修复分页插件获取数据库类型问题.

https://github.com/baomidou/mybatis-plus/issues/2172

mybatis-plus-extension/src/main/java/com/baomidou/mybatisplus/extension/plugins/PaginationInterceptor.java

@@ -211,8 +211,8 @@ public class PaginationInterceptor extends AbstractSqlParserHandler implements I
                 return null;
             }
         }
-        DbType dbType = Optional.ofNullable(this.dbType).orElse(JdbcUtils.getDbType(connection.getMetaData().getURL()));
-        IDialect dialect = Optional.ofNullable(this.dialect).orElse(DialectFactory.getDialect(dbType));
+        DbType dbType = this.dbType == null ? JdbcUtils.getDbType(connection.getMetaData().getURL()) : this.dbType;
+        IDialect dialect = Optional.ofNullable(this.dialect).orElseGet(() -> DialectFactory.getDialect(dbType));
         String buildSql = concatOrderBy(originalSql, page);
         DialectModel model = dialect.buildPaginationSql(buildSql, page.offset(), page.getSize());
         Configuration configuration = mappedStatement.getConfiguration();