Today, there are five types of JDBC drivers in use:
Type 5 JDBC drivers (such as DataDirect JDBC drivers) offer advanced functionality and superior performance over other driver types.
Type 4 drivers are the most common and are designed for a particular vendor's database.
In contrast, Type 3 is a single JDBC driver used to access a middleware server, which, in turn, makes the relevant calls to the database. A good example of Type 3 JDBC driver is the DataDirect SequeLink JDBC driver.
Type 1 JDBC drivers are used for testing JDBC applications against an ODBC data source. Type 2 JDBC drivers require a native database API to be used. Both Type 1 and Type 2 JDBC driver types mix a Java-based API with another API.
The following figure shows a side-by-side comparison of the implementation of each of the JDBC driver types. All four implementations show a Java application or applet using the JDBC API to communicate through the JDBC Driver Manager with a specific JDBC driver type.
See the JDBC Overview page on the Oracle web site for details about the four types of JDBC drivers.