quartz定时报错，连接失效出现问题

异常：

[2017-11-23 13:57:11] [WARN ] [com.mchange.v2.c3p0.impl.NewPooledConnection:425] - [c3p0] A PooledConnection that has already signalled a Connection error is still in use!

[2017-11-23 13:57:11] [WARN ] [com.mchange.v2.c3p0.impl.NewPooledConnection:426] - [c3p0] Another error has occurred [ com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed. ] which will not be reported to listeners!
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:423)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.Util.getInstance(Util.java:387)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:917)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:896)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:885)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:860)
at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1235)
at com.mysql.jdbc.ConnectionImpl.checkClosed(ConnectionImpl.java:1230)
at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4833)
at com.mchange.v2.c3p0.impl.NewProxyConnection.setAutoCommit(NewProxyConnection.java:881)
at org.quartz.impl.jdbcjobstore.AttributeRestoringConnectionInvocationHandler.restoreOriginalAtributes(AttributeRestoringConnectionInvocationHandler.java:141)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.cleanupConnection(JobStoreSupport.java:3600)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.doRecoverMisfires(JobStoreSupport.java:3206)
at org.quartz.impl.jdbcjobstore.JobStoreSupport$MisfireHandler.manage(JobStoreSupport.java:3935)
at org.quartz.impl.jdbcjobstore.JobStoreSupport$MisfireHandler.run(JobStoreSupport.java:3956)

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Mysql服务器默认的“wait_timeout”是8小时，也就是说一个connection空闲超过8个小时，Mysql将自动断开该connection。这就是问题的所在，在C3P0 pools中的connections如果空闲超过8小时，Mysql将其断开，而C3P0并不知道该connection已经失效，如果这时有Client请求connection，C3P0将该失效的Connection提供给Client，将会造成上面的异常。

分析过程：

而c3p0属性

<!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->
<property name="maxIdleTime">60</property>

quartz定时任务使用的是默认是maxIdleTime=0，永不丢弃。

从日志文件打印quartz数据库配置信息来看

characterEncoding = UTF - 8 & useSSL = TRUE,
 lastAcquisitionFailureDefaultUser -> NULL,
 maxAdministrativeTaskTime -> 0,
 maxConnectionAge -> 0,
 maxIdleTime -> 0,
 maxIdleTimeExcessConnections -> 0,
 maxPoolSize -> 100,
 maxStatements -> 0,
 maxStatementsPerConnection -> 120,

解决办法：1.查看源码看是否加上需要加上最大空闲时间 设置为60s

quartz的属性配置是discardIdleConnectionsSeconds

org.quartz.dataSource.myDS.discardIdleConnectionsSeconds：60

2.validationQuery:每次返回连接时执行数据库sql查询到池中确保它仍然有效。

org.quartz.dataSource.myDS.validationQuery：SELECT 1 FROM DUAL