Tomcat does not recognize the MySQL .jar library

Question

I tried several different ways such that Tomcat loads the MySQL drivers when running my web application. I'm using Ubuntu 8.04, and the libraries come from the libmysql-java package. They are located in the directory shown below:

~$ ls /usr/share/java/mysql*
/usr/share/java/mysql-connector-java-5.1.5.jar

My CLASSPATH includes this file:

~$ echo $CLASSPATH
.:/usr/lib/jvm/java-6-sun/bin:/usr/local/tomcat/lib/servlet-api.jar:/usr/share/java/mysql-connector-java-5.1.5.jar

I even put a copy of the .jar file in my WEB-INF/lib/ directory in my web app:

/usr/local/tomcat/webapps/ohms/WEB-INF/lib$ ls
mysql-connector-java-5.1.5.jar

After making these changes, I restart Tomcat, re-compile my classes, restart Tomcat again. Also, I am importing the necessary libraries using import java.sql.*;

However I am still getting the java.lang.ClassNotFoundException: com.mysql.jdbc.Driver error when it runs the line Class.forName("com.mysql.jdbc.Driver").newInstance();

What am I doing wrong here?

Answer 1

Put it in TOMCAT_HOME/lib. (I seem to recall that on older versions of Tomcat, it's TOMCAT_HOME/server/lib?)

It's not going to work in WEB-INF/lib since the container needs access to the library, and, that is putting it in the classloader of one web app, not the container. While I would have imagined the CLASSPATH approach would work, it's not the standard way to do this. Perhaps there is some other snag that's preventing it from working.

Answer 2

I guess we should also ask, why are you trying to instantiate this class? I don't even know that this exists in MySQL Connector/J anymore as it is the very old way to use a database with JDBC.

The only class I can imagine you want to instantiate is their DataSource implementation, MysqlDataSource. But even that's unlikely. Usually you configure the DataSource in conf/server.xml, then look it up with JNDI. That way your app itself has no dependency on MySQL.

Answer 3

Tomcat ignores any CLASSPATH environment variable, as do all Java EE app servers and IDEs. That does you no good at all. I don't set one on any machine that I use.

The JAR needs to go in Tomcat server/lib for Tomcat 5.x and /lib for 6.x.

You don't need to call newInstance(); Class.forName("com.mysql.jdbc.Driver") is sufficient to register the driver class.