Loading Derby JDBC Driver Classes

JDBC Tutorials - Herong's Tutorial Examples

∟Loading Derby JDBC Driver Classes

This section describes how to load the Derby JDBC driver classes.

Derby JDBC driver has two driver classes for Derby (Java DB) running in two different modes:

1. Embedded Driver Class, org.apache.derby.jdbc.EmbeddedDriver - Used to create connections to Derby (Java DB) running in embedded mode. The JAR file and the connection URL format for the embedded driver class are listed below:

Class Name: org.apache.derby.jdbc.EmbeddedDriver
JAR File (Windows): %DERBY_HOME%\lib\derby.jar
JAR File (Linux and macOS): $DERBY_HOME/lib/derby.jar
Connection URL: jdbc:derby:<database>

2. Client Driver Class, org.apache.derby.client.ClientAutoloadedDriver - Used to create connections to Derby (Java DB) running in Network Server mode. The JAR file and the connection URL format for the client driver class are listed below:

Class Name: org.apache.derby.client.ClientAutoloadedDriver
JAR File (Windows): %DERBY_HOME%\lib\derbyclient.jar
JAR File (Linux and macOS): $DERBY_HOME/lib/derbyclient.jar

Since I am running Derby server in network mode, I need to include the JDBC driver JAR file, derbyclient.jar, in the -classpath (or -cp) option when compiling and running my Java programs. For example:

(on Windows)
herong> javac -cp %DERBY_HOME%\lib\derbyclient.jar SomeClass.java
herong> java -cp .;%DERBY_HOME%\lib\derbyclient.jar SomeClass

(on Linux or macOS)
herong> javac -cp $DERBY_HOME/lib/derbyclient.jar SomeClass.java
herong> java -cp $DERBY_HOME/lib/derbyclient.jar SomeClass

After identified the Derby JDBC driver JAR file, I need to find a way to load it in my Java applications. There are 5 options to do this:

1. Do nothing. The DriverManager class will automatically load all driver classes that in JAR fiels in the classpath.
2. Call the forName() method like this: Class.forName("org.apache.derby.client.ClientAutoloadedDriver"). This is the commonly used way of load a driver class.
3. Create a dummy driver object like this: "new org.apache.derby.client.ClientAutoloadedDriver()". This forces you to include the required JAR file at compilation time.
4. Retrieve the static class object from the driver class like this: "Class c = org.apache.derby.client.ClientAutoloadedDriver.class ". This also forces you to include the required JAR file at compilation time.
5. Set the system property jdbc.drivers in the configuration file or in the command line option "-D". For example: "java -Djdbc.drivers=org.apache.derby.client.ClientAutoloadedDriver application".

Of course, I like to try the "Do nothing" option. Here is my testing Java program:

/* AutoLoadJdbcDriver.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.sql.*;
import java.util.*;
public class AutoLoadJdbcDriver {
  public static void main(String [] args) {
    Connection con = null;
    try {
      listDrivers();

// Find the driver for a given URL
      Driver driverClass = (Driver) DriverManager.getDriver(
        "jdbc:derby://somehost/somedb");
      System.out.println("\nDriver for jdbc:derby://somehost/somedb");
      System.out.println("   "+driverClass.getClass().getName());

      listDrivers();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
    }
  }
  private static void listDrivers() {
    Enumeration driverList = DriverManager.getDrivers();
    System.out.println("\nList of drivers:");
    while (driverList.hasMoreElements()) {
      Driver driverClass = (Driver) driverList.nextElement();
      System.out.println("   "+driverClass.getClass().getName());
    }
  }
}

The output below confirms that the DriverManager class is able to load any JDBC driver classes as long as their JAR files are included in the classpath.

...
(on Windows)
herong> javac -cp %DERBY_HOME%\lib\derbyclient.jar AutoLoadJdbcDriver.java
herong> java -cp .;%DERBY_HOME%\lib\derbyclient.jar AutoLoadJdbcDriver

(on Linux or macOS)
herong> javac -cp $DERBY_HOME/lib/derbyclient.jar AutoLoadJdbcDriver.java
herong> java -cp .:$DERBY_HOME/lib/derbyclient.jar AutoLoadJdbcDriver

List of drivers:
   org.apache.derby.client.ClientAutoloadedDriver

Driver for jdbc:derby://somehost/somedb
   org.apache.derby.client.ClientAutoloadedDriver

List of drivers:
   org.apache.derby.client.ClientAutoloadedDriver

Note that the Derby JDBC driver class name has been changed. In older Derby versions, it was called as, org.apache.derby.jdbc.ClientDriver. Here is the output of the same program running with Derby 10.11:

List of drivers:
   org.apache.derby.jdbc.ClientDriver

Driver for jdbc:derby://somehost/somedb
   org.apache.derby.jdbc.ClientDriver

List of drivers:
   org.apache.derby.jdbc.ClientDriver