SQLException: com.mchange.v2.c3p0.ComboPooledDataSource [ java.beans.IntrospectionException: java.lang.reflect.InvocationTargetException [numThreadsAwaitingCheckoutDefaultUser] ] has been closed()

问题：Could not get JDBC Connection; nested exception is 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 异常

原因：由于连接池设置breakAfterAcquireFailure参数为true,出现服务网络不稳定时导致

解决方法：breakAfterAcquireFailure ：true表示pool向数据库请求连接失败后标记整个pool为block并close，就算后端数据库恢复正常也不进行重连，客户端对pool的请求都拒绝掉。false表示不会标记 pool为block，新的请求都会尝试去数据库请求connection。默认为false。因此，如果想让数据库和网络故障恢复之后，pool能继续请求正常资源必须把此项配置设为false