To store, organize, and retrieve data, most applications use relational databases. J2EE applications access relational databases through the JDBC API. Before an application can access a database, it must get a connection.
At runtime, here’s what happens when an application connects to a database:
Given the resource’s JNDI name, the naming and directory service locates the JDBC resource. Each JDBC resource specifies a connection pool.
Behind the scenes, the application server retrieves a physical connection from the connection pool that corresponds to the database. The pool defines connection attributes such as the database name (URL), user name, and password.
The applications access the database by making calls to the JDBC API. The JDBC driver translates the application’s JDBC calls into the protocol of the database server.
The application server returns the connection to the connection pool. Once it’s back in the pool, the connection is available for the next application.
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