DAT602 Database Application Development Lecture 12 C/S Model Database Application

In this lecture, you will see how to create a simple Client / Server model database application. We will build a simple library book management system for demonstration. Database Application Development - Lecture 12

There are basically two major kinds of modern architectures: two-tier client/server and three- tier—also commonly called n-tier. Database Application Development - Lecture 12

Two-tier client/server A two-tier application ideally provides multiple workstations with a uniform presentation layer that communicates with a centralized data storage layer. The presentation layer is generally the client, and the data storage layer is the server. Database Application Development - Lecture 12

Two-tier client/server Following diagram shows how two-tier systems give clients access to centralized data. Database Application Development - Lecture 12

Two-tier limitations - Fat clients Two-tier, fat-client systems are notorious for their inability to adapt to changing environments and scale with growing user and data volume. Even though a client's primary task is the presentation of data, a fat client is loaded with knowledge completely unrelated to that task. Database Application Development - Lecture 12

Two-tier limitations -Object reuse In one common sense, object reuse is simply code reuse. In two-tier model, code is too close to database server, it is not easy to be modified when business logic changes. Two-tier model lacks flexibility. Database Application Development - Lecture 12

When to use a two-tier design? If you can answer "yes" to each of the questions in the checklist, then a two-tier architecture is likely your best solution. - Does your application emphasize time-to-market over architecture? - Does your application use a single database? - Is your database engine located on a single host? - Is your database likely to stay approximately the same size over time? - Is your user base likely to stay approximately the same size over time? - Are your requirements fixed with little or no possibility of change? - Do you expect minimal maintenance after you deliver the application? Database Application Development - Lecture 12

Three-tier’s advantage - Isolated database connectivity Three-tier model helps you to split presentation layer and data storage layer. Changes of these two layers won’t affect each other. Database Application Development - Lecture 12

Three-tier’s advantage -Centralized business processing These centralized rules for processing data inside business objects are called business rules. No matter what your problem domain is, the rules for how data should be processed rarely change. Database Application Development - Lecture 12

Three-tier’s advantage -Business object presentation The presentation layer of a three-tier application should therefore contain only user interface code that can be modified easily on a whim. The presentation layer of a bank application: The teller window's console at the bank The ATM machine The web applet Database Application Development - Lecture 12

Drawbacks to the three-tier architecture Chief among its drawbacks is the level of complexity it adds to a system. It is also harder to find software engineers who are competent in three-tier programming skills such as transaction management and security. Database Application Development - Lecture 12

In next, I’ll give you a demonstration for how to create a simple two-tie client server database application. This C/S database application is developed for library management. Database Application Development - Lecture 12

Step 1: write your specification of this library application. What kind of users be involved in this application? What features this application should has? Simple hierarchy of your application. Database Application Development - Lecture 12

Extremely Simple Specification In this application, there are two kinds of users: librarian and normal user. Librarians has fully authorization, they can add, modify or remove books, users information, and also can add or modify loan log. Normal users can observe their loan log and check their accounts’ status. This application should consists with two client GUIs, one for librarians, and another for normal users. Database Application Development - Lecture 12

Step: 2 Design and build database of this library application. Diagram: Structure of library application

Step 3: implement basic operation: insert record, remove record, query for each table. Step 4: Design GUI Database Application Development - Lecture 12