Hi All,
I am getting an Communications link failure error when connecting to my database, so I changed my hibernate XML file to have autoReconnect=true. Which did not solve the problem.
Then I tried the c3po approach and the problem still persists.
I tried the approach of setting wait time, using select 1 query to test the connection etc.. but did not work.

Now I decided to configure the db using data source. This time I can't make a connection. Hibernate is not reading the data source. While creating the connection I am getting an exception that states driver class is ' ' and url = null. I already gave this configuration in the context.xml file under META_INF folder.
I am using Tomcat 6 and mysql as my db.

Any help will be greatly appreciated.

Here are my configuration files....
hibernate.cfg.xml XML is
----------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory >
<property name="connection.datasource">java:comp/env/jdbc/mydb</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="current_session_context_class">thread</property>

<mapping resource="path/mytable.hbm.xml"/>
</session-factory>
</hibernate-configuration>


Context XML under META-INF/context.xml of the project is
----------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<Context antiJARLocking="true" path="/Myproject">
<resource name="jdbc/mydb"
global="jdbc/mydb"
auth="Container"
type="javax.sql.DataSource"
username="username"
password="password"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/dbname?autoReconnect=true"
maxActive="8"
maxIdle="4"/>
</Context>
(Note: I tried putting the resource contents in tomcat's $CATALINA_HOME/conf/context.xml as well. )



web.xml
----------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
...
<resource-ref>
<description>My DB Connection</description>
<res-ref-name>jdbc/mydb</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
</web-app>

HibernateUtil.java .......................
public class HibernateUtil {
private static final SessionFactory sessionFactory;
static {
try {
// Create the SessionFactory from standard (hibernate.cfg.xml)
sessionFactory = new Configuration().configure().buildSessionFactory();

} catch (Throwable ex) {
throw new ExceptionInInitializerError(ex);
}
}

public static SessionFactory getSessionFactory() {

return sessionFactory;

}
}


I am getting this exception when I do sessionFactory.getSession().

----------------------------------------------------
The exception I am getting is

[2010-07-21 11:11:41,991][org.hibernate.impl.SessionFactoryObjectFactory][DEBUG]::::initializing class SessionFactoryObjectFactory
[2010-07-21 11:11:41,993][org.hibernate.impl.SessionFactoryObjectFactory][DEBUG]::::registered: ff80818129f58f620129f58f63a60000 (unnamed)
[2010-07-21 11:11:41,993][org.hibernate.impl.SessionFactoryObjectFactory][INFO ]::::Not binding factory to JNDI, no JNDI name configured
[2010-07-21 11:11:41,993][org.hibernate.impl.SessionFactoryImpl][DEBUG]::::instantiated session factory
[2010-07-21 11:11:41,996][org.hibernate.impl.SessionFactoryImpl][DEBUG]::::Checking 0 named HQL queries
[2010-07-21 11:11:41,997][org.hibernate.impl.SessionFactoryImpl][DEBUG]::::Checking 0 named SQL queries
[2010-07-21 11:11:42,029][org.hibernate.impl.SessionImpl][DEBUG]::::opened session at timestamp: 12797251020
[2010-07-21 11:11:42,083][org.hibernate.transaction.JDBCTransaction][DEBUG]::::begin
[2010-07-21 11:11:42,084][org.hibernate.jdbc.ConnectionManager][DEBUG]::::opening JDBC connection
[2010-07-21 11:11:42,087][org.hibernate.util.JDBCExceptionReporter][DEBUG]::::Cannot open connection [???]
org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1150)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880)
at org.hibernate.connection.DatasourceConnectionProvider.getConnection(DatasourceConnectionProvider.java:69)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:423)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:119)
at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:57)
at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1326)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
at $Proxy0.beginTransaction(Unknown Source)