2. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS eCommerce Technology 20-751 Lecture 4: Web Architecture

3. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Two-Tier Architecture SOURCE: FOURNIER TIER 1: CLIENT TIER 2: SERVER Server performs all processing Web Server Application Server Database Server This architecture is deprecated. Server does too much work.

4. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Three-Tier Architecture TIER 1: CLIENT TIER 2: SERVER TIER 3: BACKEND Application server offloads processing to tier 3 SOURCE: FOURNIER Web Server + Application Server Note: Using 2 computers instead of 1 can result in a huge increase in simultaneous clients. Depends on % of CPU time spent on database access.

5. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS N-Tier Architecture SOURCE: FOURNIER Achieves full separation of function and administration Huge number of simultaneous clients Managed and tuned by DBA Optimized for web page delivery Coded for specific application

6. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS InterShop Architecture SOURCE: INTERSHOP

7. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Connecting to Legacy Systems by “Wrapping” Web App Web Server Legacy App MAINFRAME “WRAPPER” Wrapper Middleware

8. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Connecting to Legacy Systems The “screen scraper” Client Web server Legacy database Terminal screen data Screen scraper Existing application HTML data Legacy system (mainframe) SOURCE: WIM GEVERS

9. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Screen Scraping Some systems produce as their only output commands to 80 x 24 display terminals Sequences of characters telling the terminal to move its cursor and display data, e.g. ^M0238Jan. ^M024416, ^M02482000 displays “Jan. 16, 2000” in row 2, starting at col. 38 Screen scraping involves virtual simulation of the display terminal to retrieve the data Vendors –Intelligent EnvironmentsIntelligent Environments

10. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Web Broker Architecture SOURCE: INTERWORLD FEATURES More distributed than InterShop Broker acts as distribution agent TIER 1 TIER 2 TIER 3 TIER 4

11. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Server Accelerators (Surrogates) Origin Server Client A Server Accelerator (surrogate) all content requests for the origin server requests to origin server Client B maintains cache of frequently accessed web pages SOURCE: G. TOMLINSONG. TOMLINSON

12. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Server Clusters (Farms) REPLICATED CONTENT EACH REQUEST SENT TO A FREE SERVER

13. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Server Clusters (Farms) Origin Server A Client Surrogate Client’s content request. Origin Server B Origin Server C Origin Server n Surrogate Request- Router Surrogate 1 2 3 Response indicates best surrogate. Client connects to best Surrogate for content. 1. 2. 3. SOURCE: G. TOMLINSONG. TOMLINSON

14. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Server Clusters (using DNS) SOURCE: NOVELLNOVELL MULTIPLE SURROGATES Surrogate

15. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Today’s Storage Architecture LAN Channels Servers Storage Clients BACKUP SOURCE: UNISYS

16. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Storage-Area Network (SAN) Solution LAN SAN Servers Storage Clients BACKUP OR REPLICATION SOURCE: UNISYS

17. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS SAN Definition Multiple paths to each resource Any-to-any connections Global Address view Open structure using industry standard protocol No node dependencies, (can function even if one or more nodes are inoperative) Optimized for large block transfers High bandwidth and high availability Scales up with no performance loss SOURCE: UNISYS

18. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Applets: Mobile Internet Code SOURCE: FOURNIER HTML: code=clock.class codebase=“http://www.sun.com/classes”

19. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS What Applets Can’t Do Reference specified area of memory Access local file system Execute other programs Load local libraries Create or manage threads in others Connect to other hosts except originator Open windows Applets identify themselves through code signing (digital signature) SOURCE: POSTECH

20. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Java 2 Security Model SOURCE: SUN MICROSYSTEMS Applications are identified by digital signatures Range of security policies Domain = Set of classes given the same permissions Untrusted foreign applets run here Security manager controls access to system resources Trusted native applications run here Every application is subject to a security policy

21. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Java Beans Java Beans : reusable software components containing business logic for manipulation in a visual builder tool (e.g. Borland JBuilder, IBM Visual Age for Java) Write once, run anywhere (WORA) Properties of Beans: –Introspection: builder tool can analyze how a Bean works. getBeanInfo(BeanClass) –Customization: developer can use an app builder tool to customize the appearance and behavior of a Bean –Events: enables Beans to communicate and connect together –Properties: property editors to customize Beans –Persistence: developers can customize Beans, store and retrieve them, with customized features intact, for future use Can buy and sell Beans. Visit Sun.Sun

22. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Enterprise Java Beans (EJB) An interface specification for building scalable, distributed, component-based, multi-tier enterprise- wide applications Java Beans for server-side business applications Platform and vendor-neutral Java Beans extended with –transaction processing –state management –services not offered by the Java Virtual Machine Idea: incorporate data and business logic into objects in one place in the enterprise Employ reusable components

23. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Enterprise Java Beans SOURCE: SUN MICROSYSTEMS SERVER MANAGES EJB CONTAINERS CONTAINER HANDLES: TRANSACTION MGMT SECURITY CLIENT CONNECTIVITY LIFE CYCLE MGMT ENTERPRISE BEANS HANDLE BUSINESS LOGIC

24. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Enterprise Java Beans SOURCE: SUN MICROSYSTEMS SESSION BEAN PERFORMS TASK FOR 1 CLIENT IS NOT PERSISTENT ENTITY BEAN REPRESENTS BUSINESS ENTITY OBJECT SHARED BY MANY CLIENTS IS PERSISTENT SESSION BEAN CLIENT CUSTOMER ON WEB SERVLET RESPONDS TO CART APPLET DATABASE STORES ENTITY BEAN STATES

25. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Java Server Pages (JSP) Delivering customized content SOURCE: SUN

26. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS JSP Page Example <jsp:useBean id=“clock” class=“calendar.JspCalendar”/> Day of Month: is Year: is SOURCE: SUN Page invokes a Java bean from a servlet (Similar to an applet) Page invokes methods on the servlet to generate dynamic content Looks like an HTML page

27. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Major Ideas Three-tiered (n-tiered) architecture Web development tools Storage Area Networks Enterprise Java Beans

28. 20-751 ECOMMERCE TECHNOLOGY SUMMER 2002 COPYRIGHT © 2002 MICHAEL I. SHAMOS Q A &