无法自动获取数据库类型，怎么改？



```java

Caused by: org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.RuntimeException: 无法自动获取数据库类型，请通过 dialect 参数指定!
### Cause: java.lang.RuntimeException: 无法自动获取数据库类型，请通过 dialect 参数指定!
    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
    at com.sun.proxy.$Proxy140.selectList(Unknown Source)
    at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230)
    at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
    at com.sun.proxy.$Proxy141.selectByExample(Unknown Source)
    ... 136 common frames omitted
Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.RuntimeException: 无法自动获取数据库类型，请通过 dialect 参数指定!
### Cause: java.lang.RuntimeException: 无法自动获取数据库类型，请通过 dialect 参数指定!
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
    ... 142 common frames omitted
Caused by: java.lang.RuntimeException: 无法自动获取数据库类型，请通过 dialect 参数指定!
    at com.github.pagehelper.util.SqlUtil.getDialect(SqlUtil.java:256)
    at com.github.pagehelper.util.SqlUtil.doIntercept(SqlUtil.java:109)
    at com.github.pagehelper.util.SqlUtil.intercept(SqlUtil.java:84)
    at com.github.pagehelper.PageHelper.intercept(PageHelper.java:50)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:61)
    at com.sun.proxy.$Proxy213.query(Unknown Source)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
    ... 148 common frames omitted