Hibernate version:
2.1.6

Mapping documents: -

Code between sessionFactory.openSession() and session.close():

Full stack trace of any exception that occurs:
$ ant eg Buildfile: build.xml
[taskdef] Could not load definitions from resource clovertasks. It could not be found.

eg:
[echo] Remember to place your JDBC driver in the lib directory!
[echo] This target is not runable from a CVS export/checkout!
[java] Exception in thread "main" java.lang.ExceptionInInitializerError
[java] at org.hibernate.auction.Main.main(Main.java:356)
[java] Caused by: org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1f33675 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category) (Caused by org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1f33675 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category))
[java] at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
[java] at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
[java] at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
[java] at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
[java] at net.sf.hibernate.cfg.Configuration.<clinit>(Configuration.java:94)
[java] ... 1 more
[java] Caused by: org.apache.commons.logging.LogConfigurationException: No suitable Log constructor [Ljava.lang.Class;@1f33675 for org.apache.commons.logging.impl.Log4JLogger (Caused by java.lang.NoClassDefFoundError: org/apache/log4j/Category)
[java] at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:413)
[java] at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
[java] ... 5 more
[java] Caused by: java.lang.NoClassDefFoundError: org/apache/log4j/Category
[java] at java.lang.Class.getDeclaredConstructors0(Native Method)
[java] at java.lang.Class.privateGetDeclaredConstructors(Class.java:1610)
[java] at java.lang.Class.getConstructor0(Class.java:1922)
[java] at java.lang.Class.getConstructor(Class.java:1019)
[java] at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:410)
[java] ... 6 more

Name and version of the database you are using:
MySQL 4 - mysql-connector 3.0.14

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt: