An Overview of Architectures for Web-Based Application Systems Instructor: Dr. Jerry Gao San Jose State University URL:

Topic: An Overview of Architectures for Web-Based Application Systems - ( ) Hypertext Web Systems: Graphic Web Browsers + Hyperlinks + HTML files. Features:HTML-based thin client. Limited Server Functions. Application: Only for documentation sharing and accesses. Static Web Site construction. Pros:Simple and easy to set up. Cons: Very server processing functions No dynamic HTML generation. No support for user interaction Not easy to maintain and manage Browser user client Internet/Intranet HTTP Server HTML Files URL HTTP HTML Jerry Gao Ph.D.5/1999

- ( ) Interactive HTML-based Web Systems: Graphic Web Browsers + Hyperlinks + HTML files Plus: Forms, Tables, CGI, and Secured Transactions: SSL, S-HTTP, Firewalls Features:Supporting user interactions and requests HTML-based client, CGI-based Server program Secured communications and transactions Applications: DHTML web sites, Banking, On-line systems Pros:Secured communications. Dynamic HTML generation. User friendly due to user interactions. Cons:Slow speed, limited client functions and GUI support. Unstructured server programs with low concurrence Browser user client Internet Web Server HTML Forms HTML Tables Firewall Gateway Programs CGI HTML & Forms S-HHTP/SSL Database Server Jerry Gao Ph.D.5/1999 Topic: An Overview of Architectures for Web-Based Application Systems

- ( ) Complex Interactive Web Systems(a): Client: Web Browser + HTML + JavaScript, Server: Web Server + CGI + Gateway Programs + Database Server Plus secured transaction based on secured protocol and firewalls Features:Supporting better user interactions and requests HTML/JavaScript client, CGI-based Server program Secured communications and transactions Applications: Web-base application systems, tools, group-ware, On-line systems Pros:Global accesses, platform independent. Secured communication and transactions. Have a better GUI interface due to JavaScript features. Cons:Limited support for graphics and window applications Unstructured server programs with low concurrence Browser user client Internet Web Server HTML Forms HTML Tables Firewall Gateway Programs CGI HTML Forms + JavaScript Database Server Database HTTPS or SSL (a) Tier 1Tier 3Tier 2 Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Complex Interactive Web Systems(b): Client: Web Browser + HTML + JavaScript, Server: Web Server + Java Servlet + Database Server Plus secured transaction based on secured protocol and firewalls Features:Supporting better user interactions and requests HTML/JavaScript client, Java Servlet-based communication gateway Secured communications and transactions Applications: Web-base application systems, tools, group-ware, On-line systems Pros:Global accesses, platform independent. Secured communication and transactions. Have a better GUI interface due to JavaScript features. Cons:Limited support for graphics and window applications. Unstructured server programs with low concurrence. Browser user client Internet Web Server Firewall Java Servlet HTML Forms + JavaScript Database Server Database HTTPS or SSL (b) Tier 1Tier 3Tier 2 Application Server HTML Forms HTML Tables Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Complex Interactive Web-Based Systems (c): Client: Web Browser + HTML + Java Applets Server: Web Server + CGI (Gateway Programs) + Database Server Plussecured transaction based on secured protocol & firewalls Features:Supporting complex user interactions and requests HTML/JAVA client, CGI-based Server program Secured communications and transactions Applications: Web-base application systems, tools, group-ware, On-line systems Pros:Global accesses, platform independent. Secured communication and transactions. Supporting Complex GUI interface. Cons:Slow speed on Java applet download, and more system resources. Unstructured server programs with low concurrency. Browser user client Internet/Intranet Web Server HTML Forms HTML Tables Firewall Gateway Programs CGI HTML Forms + Java Applets Database Server Database HTTPS or SSL (c) Tier 3 Tier 2Tier 1 Application Server Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Object Web Systems: (a) Java Web: Java Applets + Mobile Components (RMI) Client:Browser, Java Applets + RMI server stub. Server:RMI server, Application server and DB server. Features:Supporting complex user interactions and requests RMI communications between clients and server No standard communication protocols. Java Client and Server. Applications: Intranet Web-base application systems, tools, group-ware. Pros:Intranet accesses, platform independent. Support multithreading server. Supporting Complex GUI interface. Cons:No secured communications. Client and server must be written in Java. Limitation on providing scalable servers. Internet/Intranet Server StubJava ClientClient Stub Database Server Server Client Stub RMI Database Browser Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Object Web Systems: (b) JDBC-based: Java Applets + JDBC gateway programs Client:Browser + Java Applets + JDBC client Server:JDBC driver to a specific DB driver Features:Supporting structured data and interactions. JDBC communications between clients and server Intensive data centered applications with rich GUI support. Applications: Intranet Web-base application systems, tools, group-ware. Pros:Intranet accesses, platform independent. Support multithreading server. Supporting Complex GUI interface and data structure. Less code and effort, better reliability. Cons:No secured communications. Client and server must be written in Java. Internet Database Gateway Database Client (JDBC-Based) Java Applets Database Server JDBC (b) Tier 1 Tier 3Tier 2 Database Browser Direct JDBC Connection Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Object Web Systems: (b) Java-based: Java Applets + JDBC gateway programs Client:Browser + Java Applets + JDBC client Server:JDBC driver to a specific DB driver Features:Supporting simply structured data and interactions. HTTP-based communication between clients and server. Intensive data centered applications with rich GUI support. Applications: Intranet Web-base application systems, tools, group-ware. Pros:Intranet accesses, platform independent. Support multithreading server, scalable to multiple servers. Supporting Complex GUI interface. Cons:No secured communications. Client and server must be written in Java. Limitation on providing scalable servers. Internet Database Gateway Database Client (JDBC-Based) Java Applets Database Server JDBC (c) Tier 1 Tier 3 Tier 2 Database Browser Web Server Java Servlet HTTP Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

