一个关于Hibernate奇怪的问题

请问各位一个小问题，我的hibernate全部配置好了，为什么会出现这样的异常呢？我检查过是Transaction tx= session.beginTransaction();这个语句出错，如果我将这条语句去掉，则数据无法写到数据库，请各们帮忙解决一下，急
java.lang.UnsupportedOperationException
        at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSo
urce.java:161)
        at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource
.java:532)
        at net.sf.hibernate.connection.DatasourceConnectionProvider.getConnectio
n(DatasourceConnectionProvider.java:56)
        at net.sf.hibernate.impl.BatcherImpl.openConnection(BatcherImpl.java:278
)
        at net.sf.hibernate.impl.SessionImpl.connect(SessionImpl.java:3264)
        at net.sf.hibernate.impl.SessionImpl.connection(SessionImpl.java:3244)
        at net.sf.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.ja
va:40)
        at net.sf.hibernate.transaction.JDBCTransactionFactory.beginTransaction(
JDBCTransactionFactory.java:19)
        at net.sf.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:2
195)
        at TestHibernate.doGet(TestHibernate.java:11)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:743)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:284)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:204)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:257)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:151)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:567)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(Standard
ContextValve.java:245)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:199)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:151)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:567)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:184)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:151)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:164)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:149)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:567)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:156)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:151)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:567)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:972)        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:20
6)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:833)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ssConnection(Http11Protocol.java:732)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java
:619)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP
ool.java:688)
        at java.lang.Thread.run(Thread.java:566)