A.1.2 Features Introduced in the JDBC 2.0 Optional Package

The following features, which were introduced in the javax.sql package, are now part of the JDBC 3.0 API and are included in the J2SE version 1.4:

• Using a DataSource Object to Get a Connection
Using the JNDI API and the new DataSource interface, an application does not need to specify a driver name in its code to make a connection to a data source. It can specify a logical name that has been registered with a JNDI naming service and retrieve a DataSource object that will get a connection to the desired data source. This capability makes code more portable and much easier to maintain.

• Connection Pooling
Connection pooling allows an application to (re)use database connections that have already been established instead of always having to create new connections. Because creating and destroying database connections is expensive, this feature is important for good performance, especially for server applications.
The JDBC 2.0 Optional Package API provides hooks that allow connection pooling to be implemented on top of the JDBC driver layer. This makes it possible to have a single cache of connections available for all of the JDBC drivers in use.

• Support for Distributed Transactions
The JDBC 2.0 Optional Package API allows a JDBC driver to support the standard two-phase commit protocol defined in the Java Transaction API (JTA). This means that a transaction may be distributed over multiple servers, which lets developers write enterprise applications using Enterprise JavaBeansTM components that are transactional across multiple DBMS servers.

• Rowsets
RowSet objects are simply containers for tabular data that can be implemented on top of the JDBC API. Rowsets make it possible to pass rows of data across a network, so they are likely to be used extensively in distributed applications. Rowsets may be very lean by being disconnected from a data source, making it possible to display data on a thin client. They also make it possible to use scrolling when the underlying DBMS does not support scrollable result sets. A rowset is a JavaBeansTM component and consequently easy to use in building an application, especially with a development tool.
Typically, a third party will provide a RowSet implementation, and the application programmer just uses it. The API for a RowSet implementation is generally very easy to use because most of a rowset's functionality is inherited from the ResultSet interface. The more complicated aspects of a rowset take place internally and are invisible to the application programmer. There are currently three Early Access implementations of the RowSet interface available from the Java Developer Connection (http://developer.java.sun.com/developer).