1. Chapter 4: Core Web Technologies

2. Contents - Chapter 1 Exchanging information over the Internet
HTTP, HTML
URI, URI
Web server, web browser
Web services for supporting remote clients
Applets
Common Gateway Interface (CGI)
Servlets
Application servers
Middleware for Web applications
J2EE
Web technologies for application integration
Middleware extensions
Firewalls and tunneling

3. Before and after the web
Early protocols, applications
Telnet: to log in to a remote machine
SMTP: Simple Mail Transfer Protocol
FTP: File Transfer Protocol
Archie: FTP to create a distributed file system
Gopher: GUI for publishing and accessing text files over the Internet
Web technologies
Web server
Web browser
HTTP: HyperText Transfer Protocol
HTML: HyperText Markup Language
URI: Uniform Resource Identifier
URL: Uniform Resource Locator

4. wide area network (Internet)
Proxy
HTTP tunnel
firewall
firewall
HTTP
client
HTTP
proxy
HTTP
gateway
HTTP
server
wide area network (Internet)
Acts as a server and client
Caching
Block undesired sites
Log usage
Bypass blocks
Scan outgoing traffic

5. wide area network (Internet)
Gateway
HTTP tunnel
firewall
firewall
HTTP
client
HTTP
proxy
HTTP
gateway
HTTP
server
wide area network (Internet)
Acts as an intermediary for a server
Keeps machines anonymous
Controls access to the network
Performs load-balancing, authentication, decryption

6. wide area network (Internet)
Firewall
HTTP tunnel
firewall
firewall
HTTP
client
HTTP
proxy
HTTP
gateway
HTTP
server
wide area network (Internet)
Blocks unauthorized access, permits authorized communications
permit / deny / encrypt / decrypt / proxy all computer traffic between different security domains

7. wide area network (Internet)
Tunnel
HTTP tunnel
firewall
firewall
HTTP
client
HTTP
proxy
HTTP
gateway
HTTP
server
wide area network (Internet)
Acts as a blind relay between two connections
Encapsulate protocols within HTTP or SSH (Secure Shell) to get through what the firewall would prevent

8. Secure Socket Layer (SSL)
HTTPS
client
HTTPS
server
application layer
network layer
Secure Sockets Layer (SSL)
TCP/IP
Normally HTTP traffic is not encrypted, it can be “sniffed”
SSL uses public key encryption
HTTPS: HyperText Transfer Protocol over Secure sockets layer
HTTP “cookies” are used to store data on the client machine

9. A 3-tier architecture on the web
client
client
HTTP
server
HTTP
client
wide area network (Internet)
middleware
“Let’s put an ATM” in every home”
Business-to-consumer (B2C) interaction
The web browser is a universal client
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

10. Applets firewall wide area network (Internet) middleware Web server
client
applet
java virtual machine
browser
wide area network (Internet)
HTTP is a document exchange protocol, it’s static
Applets are downloadable programs
The server sends the appropriate program each time
The web browser becomes a universal client
Code must be small for rapid transfer
middleware
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

11. Common Gateway Interface
HTTP GET
request
Web server
browser
firewall
client
CGI program
wide area network (Internet)
middleware
The CGI program is on the server and it has a URL
When the URL is accessed, the CGI program is executed and its output is saved as an HTML document
This saved document is returned to the web browser which then displays it
It is possible to pass parameters to CGI programs
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

12. Servlets firewall HTTP GET request wide area network (Internet)
Web server
Java server process
HTTP GET
request
firewall
browser
Java thread
client
Similar to CGI, but “lightweight”
Run as Java threads
Saves the cost of context switching
Memory efficient
Can be stateless
wide area network (Internet)
middleware
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

13. Application servers CHAPTER 2 FIGURE 2 -section 1.2 firewall
other protocols
client
other servers ( , SOAP,..)
Web server
browser
HTTP
firewall
presentation layer
It’s a middleware platform that provides support for Web access
Covers both the application logic and the presentation layer
Prepares, dynamically generates, manages document
wide area network (Internet)
application logic layer
connection to resource mgmt layer
CHAPTER 2
FIGURE 2 -section 1.2
application server
resource management layer
Copyright Springer Verlag Berlin Heidelberg 2004

14. J2EE – main components support for communication and presentation
Servlets
JavaServer Pages (JSP)
Java API for XML Processing (JAXP)
JavaMail
support for communication and presentation
Java Authentication and Authorization Service (JAAS)
Enterprise Java Beans (EJB)
Java transaction API (JTA)
support for the application integration
Java Message Service (JMS)
Java Naming and Directory Interface (JNDI)
Java DataBase Connectivity (JDBC)
Java 2 Connector Architecture (J2CA)
support for access to resource managers
Copyright Springer Verlag Berlin Heidelberg 2004

15. presentation layer application logic layer
EJB
EJB
EJB
(load balancing, pooling, caching, transaction, persistence,…)
services
EJB container
(management and security)
administration
JNDI
JMS
JDBC
J2CA resource adapter
J2CA resource adapter
other adapters
application server
DBMS applications
enterprise system 1
enterprise system 2
enterprise system n
Copyright Springer Verlag Berlin Heidelberg 2004

16. application logic layer
client
servers for other connections (e.g., WAP)
server
Web server
multidevice content delivery
(load balancing, pooling, caching,…)
services
Servlets
JSPs
XML support
Web services support
(management and security)
administration
personalization logic
presentation layer
application logic layer
connection to resource mgmt layer
application server
resource management layer
Copyright Springer Verlag Berlin Heidelberg 2004

17. Possible ways to connect
client
client
middleware
wide area network (Internet)
middleware
server
(resource manager)
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

18. Direct integration of middleware platforms
client
client
middleware
middleware
remote-middleware
protocol
remote-middleware
protocol
WAN communication
protocol
wide area network (Internet)
WAN communication
protocol
server
(resource manager)
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

19. wide area network (Internet)
HTTP tunnel
firewall
firewall
client
Web server
Web server
client
wide area network (Internet)
middleware
middleware
remote-middleware
protocol
remote-middleware
protocol
WAN communication
protocol
WAN communication
protocol
server
(resource manager)
server
(resource manager)
Copyright Springer Verlag Berlin Heidelberg 2004

20. Summary Decades of accumulated knowledge on multi-tier architectures
Use the same technology over the Internet
The client can be on
A Local Area Network (LAN)
Over the Internet
Architectural implications and design constraints from using the Web are important