Java Reference
In-Depth Information
These are some advantages of a three-tier architecture:
Performance can be improved by separating the application server and database server.
Business logic is clearly separated from the database.
Client applications can use a simple protocol such as CGI to access services.
The three-tier model shown in
Figure 1-3
is common in Web applications. In this
scenario, the client tier is frequently implemented in a browser on a client machine;
the middle tier is implemented in a Web server with a servlet engine; and the
database management system runs on a dedicated database server.
Figure 1-3:
The three-tier model is typical of Web applications.
These are the main components of a three-tier architecture:
Client tier
— Typically, this is a thin presentation layer that may be implemented using a Web
browser.
Middle tier
— This tier handles the business or application logic. This may be implemented
using a servlet engine such as Tomcat or an application server such as JBOSS. The JDBC driver
also resides in this layer.
Data source layer
— This component includes the RDBMS.
Part III
of this topic illustrates additional capabilities of the JDBC API. It provides a
three-tier application that uses a Web browser as the client, an Apache/Tomcat
server as the middle tier, and a relational database management system as the
database tier.
Summary
This chapter has given an overview of how Relational Database Management
Systems work. The key building blocks of relational databases have been introduced,
and will be reviewed in more detail in subsequent chapters. The following key topics
have been discussed:
Creating and normalising databases and their constituent tables.
Using primary and foreign keys to link tables
Using the Structured Query Language
Understanding transactions and transaction management
