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)
錯誤提示：Cannot create PoolableConnectionFactory (Unknown system variable 'query_cache_size')
原因：由於mysql驅動包的版本過低導致這個問題的發生意思是query cache在MySQL5.7.20就已經過時了，而在MySQL8.0之后就已經被移除了。
我改成8以上才可以了。