Don't connect tomcat with mysql

Hi? I need jira enterprise's database on mysql. However we have tried to convert hsql to mysql using help file , tomcat doesn't connect to mysql when start up it.it waiting for me or error page show me.

driverName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost/jiradb?autoReconnect=true"
connectionName="jirauser" connectionPassword="xxxxxxx"

Now, I've also tried the standard mysql driver name
(com.mysql.jdbc.Driver), with the same affects.
I'm using mysql-connector-java-3.0.16-ga-bin.jar
a copy in /common/lib/ and .../myApp/WEB-INF/lib/

What should I do now? Please advise me.