csdn有一个，要收费，研究后原因如下，是 mysql不支持 SQL catalogs and schema， 解决方式就是去掉 这两个字段，同时在jdbcConnection中设置nullCatalogMeansCurrent属性为true。 手册如下

MySql does not properly support SQL catalogs and schema. If you run the create schema command in MySql, it actually creates a database - and the JDBC driver reports it back as a catalog. But MySql syntax does not support the standard catalog..table SQL syntax.

For this reason, it is best to not specify either catalog or schema in generator configurations. Just specify table names and specify the database in the JDBC URL.

If you are using version 8.x of Connector/J you may notice that the generator attempts to generate code for tables in the MySql information schemas (sys, information_schema, performance_schema, etc.) This is probably not what you want! To disable this behavior, add the property "nullCatalogMeansCurrent=true" to your JDBC URL.

For example:

    <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost/my_schema"userId="my_user" password="my_password"><property name="nullCatalogMeansCurrent" value="true" /></jdbcConnection>