I am trying to generate DDL from an XML hibernate mapping file, I do this using the hbm2ddl ant task. This worked well until I added my own custom UserType to the mapping. Now when I run hbm2ddl I get the following expection:

java.lang.NoClassDefFoundError: org/hibernate/usertype/UserType

I have hibernate3.jar on the classpath for the <taskdef> which defines hibernatetool and I have also tried putting the following inside the <hibernatetool> element:

<classpath>
<pathelement location="lib/hibernate3.jar"/>
<fileset dir="lib" includes="*.jar"/>
</classpath>

All to no avail. Why can't hibernatetool see the contents of my hibernate3.jar?

I am using hibernate-tools 3.2.0GA.

Here is a fragment of the stacktrace with ant on verbose mode:

--- Nested Exception ---
java.lang.NoClassDefFoundError: org/hibernate/usertype/UserType
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at org.apache.tools.ant.AntClassLoader.findBaseClass(AntClassLoader.java:1414)
at org.apache.tools.ant.AntClassLoader.loadClass(AntClassLoader.java:1068)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at org.hibernate.util.ReflectHelper.classForName(ReflectHelper.java:100)
at org.hibernate.type.TypeFactory.heuristicType(TypeFactory.java:223)
at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:260)
at org.hibernate.mapping.Column.getSqlTypeCode(Column.java:138)
at org.hibernate.mapping.Column.getSqlType(Column.java:182)
at org.hibernate.mapping.Table.sqlCreateString(Table.java:394)
at org.hibernate.cfg.Configuration.generateSchemaCreationScript(Configuration.java:848)
at org.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:94)
at org.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:61)
at org.hibernate.tool.ant.Hbm2DDLExporterTask.execute(Hbm2DDLExporterTask.java:45)

the error you are showing is because of you mixing hibernate jars - some on the task classpath and others on the <hibernatetool>

The only thing that should be on the hibernatetool classpath is your pojo/usertype classes, not any hibernate or other related jars.

That was indeed the problem. OK, it's clear now, I put the hibernate jars on the taskdef classpath and my classes on the hibernatetool classpath and it all works fine. Thanks!