我在JBoss服务器上使用Hibernate。我得到下面的错误。

当我尝试在同一会话中第二次连接到数据库时，发生错误。

另外，我还会收到错误消息“为您关闭连接。请关闭您的连接”。

    14:28:37,869 ERROR [HibernateUtil] HibernateException  occurred in executeQuery  method   in  HibernateUtil class 
    org.hibernate.exception.GenericJDBCException: could not execute query
    at   org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:126)
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:114)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.loader.Loader.doList(Loader.java:2231)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2125)
    at org.hibernate.loader.Loader.list(Loader.java:2120)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401)
    at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:361)
    at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196)
    at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1148)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102)
    at com.a.amc.dao.utils.HibernateUtil.executeQuery(HibernateUtil.java:154)
    at com.a.amc.service.impl.CityServiceImpl.isCityExists(CityServiceImpl.java:142)
    at com.a.amc.service.impl.CityServiceImpl.addCity(CityServiceImpl.java:38)
    at com.a.amc.web.actions.CityAction.addCity(CityAction.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)

14:28:37,869 ERROR [JDBCTransaction] Could not toggle autocommit
java.sql.SQLException: Connection is not associated with a managed connection.org.jboss.resource.adapter.jdbc.jdk6.WrappedConnectionJDK6@1269ca1
    at org.jboss.resource.adapter.jdbc.WrappedConnection.lock(WrappedConnection.java:81)
    at org.jboss.resource.adapter.jdbc.WrappedConnection.setAutoCommit(WrappedConnection.java:454)
    at org.hibernate.transaction.JDBCTransaction.toggleAutoCommit(JDBCTransaction.java:228)
    at org.hibernate.transaction.JDBCTransaction.rollbackAndResetAutoCommit(JDBCTransaction.java:220)
    at org.hibernate.transaction.JDBCTransaction.rollback(JDBCTransaction.java:196)
    at com.a.amc.dao.utils.HibernateUtil.executeQuery(HibernateUtil.java:159)
    at com.a.amc.service.impl.CityServiceImpl.isCityExists(CityServiceImpl.java:142)
    at com.a.amc.service.impl.CityServiceImpl.addCity(CityServiceImpl.java:38)
    at com.a.amc.web.actions.CityAction.addCity(CityAction.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)

14:28:37,869 ERROR [JDBCTransaction] JDBC rollback failed
java.sql.SQLException: Connection is not associated with a managed connection.org.jboss.resource.adapter.jdbc.jdk6.WrappedConnectionJDK6@1269ca1
    at org.jboss.resource.adapter.jdbc.WrappedConnection.lock(WrappedConnection.java:81)
    at org.jboss.resource.adapter.jdbc.WrappedConnection.rollback(WrappedConnection.java:496)
    at org.hibernate.transaction.JDBCTransaction.rollbackAndResetAutoCommit(JDBCTransaction.java:217)
    at org.hibernate.transaction.JDBCTransaction.rollback(JDBCTransaction.java:196)
    at com.a.amc.dao.utils.HibernateUtil.executeQuery(HibernateUtil.java:159)
    at com.a.amc.service.impl.CityServiceImpl.isCityExists(CityServiceImpl.java:142)
    at com.a.amc.service.impl.CityServiceImpl.addCity(CityServiceImpl.java:38)
    at com.a.amc.web.actions.CityAction.addCity(CityAction.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)

14:28:37,869 ERROR [CityServiceImpl] Exception  occurred in isCityExists method in  CityServiceImpl
org.hibernate.TransactionException: JDBC rollback failed
    at org.hibernate.transaction.JDBCTransaction.rollback(JDBCTransaction.java:204)
    at com.a.amc.dao.utils.HibernateUtil.executeQuery(HibernateUtil.java:159)
    at com.a.amc.service.impl.CityServiceImpl.isCityExists(CityServiceImpl.java:142)
    at com.a.amc.service.impl.CityServiceImpl.addCity(CityServiceImpl.java:38)
    at com.a.amc.web.actions.CityAction.addCity(CityAction.java:50)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)

可能是什么原因，如何解决这种情况？