using the Connector/J connection property 'autoReconnect=true' to avoid this problem

报错信息：
com.mysql.jdbc.CommunicationsException: The last packet successfully received from the server was58129 seconds ago.The last packet sent successfully to the server was 58129 seconds ago, which is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.





查了一下，原来是mysql超时设置的问题
如果连接闲置8小时 (8小时内没有进行数据库操作), mysql就会自动断开连接, 要重启tomcat.


解决办法：
一种. 如果不用hibernate的话, 则在　connection url中加参数: autoReconnect=true

jdbc.url=jdbc:mysql://ipaddress:3306/database?autoReconnect=true&autoReconnectForPools=true


二种。用hibernate的话, 加如下属性:
<property name="connection.autoReconnect">true</property>
<property name="connection.autoReconnectForPools">true</property>
<property name="connection.is-connection-validation-required">true</property>



三。要是还用c3p0连接池:
<property name="hibernate.c3p0.acquire_increment">1</property>
<property name="hibernate.c3p0.idle_test_period">0</property>
<property name="hibernate.c3p0.timeout">0</property>
<property name="hibernate.c3p0.validate">true</property>



　四。修改mysql配置文件属性：

MySQL服务器默认的“wait_timeout”是28800秒即8小时，意味着如果一个连接的空闲时间超过8个小时，MySQL将自动断开该连接，而连接池却认为该连接还是有效的(因为并未校验连接的有效性)，当应用申请使用该连接时，就会导致上面的报错。

只能修改MySQL的参数了，wait_timeout最大为31536000即1年，在my.cnf中加入：


[mysqld]
wait_timeout=31536000
interactive_timeout=31536000

重启生效，需要同时修改这两个参数。

半个月
wait_timeout=1314000
interactive_timeout=1314000