报错如下

The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Unknown system variable 'query_cache_size'
    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:96) ~[mybatis-spring-2.0.6.jar:2.0.6]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:441) ~[mybatis-spring-2.0.6.jar:2.0.6]
    at com.sun.proxy.$Proxy113.selectList(Unknown Source) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:224) ~[mybatis-spring-2.0.6.jar:2.0.6]
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.binding.MapperProxy$PlainMethodInvoker.invoke(MapperProxy.java:145) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:86) ~[mybatis-3.5.7.jar:3.5.7]
    at com.sun.proxy.$Proxy114.selectTbThroughExperimentsList(Unknown Source) ~[na:na]

### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Unknown system variable 'query_cache_size'
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) ~[mybatis-3.5.7.jar:3.5.7]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:427) ~[mybatis-spring-2.0.6.jar:2.0.6]
    ... 82 common frames omitted
Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Unknown system variable 'query_cache_size'
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:83) ~[spring-jdbc-5.3.12.jar:5.3.12]
    at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:80) ~[mybatis-spring-2.0.6.jar:2.0.6]
    at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:67) ~[mybatis-spring-2.0.6.jar:2.0.6]
    at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) ~[mybatis-3.5.7.jar:3.5.7]
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) ~[mybatis-3.5.7.jar:3.5.7]
    at com.github.pagehelper.PageInterceptor.intercept(PageInterceptor.java:132) ~[pagehelper-5.3.0.jar:na]
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:62) ~[mybatis-3.5.7.jar:3.5.7]
    at com.sun.proxy.$Proxy166.query(Unknown Source) ~[na:na]
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:151) ~[mybatis-3.5.7.jar:3.5.7]
    ... 89 common frames omitted
Caused by: java.sql.SQLException: Unknown system variable 'query_cache_size'
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:545) ~[mysql-connector-java-6.0.6.jar:6.0.6]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:513) ~[mysql-connector-java-6.0.6.jar:6.0.6]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:115) ~[mysql-connector-java-6.0.6.jar:6.0.6]
    at com.mysql.cj.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:1983) ~[mysql-connector-java-6.0.6.jar:6.0.6]

解决方案：

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.27</version>
</dependency>

原来的

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>6.0.6</version>
</dependency>

造成原因是版本太低，mysql从5.7.20就不用了query cache。