Java Servlet Programming, 2nd Edition

Chapter 9. Database Connectivity

It’s hard to find a professional web site today that doesn’t have some sort of database connectivity. Webmasters have hooked online frontends to all manner of legacy systems, including package tracking and directory databases, as well as many newer systems like online messaging, storefronts, and search engines. But web-database interaction comes with a price: database-backed web sites can be difficult to develop and can often exact heavy performance penalties. Still, for many web sites, database connectivity is just too useful to let go. More and more, databases are driving the Web.

This chapter introduces relational databases, the Structured Query Language (SQL) used to manipulate those databases, and the Java Database Connectivity (JDBC) API itself. Servlets, with their enduring lifecycle, and JDBC, a well-defined database-independent database connectivity API, are an elegant and efficient solution for webmasters who need to hook their web sites to backend databases. In fact, both of your authors started working with servlets specifically because of this efficiency and elegance. Although elsewhere in the book we have assumed that you are familiar with Java, this chapter breaks that assumption and begins with a quick course in JDBC.

The biggest advantage for servlets with regard to database connectivity is that the servlet lifecycle (explained in depth in Chapter 3) allows servlets to maintain pools of open database connections. An existing connection ...