Introduction
If
you are a Java web developer who has never written database-related
code, I have some advice for you: don't hold your
breath until you receive this type of assignment!
These recipes show you how to access a database resource by using a
Java Naming and Directory Interface
(JNDI) lookup, which is the most efficient (and probably the most
common) method of accessing database resources in a portable manner.
JNDI is a Java API that is designed to store objects in a
hierarchical tree structure, similar to a filesystem composed of
directories, subdirectories, and files. Servlets and JSPs can then
use the methods of the JNDI API (shown by several examples in this
chapter) to obtain references from Java objects, such as JavaBeans,
and use them in their programs.
For
database code, this usually means
javax.sql.DataSource objects, which are factories
for database connections. The DataSources provide
"connection pools," another very
important web database tool. Connection pools are groups of database
connections shared by servlets, JSPs, and other classes. Application
servers such as WebLogic usually allow you to determine how many
connections are stored in the pool, which database table can be used
by the server to automatically test a connection to determine if it
is fit to be returned to the shared pool, and other pool properties.
These recipes explain the basics of setting up a connection pool on
both Tomcat and WebLogic.
The recipes also cover some other practical database topics, such as
how to call stored procedures in servlets and JSPs, as well as how to
include more than one Structured Query Language (SQL) statement in a
transaction.
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