1 connecting databases to the web october 30 th, 2001 xinguang sheng marcus haebler

1

Connecting Databases to the Web

October 30th , 2001

Xinguang Sheng

Marcus Haebler

Connecting Databases to the Web 2

Outline

• How Does Web application architecture evolves

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


First Generation Architecture


Second Generation Architecture


Next Generation Architecture


• 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

Common Gateway Interface (CGI)

HTTP-Request

HTML-File

Web-Server

File-SystemLoad File

FileHTML?

HTML

Execute Program

Program?Output

I/O, Network, DB


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

CGI: Discussion


Java Applets

Web-ServerHTTP-Request

HTML-File

Web-Server

File-System

Load File

FileLoad Applet...

Java-Class Requests

Java-Classes

Execute Applet...

Java Virtual Machine (JVM)

Server-Process


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

Java Applets: Discussion


Java-Server-Process

DB Access in Java

Sybase

Java Applet

TCP/UDP

IP

Oracle ...

JDBC-Driver

JDBC-Driver

JDBC-Driver

JDBC Driver manager


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

Server Extensions


Server Extensions: The Basic Idea

File-SystemWeb-Server

HTTP-Request

HTML-File

Web-Server

Load File

FileHTML?

HTML

I/O, Network, DB

Script?Output

Server Extension


• 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

Server Extensions


• Active Server Pages (ASPs)- Available in IIS and Personal Web

Server- Based on VBScript, Jscript- Modular Object Model- Active Server Components- Active Data Objects

(ADO) for Databaseaccess

- In MS .NET ASP+, ADO+ …

Active Server Pages


HTTP-Request

HTML-File

Load File

ASP-File

HTML

ASP-ScriptOutput

I/O, Network, DBActive Server Page

Scripting Engine

Active Server Components


ColdFusion


HTTP-Request

HTML-File

Web-Server

Load File

FileHTML?

HTML

CF Script?HTML

Cold Fusion Server Extension

Cold Fusion Application Server

ODBC-Driver Native

DB DB

Email

Directories

COM/CORBA


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>


ColdFusion: Form Handling

<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>

<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>

<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>


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 of HTML 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)


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


HTTP-Request

HTML-File

Load File

PHP-File

HTML

PHP-ScriptOutput

Database APIs,

other APIs SNMP,

IMAP, POP3,

LDAP, ...

PHP

Module

Web-Server


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>


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)• Version 3 installed on fling.seas.upenn.edu• Version 4.0.2 latest version (zend engine)

- more OO features- is based on a different, faster scripting engine- more modular architecture

• The number of functions is steadily increasing


Java Server Pages


JSP Example—Hello.jsp

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


And the Output IS

<html> <head> <title>My first JSP page </title> </head> <body> Hello World</body> </html>


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 ...


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)


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


Web-Server

2-tier Architecture

• Web server plus module connecting to database, LDAP, IMAP, ...

HTTP-Request

HTML-File

Module

DB Directory

Mail Server

SNMP

1

2


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


3-tier Architecture

• Web server plus application server connecting to database, IMAP, ...

DB DB Mail Server

SNMP

1

3

2

Web Server [Cluster]

Application Server [Cluster]

Other Servers [Cluster]

DBRepl.


3-tier Architecture

• Advantages:- better scalabilty- more reliable through failover mechanisms- offers better load balancing

• Disadvantages:- complicated to set up an maintain


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 systems

like Yahoo, Amazon.com, eBay

Classification not always 100%


Technology Choices

• PHP/{Oracle|mySQL} – Minimum Setup use fling or Eniac.

• ASP/Access/ODBC -- Need MS IIS• JSP/{Oracle|mySQL}/JDBC -- Need

Tcomcat or Apache+JServ• Any Other Choices?


Extended PHP Example browser

http://localhost/query.php3


Extended PHP Example browser



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>

browser



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);

?>

browser



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> " . $row[$i] . " </td>\n";print "</tr>\n";

} print "</table>\n";

}?>

browser



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/

1 connecting databases to the web october 30 th, 2001 xinguang sheng marcus haebler

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