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.

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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.?

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解决办法：

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??? 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

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??? 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>

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??? 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">