Dynamically load classes that need classpath reference in Java

Question

I'm making a small console program which loads all the class files in a folder as "plugins", so that the program can be customizable by adding new classes.

Here is the problem: a plugin uses the SQL library to provide a simple querying system to a database. In order to include the jdbc driver it has the following code:

String driver = "com.mysql.jdbc.Driver";
Class.forName(driver).newInstance();

I compiled it adding the driver jar to the classpath:

javac -classpath ./libs/mysql-connector-java-5.1.40-bin.jar sqlquery.java

When I run the main jar which loads the plugin's .class file, even though I specify the driver jar in the program classpath, it throws a ClassNotFoundException when calling the com.mysql.jdbc.Driver class.

What can I do?

Answer 1

You should use either -jar or -cp to load the classes into the classpath, you can't combine the two .

Try this:

java -classpath "main.jar;./plugins/libs/mysql-connector-java-5.1.40-bin.jar" sqlquery.java