使用hibernate连接mysql自动中断的问题

关键字:   hibernate, mysql, c3p0    

数据库为mysql，客户端使用hibernate进行连接，结果长时间没有数据访问的话，重新访问数据库就会报错：

java 代码

org.hibernate.exception.JDBCConnectionException: could not execute query
at 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.CommunicationsException
MESSAGE: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.net.SocketException
MESSAGE: Broken pipe

STACKTRACE:

java.net.SocketException: Broken pipe
at java.net.SocketOutputStream.socketWrite0(Native Method)
......
** END NESTED EXCEPTION **

查阅相关文档，造成报错的原因在于：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。

解决的方法有3种：

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

使用c3p0解决上面问题的配置如下：

   <!-- C3P0 Connection Pool-->

java 代码

<!-- C3P0 Connection Pool-->
    "c3p0.min_size">10
    "c3p0.max_size">100
    "c3p0.timeout">10
    "c3p0.acquireRetryAttempts">30

    "c3p0.acquireIncrement">5

    <!--<span class="comment">//set to something much less than wait_timeout, prevents connections from going stale-->
    "c3p0.idleConnectionTestPeriod">300

    "c3p0.initialPoolSize">20
    "c3p0.maxPoolSize">100
    <!--<span class="comment">//set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out -->
    "c3p0.maxIdleTime">300
    "c3p0.maxStatements">50
    "c3p0.minPoolSize">10