Question

我在我的网络应用程序中使用hibernate，当我在以下情况下遇到异常时：

Transaction tx=session.beginTransaction();

它偶尔会发出异常，我正在重新加载SessionFactory，同时捕获异常然后运行正常。

当我再次重新加载SessionFactory时它正在工作。

这是我的代码段：

 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());
            }
        }

这是我得到的异常的stackTrace。

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:127)
        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.

Answer 1

只是猜测因为没有足够的信息（例外的类型和消息）：

由于数据库/网络连接不稳定导致连接失败
你提交交易吗？我不确定，但如果你尝试两次启动交易，Hibernate可能会抱怨。

根据调用堆栈更新。

这似乎是数据库的问题。查看google搜索的各种结果“com.mysql.jdbc.exceptions.jdbc4.CommunicationsException：Communications link failure”

这个可能会有所帮助：https://serverfault.com/questions/89955/unable-to-connect-to-mysql-through-jdbc-connector-through-tomcat-or-externally

您确定您的连接在使用后会关闭吗？我可以想象数据库在打开这么多连接后拒绝访问。检查数据库的日志也可能有所帮助。

Answer 2

将ValidateConnectionOnBorrow设为true
并为SQLForValidateConnection
将jdbc网址

autoReconnect

通过服务器连接池配置或连接池配置。

我假设（从堆栈跟踪）你正在使用MySQL，Hibernate使用JBoss或Tomcat。

如果你遇到任何问题，请告诉我，很久以前我也面临同样的问题。

beginTransaction中的异常

2 个答案: