有关hibernate的事物

报错如下：
严重: Servlet.service() for servlet action threw exception
org.hibernate.TransactionException: Transaction not successfully started
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:100)
at com.jadecenter.filter.HibernateFilter.doFilter(HibernateFilter.java:34)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.jadecenter.filter.ChangeCharsetFilter.doFilter(ChangeCharsetFilter.java:28)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
感觉是由于我在好几个dao中的save方法中加入了：
public void save(Project transientInstance) {
log.debug("saving Project instance");
Transaction tran = getSession().beginTransaction(); try {
getSession().save(transientInstance);
getSession().flush();
tran.commit();
getSession().close();
log.debug("save successful");
} catch (RuntimeException re) {
log.error("save failed", re);
throw re;
}
}
导致事物嵌套了，请大侠该如何解决这个问题，不嵌套的话，有的就保存不到数据库了！