|
J2EE Compliance: Java Transaction API and javax.sql Interfaces
J2EE, or the Java 2 Platform, Enterprise Edition, is a standard
for development of enterprise applications based on reusable components in
a multi-tier environment. In addition to the features of the Java 2 Platform,
Standard Edition (J2SE) J2EE adds support for Enterprise Java Beans (EJBs),
Java Server Pages (JSPs), Servlets, XML and many more. The J2EE architecture
is used to bring together existing technologies and enterprise applications
in a single, manageable environment.
Derby is a
J2EE-conformant component in a distributed J2EE system. As such, Derby is
one part of a larger system that includes, among other things, a JNDI server,
a connection pool module, a transaction manager, a resource manager, and user
applications. Within this system, Derby can
serve as the resource manager.
For more information on J2EE, see the
J2EE specification available at http://java.sun.com/javaee/reference/ .
In
order to qualify as a resource manager in a J2EE system, J2EE requires these
basic areas of support:
- JNDI support
Allows calling applications to register names for databases
and access them through those names instead of through database connection
URLs. Implementation of one of the JDBC interfaces, javax.sql.DataSource, provides
this support.
- Connection pooling
A mechanism by which a connection pool server keeps
a set of open connections to a resource manager (Derby).
A user requesting a connection can get one of the available connections from
the pool. Such a connection pool is useful in client/server environments because
establishing a connection is relatively expensive. In an embedded environment,
connections are much cheaper, making the performance advantage of a connection
pool negligible. Implementation of two of the JDBC interfaces, javax.sql.ConnectionPoolDataSource
and javax.sql.PooledConnection, provide this support.
- XA support
XA is one of several standards for distributed transaction
management. It is based on two-phase commit. The javax.sql.XAxxx interfaces,
along with java.transaction.xa package, are an abstract implementation
of XA. For more information about XA, see X/Open CAE Specification-Distributed
Transaction Processing: The XA Specification, X/Open Document No. XO/CAE/91/300
or ISBN 1 872630 24 3. Implementation of the JTA API, the interfaces of the
java.transaction.xa package (javax.sql.XAConnection, javax.sql.XADataSource, javax.transaction.xa.XAResource, javax.transaction.xa.Xid, and javax.transaction.xa.XAException),
provides this support.
With the exception of the core JDBC interfaces, these interfaces
are not visible to the end-user application; instead, they are used only by
the other back-end components in the system. Note: For information on the
classes that implement these interfaces and how to use Derby as
a resource manager, see Chapter 6, "Using Derby as
a J2EE Resource Manager" in the Derby Developer's Guide.
|
