MyBatis异常：No operations allowed after connection closed

MyBatis连接MySQL报异常：No operations allowed after connection closed.Connection was i
连接池报错
myBatis连接MySQL报异常：No operations allowed after connection closed.Connection was implicitly closed

异常信息

org.hibernate.exception.JDBCConnectionException: could not execute queryat org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43).......Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed due to underlying exception/error:** BEGIN NESTED EXCEPTION **com.mysql.jdbc.CommunicationsExceptionMESSAGE: Communications link failure due to underlying exception:** BEGIN NESTED EXCEPTION **java.net.SocketExceptionMESSAGE: Broken pipeSTACKTRACE:java.net.SocketException: Broken pipeat java.net.SocketOutputStream.socketWrite0(Native Method)......

原因分析

查看了Mysql的文档，以及Connector/J的文档以及在线说明发现，出现这种异常的原因是：

　　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。
解决方案

解决的方法有3种：

增加 wait_timeout 的时间。减少 Connection pools 中 connection 的 lifetime。测试 Connection pools 中 connection 的有效性。

当然最好的办法是同时综合使用上述3种方法，下面就 DBCP、C3P0 和 simple jdbc dataSource 分别做一说明，假设 wait_timeout 为默认的8小时

DBCP 增加以下配置信息:

validationQuery = "select 1"testWhileIdle = "true"//some positive integertimeBetweenEvictionRunsMillis = 3600000//set to something smaller than 'wait_timeout'minEvictableIdleTimeMillis = 18000000//if you don't mind a hit for every getConnection(), set to "true"testOnBorrow = "true"

C3P0 增加以下配置信息:

//获取connnection时测试是否有效testConnectionOnCheckin = true//自动测试的table名称automaticTestTable=C3P0TestTable//set to something much less than wait_timeout, prevents connections from going staleidleConnectionTestPeriod = 18000//set to something slightly less than wait_timeout, preventing 'stale' connections from being handed outmaxIdleTime = 25000//if you can take the performance 'hit', set to "true"testConnectionOnCheckout = true

simple jdbc dataSource 增加以下配置信息:

Pool.PingQuery = select 1Pool.PingEnabled = truePool.PingConnectionsOlderThan = 0//对于空闲的连接一个小时检查一次Pool.PingConnectionsNotUsedFor = 3600000

其他方案（不推荐）

　　对于 MySQL5 之前的版本，如 Mysql4.x，只需要修改连接池配置中的 URL，添加一个参数：autoReconnect=true(如jdbc:mysql://hostaddress:3306/schemaname?autoReconnect=true)，如果是 MySQL5 及以后的版本，则需要修改 my.cnf(或者my.ini) 文件，在 [mysqld] 后面添加上：
wait_timeout = n
interactive-timeout = n

其中 n 为服务器关闭交互式连接前等待活动的秒数。可是就部署而言每次修改 my.ini 比较麻烦，而且 n 等于多少才是合适的值呢？ 所以并不推荐这个解决办法。)