为什么hibernate数据库模式导出的ant任务失败？

Question

我的Ant数据库架构导出任务是：

<!--export a DB schema-->
<taskdef name="hibernatetool"
        classname="org.hibernate.tool.ant.HibernateToolTask"
        classpathref="project.classpath"/>

<target name="schemaexport"
        depends="compile, copymetafiles"
        description="Exports a generated schema to DB and file">
        <hibernatetool destdir="${basedir}">
            <classpath path="${build.dir}"/>
            <configuration
                configurationfile="${build.dir}/hibernate.cfg.xml"/>
                <hbm2ddl
                drop="true"
                create="true"
                export="true"
                outputfilename="hellohibernate-ddl.sql"
                delimiter=";"
                format="true"/>
        </hibernatetool>
</target>

来自控制台的错误消息是：

schemaexport:
[hibernatetool] Executing Hibernate Tool with a Standard Configuration
[hibernatetool] 1. task: hbm2ddl (Generates database schema)
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.annotations.common.Version <clinit>
[hibernatetool] INFO: Hibernate Commons Annotations 3.2.0.Final
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Environment <clinit>
[hibernatetool] INFO: Hibernate 3.6.0.Final
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Environment <clinit>
[hibernatetool] INFO: hibernate.properties not found
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Environment buildBytecodeProvider
[hibernatetool] INFO: Bytecode provider name : javassist
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Environment <clinit>
[hibernatetool] INFO: using JDK 1.4 java.sql.Timestamp handling
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Configuration configure
[hibernatetool] INFO: configuring from file: hibernate.cfg.xml
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.util.DTDEntityResolver resolveEntity
[hibernatetool] WARNING: recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Configuration addResource
[hibernatetool] INFO: Reading mappings from resource : Hello/Message.hbm.xml
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.util.DTDEntityResolver resolveEntity
[hibernatetool] WARNING: recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!
[hibernatetool] Nov 22, 2010 11:55:17 AM org.hibernate.cfg.Configuration doConfigure
[hibernatetool] INFO: Configured SessionFactory: null

有什么问题？是什么原因??