- ( ) Object Web Systems: (c) Java and CORBA (such as JOE, Iona): Browser user client Internet Web Server HTML Forms HTML Tables Gateway Programs CGI HTML Forms + Java Applets Database Server Database HTTP (c) Tier 1 Tier 3 Tier 2 CORBA IIOP HTTP CORBA IIOP ORB Application Proxy Server CORBA OrbixWeb - CORBA avoids the CGI bottleneck - CORBA provides a scalable server-to-server infrastructure - CORBA extends Java with a distributed object infrastructure Application 1 Application i CORBA Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Browser user client Internet Web Server HTML Forms HTML Tables Gateway Programs CGI/ISAPI HTML Forms + DocObjects SQL Server HTTP (d) Tier 1 Tier 3 Tier 2 Network OLE HTTP Network OLE COM ORB Server Actives - ( ) Object Web Systems: (d) The Microsoft Object Web Repository/cash of DocObjects or ActiveX Doc. Exchange OLE TP Monitor ActiveXs Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Browser user client Internet Web Server HTML Forms HTML Tables Gateway Programs CGI HTML Forms + JavaAplets Database HTTP (d) Tier 1 Tier 3 Tier 2 HTTP EJB Server JDBC - ( ) Object Web Systems: (d) The EJB-Based Object Web Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999 Application Programs DB Server

Browser user client Internet Web Server HTML Forms HTML Tables Gateway Programs CGI HTML Forms + Java Applets DBMS HTTP (d) Tier 1 Tier 3 Tier 2 CORBA IIOP HTTP CORBA IIOP & Compound Doc. ORB Server Actives - ( ) Object Web Systems: (e) The CORBA/Cyberdog Object Web Bento Doc. Or OODBMS Lotus Notes TP Monitor Compound Doc. Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Java Applet Encapsulation Program MVS System SNA TCP/IP An encapsulation programs puts a more friendly face on a legacy system Legacy System Ordering Encapsulation Program Java Applets Place order user An encapsulation can present an interface different from the legacy system Bridging Legacy Systems to the Web: Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Standalone Java Application Java Server Applet in Web Browser HTTPRMI A Java System Legacy System Java Encapsulation Legacy System Translate a legacy interface into something newer clients can deal with Web Server Legacy System Newer Work Stations RMI/CORBA Bridging Legacy Systems to the Web: Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Legacy System SNA Hardware Java client RMI/CORBA Native methods to access a legacy system Java Applet in Web Browser CORBA Front-End Legacy System CORBA expands the accessibility of an encapsulation system Java Front-End Standalone Java Application C++ Application CORBALegacy protocol Native Methods Bridging Legacy Systems to the Web: Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Java Encapsulation New Workstations RMI/CORBA Legacy terminals and new workstations access the new system Legacy System Java Encapsulation Java client An encapsulation can combine several systems together New Application Newer Database New System Legacy data All data RMI/CORBA New data All data Legacy Terminals Legacy Terminals Terminal Population Bridging Legacy Systems to the Web: Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

Java Web Server Servlet Legacy System Web access to legacy systems involves a servlet Java Web Server Servlet Encapsulation Legacy System Web access to legacy system involves a servlet and an encapsulation (servlet and encapsulation reside in the same machine) Encapsulation Java method calls Legacy Protocol RMI Bridging Legacy Systems to the Web: Topic: An Overview of Architectures for Web-Based Application Systems Jerry Gao Ph.D.5/1999

: HTML-based Thin Client Layer - Hypertext client --> based on HTML pages + hypertext links - Simple interactions between users and systems - Stateless client-server Communications - No cash on the client side - No data verification and validation on the client side Structure:a) Linear Structure,b) Tree Structure,c) Index Structure d) Network Structure,e) Simple Window Menu Structure (a) (b) (c) (d) GUI P1 GUI P2 GUI P4 GUI P2 (e) Jerry Gao Ph.D.5/1999 Topic: An Overview of Architectures for Web-Based Application Systems

: Java Client (Thin - Thick) - HTML forms embedded Java Applets - Cash data on the client side - Stateless/State client-server Communications - Completed data verification and validation on the client side - Support complex GUI structure and graphic display Structure:a) Single Applet b) Multiple Applets in a HTML page (with multiple frames) c) Multiple Applets in different HTML pages Application GUI Applet Communication Security ControlWork Flow Control Client Data LoaderApplet Loader Access ControlClient DB TimerTool BarHelp Application GUI Print JavaIDL Filter/Parser Jerry Gao Ph.D.5/1999 Topic: An Overview of Architectures for Web-Based Application Systems

Now: The Web Client (Three Client Models): a) Browser as Desktop: It assumes that people live within their browsers. This is the current Netscape model of the world. b) Web-Enabled Desktop Components: Every thing on the desktop is Web-enabled; the idea is that you will be able to access the Web from within any application or component without starting a browser. This is the Cyberdog model of the world; Microsoft will also support this model in Windows 97. c) Shippable Places: This lets you access the Web from within your places. A place can have multiple concurrent sessions with Web object servers. In addition, multiple places can be concurrently active on the same desktop. The Object Web may end up supporting all three models. A) Browser as Desktop B) Web-Enabled Desktop Components C) Shippable Places Jerry Gao Ph.D.5/1999 Topic: An Overview of Architectures for Web-Based Application Systems

- Trade-off factors in architecture design of web-based application systems (a) Considering factors: - System performance - Fault tolerance and recovery - System scalability - System complexity - System extendibility - System flexibility - Reusability - Easy to maintain - Portability - Easy to change Jerry Gao Ph.D.5/1999 Topic: An Overview of Architectures for Web-Based Application Systems