Exception in beginTransaction

I am using hibernate in my web application,when I am getting exception while:

Transaction tx=session.beginTransaction();

It gives exception once in a while, I am reloading SessionFactory while catching the exception and then it runs fine.

It is working when I am reloading the SessionFactory again.

This is my code snippet:

 session = HibernateFactory.openSession(0);//Passing 0 uses the existing sessionFactory
        if(session.isConnected() && session.isOpen() && session!=null)
        {
           try{
            tx = session.beginTransaction();
            logger.info("Transaction is begin successfully--Transaction is--"+tx);
            }catch(Exception e){
            logger.info("Could not start the transaction--Transaction is--"+tx);
               session = HibernateFactory.openSession(1);//passing 1 is creating new     //--SessionFactory
               tx = session.beginTransaction();//now this runs fine
               logger.info("Inside catch--Obtained session--"+session+"and transaction--"+tx);
               e.printStackTrace();
               logger.error("e.getCause(): "+e.getCause());
               logger.error("e.getClass(): "+e.getClass());
              // throw new HibernateException(e.getMessage());
            }
        }

This is the stackTrace of the exception I am getting.

org.hibernate.exception.JDBCConnectionException: Cannot open connection
        at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
        at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:426)
        at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)
        at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:119)
        at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:57)
        at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1326)
        at com.arosys.hibernateDao.AbstractDao.startOperation(AbstractDao.java:184)
        at com.arosys.hibernateDao.AbstractDao.findAll(AbstractDao.java:150)
        at com.arosys.beansDao.JobHierarchyDao.findAll(JobHierarchyDao.java:20)
        at org.ArosysLogin.server.GWTJobImpl.getJobHierarchy(GWTJobImpl.java:416)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:569)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248)
        at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:开发者_如何学Go127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:861)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1584)
        at java.lang.Thread.run(Thread.java:662)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.

Just guessing since there isn't enough information (type and message of the exception):

• Connection fails due to flaky database/network connection

• do you commit your transactions? I'm not sure, but Hibernate might complain if you try to start a transaction twice.

UPDATE based on the call stack.

This seems to be a problem with the database. check out the various results for googling "com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure"

This one might help: https://serverfault.com/questions/89955/unable-to-connect-to-mysql-through-jdbc-connector-through-tomcat-or-externally

Are you sure your connections get closed after usage? I can imagine the database denying access after so many connections are opened. Checking the logs of your database might help as well.

1. Set ValidateConnectionOnBorrow to true
2. and add a validation query for SQLForValidateConnection
3. Set autoReconnect to true for jdbc URL

either by Server connection pool configuration or connection pool configuration.

I assume(from the stack trace) that you are using MySQL,Hibernate with either JBoss or Tomcat.

Let me know in case you face any problem, I faced the same long ago.