当使用后台线程完成更新查询时，我正在观察以下异常。这个异步清理线程是从也执行数据库操作的主线程中调用的。提交主线程的事务后，将调用后台线程。我不确定连接如何关闭。主线程没有关闭连接，而只是在提交事务。我多次尝试相同的流，但是我只是间歇性地看到失败，所以不确定是什么引起了问题。
javax.persistence.PersistenceException: org.hibernate.TransactionException: JDBC begin transaction failed:
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1387)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1310)
at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:1397)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:62)
at com.google.inject.internal.cglib.proxy.$MethodProxy.invokeSuper(MethodProxy.java:228)
at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:75)
at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:75)
at com.google.inject.internal.InterceptorStackCallback.intercept(InterceptorStackCallback.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:95)
at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:154)
at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:80)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.hibernate.TransactionException: JDBC begin transaction failed:
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:76)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:160)
at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1426)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:59)
... 20 more
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.Util.getInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:898)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:887)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:861)
at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1184)
at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1179)
at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4755)
at com.mchange.v2.c3p0.impl.NewProxyConnection.setAutoCommit(NewProxyConnection.java:1059)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:72)
... 23 more
我还在日志中观察到以下堆栈跟踪
2018-08-10T06:29:06.884-0700 c.m.v.r.BasicResourcePool [C3P0PooledConnectionPoolManager[identityToken->2s2zx19x9yds8h4a2bso|f2a1813, dataSourceName->DEFAULT]-AdminTaskTimer] [null] - A checked-out resource is overdue, and will be destroyed: com.mchange.v2.c3p0.impl.NewPooledConnection@46adc151
2018-08-10T06:29:06.884-0700 c.m.v.r.BasicResourcePool [C3P0PooledConnectionPoolManager[identityToken->2s2zx19x9yds8h4a2bso|f2a1813, dataSourceName->DEFAULT]-AdminTaskTimer] [null] - Logging the stack trace by which the overdue resource was checked-out.
java.lang.Exception: DEBUG STACK TRACE: Overdue resource check-out stack trace.
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:588)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:758)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:685)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140)
at org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:84)
at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:292)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:214)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:157)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:67)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:160)
at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:1426)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:59)