现象: mybatis Cause: com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure

解决:

方法一：登陆mysql:

show global variables like 'wait_timeout';
show global variables like 'interactive_timeout';

set global wait_timeout=864000;
set global interactive_timeout=864000;

方法二：mybatis settings设置:

<settings>
    <setting name="cacheEnabled" value="true"/>
    <setting name="lazyLoadingEnabled" value="true"/>
    <setting name="multipleResultSetsEnabled" value="true"/>
    <setting name="useColumnLabel" value="true"/>
    <setting name="useGeneratedKeys" value="false"/>
    <setting name="autoMappingBehavior" value="PARTIAL"/>
    <setting name="autoMappingUnknownColumnBehavior" value="WARNING"/>
    <setting name="defaultExecutorType" value="SIMPLE"/>
    <setting name="defaultStatementTimeout" value="864000"/>
    <setting name="defaultFetchSize" value="50"/>
    <setting name="safeRowBoundsEnabled" value="false"/>
    <setting name="mapUnderscoreToCamelCase" value="false"/>
    <setting name="localCacheScope" value="SESSION"/>
    <setting name="jdbcTypeForNull" value="OTHER"/>
    <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/>
</settings>