An Introduction to Network Programming with Java by Jan Graba

Author:Jan Graba
Language: eng
Format: epub, pdf
Publisher: Springer London, London

7.2 SQL and Versions of JDBC

The standard means of accessing a relational database is to use SQL (Structured Query Language). [Readers unfamiliar with SQL are advised to read the appendix on this subject before proceeding further with this chapter.] This is reflected in the fact that the package comprising the core JDBC API is called java.sql.

The original JDBC that was released with JDK 1.1 was JDBC 1.0, which comprised package java.sql. Using this API, it is possible to access data not only from relational databases, but also from spreadsheets and flat files—i.e., from just about any data source. With JDBC 2.0, which appeared in J2SE 1.4, extra functionality was introduced with the additional package javax.sql. Probably the most notable feature of this version was the introduction of the DataSource interface, which now provides the preferred method of making a connection to a database, This is due to the fact that a DataSource object has properties that can be modified. Thus, for example, if the data source is moved to a different server, the property for the server can be changed without requiring the code accessing the data source to be changed. In spite of the fact that the use of a DataSource object is the official preferred method of making connection to a database, the old method of making a connection, which involves the use of the DriverManager class, is still quite commonly used. Both of these techniques will be covered in this chapter.

The latest version of the JDBC API (at the time of writing) is JDBC 4.1, which is included with Java SE 7, and most drivers nowadays adhere to the JDBC 4 standard, which has been included in the Java installation since Java SE 6 (launched in December of 2006). However, users of earlier versions can expect their code to continue to work under Java SE 7, since one of the guiding design principles of each new version has been that of maintaining compatibility with existing applications and drivers.

In the examples that follow in the next two sections, a simple MS Access database will be used for purposes of illustration, which means that the inbuilt JDBC-ODBC bridge driver can be employed (even though, as noted at the end of 7.1, this may not be the best strategy in many commercial applications). Convenient though this may be, in view of the widespread use and availability of MS Access and the inclusion of the JDBC-ODBC bridge driver in the Java installation, it does introduce a couple of complications: (i) we have to create an ODBC Data Source and (ii) we need to use the 32-bit version of Java, even though there is now a 64-bit version. The reason for the latter is that, although a 64-bit version of MS Access does now exist, even Microsoft is recommending that the 32-bit version be installed for the time being: “For these reasons, we recommend running 32-bit Office 2010 even on 64-bit Windows operating systems for better compatibility…When the 64-bit ecosystem for Office is more mature, you’ll be able to easily migrate to 64-bit Office” [http:​/​/​blogs.

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