3 Overview of New Features
This chapter contains an overview of the new features that are being added to the JDBC
2.0 API.
3.1 Result set enhancements
The JDBC 1.0 API provided result sets that had the ability to scroll in a forward direction
only. Scrollable result sets allow for more flexibility in the processing of results by
providing both forward and backward movement through their contents. In addition,
scrollable result sets allow for relative and absolute positioning. For example, it's possible
to move to the fourth row in a scrollable result set directly, or to move directly to
the third row following the current row, provided the row exists.
The JDBC 2.0 API allows result sets to be directly updatable, as well.
3.2 Batch updates
The batch update feature allows an application to submit multiple update statements
(insert/update/delete) in a single request to the database. This can provide a dramatic
increase in performance when a large number of update statements need to be executed.
3.3 Advanced data types
Increased support for storing persistent Java objects and a mapping for SQL3 data types
such as binary large objects, and structured types, has been added to the JDBC 2.0 API.
An application may also customize the mapping of SQL3 structured types into Java language
classes.
3.4 Rowsets
As its name implies, a rowset encapsulates a set of rows. A rowset may or may not
maintain an open database connection. When a rowset is `disconnected' from its data
source, updates performed on the rowset are propagated to the underlying database using
an optimistic concurrency control algorithm.
Rowsets add support to the JDBC API for the JavaBeans component model. A rowset
object is a Java Bean. A rowset implementation may be serializable. Rowsets can be
created at design time and used in conjunction with other JavaBeans components in a
visual JavaBeans builder tool to construct an application.
3.5 JNDI for naming databases
The Java Naming and Directory Interface (JNDI) can be used in addition to the JDBC
driver manager to obtain a connection to a database. When an application uses JNDI, it
specifies a logical name that identifies a particular database instance and JDBC driver
for accessing that database. This has the advantage of making the application code independent
of a particular JDBC driver and JDBC URL.
3.6 Connection Pooling
The JDBC 2.0 API contains `hooks' that allow connection pooling to be implemented
on top of the JDBC driver layer. This allows for a single connection cache that spans
the different JDBC drivers that may be in use. Since creating and destroying database
connections is expensive, connection pooling is important for achieving good performance,
especially for server applications.
3.7 Distributed transaction support
Support for distributed transactions has been added as an extension to the JDBC 2.0
API. This feature allows a JDBC driver to support the standard 2-phase commit protocol
used by the Java Transaction Service (JTS).
3.8 Other new features
Support for character streams has been added. This means that character data can be retrieved
and sent to the database as a stream of internationalized Unicode characters.
Methods to allow java.math.BigDecimal values to be returned with full precision
have also been added. Support for time zones has been added.
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