Hibernate无法提取ResultSet异常

我在Tomcat服务器上部署了一个GWT应用程序.一切都很好,但有时我得到以下例外:

org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
        at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:389)
        at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:579)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:265)
        at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:305)
        at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:644)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:301)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:136)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:74)
        at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:526)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1017)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:652)
        at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1575)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1533)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:744)
Caused by: org.hibernate.exception.JDBCConnectionException: could not extract ResultSet
        at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:132)
        at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
        at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
        at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
        at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:61)
        at org.hibernate.loader.Loader.getResultSet(Loader.java:2040)
        at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1837)
        at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:1816)
        at org.hibernate.loader.Loader.doQuery(Loader.java:900)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
        at org.hibernate.loader.Loader.doList(Loader.java:2526)
        at org.hibernate.loader.Loader.doList(Loader.java:2512)

如您所见,我使用Hibernate通过以下配置管理我的数据库:

        com.mysql.jdbc.Driver

        jdbc:mysql://server:3306/db
        username

        password

        
        1
        15
        300
        50
        3000

        
        com.ohapp.webtattoon.server.service.Mysql5BitBooleanDialect

        
        thread

        
        org.hibernate.cache.NoCacheProvider

        
        false

        
        validate

我不知道为什么会这样.我真的很感激一些帮助.

谢谢