Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.sqlnestedException: Cannot create PoolableConnectionFactory (UnkNown system variable 'query_cache_size') ### The error may exist in file [/Volumes/mac/Eclipse Project/Tomcat_version/apache-tomcat-9.0.21/webapps/chuan_zang_help/WEB-INF/classes/cn/ydyfc/chuan_zang_help/mapper/AdminMapper.xml] ### The error may involve cn.ydyfc.chuan_zang_help.dao.AdminMapper.selectAllAdmins ### The error occurred while executing a query ### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.sqlnestedException: Cannot create PoolableConnectionFactory (UnkNown system variable 'query_cache_size')] with root cause java.sql.sqlException: UnkNown system variable 'query_cache_size' at com.MysqL.jdbc.sqlError.createsqlException(sqlError.java:964) at com.MysqL.jdbc.MysqLIO.checkerrorPacket(MysqLIO.java:3973) at com.MysqL.jdbc.MysqLIO.checkerrorPacket(MysqLIO.java:3909) at com.MysqL.jdbc.MysqLIO.sendCommand(MysqLIO.java:2527)
错误提示：Cannot create PoolableConnectionFactory (UnkNown system variable 'query_cache_size')
原因：由于MysqL驱动包的版本过低导致这个问题的发生意思是query cache在MysqL5.7.20就已经过时了，而在MysqL8.0之后就已经被移除了。
我改成8以上才可以了。
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