MySQL连接超时自动断开连接问题

描述：

    用mybatis2.3.5实现做应用时，程序中报以下错误：
    com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 
    The last packet successfully received from the server was 79,221,885 milliseconds ago. 
    The last packet sent successfully to the server was 79,221,885 milliseconds ago. 
    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. 

解释及解决办法： 

    如果连接闲置8小时 (mysql的wait_timeout参数默认时间), mysql就会自动断开连接, 得刷新应用才行. 
    不用hibernate的话, connection url加参数: autoReconnect=true  
    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> 
    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>

例：jdbc.url=jdbc:mysql://localhost:3306/yht_wxt?zeroDateTimeBehavior=convertToNull&useUnicode=True&characterEncoding=utf8&autoReconnect=true&autoReconnectForPools=true