; for ($i = 0; $i < $noFields; $i++) print "<th><b>" . mysql_field_name($result, $i) . "</b></th>\n"; print "</tr>\n"; while ($row = mysql_fetch_array ($result)) { print "<tr>\n"; for ($i = 0; $i < $noFields; $i++) print "<td>&nbsp;" . $row[$i] . "&nbsp;</td>\n"; print "</tr>\n"; } print "</table>\n"; } ?>

  39. Links • Software: • Apache: http://www.apache.org/ • ASP: http://msdn.microsoft.com/workshop/server/default.asp • ColdFusion: http://www.allaire.com/coldfusion/ • MySQL: http://www.mysql.com/ • Oracle: http://www.oracle.com/ • Oracle Technet: http://technet.oracle.com/ • PHP: http://www.php.net/, http://www.zend.com/ • Others: • c|net: http://www.builder.com/ • DevShed: http://www.devshed.com/Server_Side/ • Webmonkey: http://www.webmonkey.com/

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