C3p0數據源ComboPooledDataSource的close方法

使用定時器：c3p0將拋出，

com.mchange.v2.c3p0.impl.NewProxyConnection@1953895
Exception in thread "main" Java.sql.SQLException: com.mchange.v2.c3p0.ComboPooledDataSource [ java.beans.IntrospectionException: java.lang.reflect.InvocationTargetException [numThreadsAwaitingCheckoutDefaultUser] ] has been closed() -- you can no longer use it.
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.assertCpds(AbstractPoolBackedDataSource.java:495)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getPoolManager(AbstractPoolBackedDataSource.java:507)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
at Main.getConnection(Main.java:21)
at Main.main(Main.java:35)

緣由：數據源被關閉了。

ds = new ComboPooledDataSource();