Data source drivers, such as Microsoft's Open Database Connectivity (ODBC) drivers, sit between one's programming language and a data source and provide a common way to connect to a data source and query it. Most programmers who use SQL Server to drive Web applications are familiar with the ODBC layer through VBScript or Java; Java uses its own middleware layer, called Java Database Connectivity (JDBC). However, Microsoft's JDBC for SQL Server hasn't been updated in a long time and isn't very well supported. Sun has JDBC middleware, too, but it isn't particularly functional either.
Thankfully, several open-source programmers have stepped in and written their own Java driver for SQL Server: jTDS. jTDS is free, released under the provisions of the GNU Lesser General Public License (LGPL), so it can be tweaked and modified as freely as you wish. Its performance is comparable to (and in some cases better than) many commercially produced middleware libraries for Java.
Installing jTDS is simple enough: Simply place the .JAR file for the driver into the Java application's classpath. jTDS provides full support for all JDBC 3.0 features, including save points and unlimited connections. It does not yet support connection pooling or row sets (partly because there are implementations for these already available elsewhere; see the documentation). It does, however, have experimental support for XA distributed transactions.
Most importantly, jTDS supports many SQL Server specific features like named-pipes connections, which are very important when you're not working across a network, ASCII/Unicode, SSL encryption, Windows authentication, SQL Server named instances and quite a few others. This makes it especially appealing to SQL Server developers who are using Java as their programmatic front-end, who want to customize heavily and who are running into the performance and developmental limitations of the existing JDBCs.
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Serdar Yegulalp is editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!