做网站工作室名字建设企业网站需要注意的问题

QreryRunner是Dbutils的核心类之一，它显著的简化了SQL查询，并与ResultSetHandler协同工作将使编码量大为减少。

注意事项

1. 使用QreryRunner必须保证实体类的变量名，和sql语句中要查找的字段名必须相同，否则查询

不到数据,会出现NullPointerException异常

此时sql语句名和数据库名不一致

public Manager selectManagerByName(String name) throws SQLException {QueryRunner qr = new QueryRunner(JDBCUtils.getDataSource());String sql = "select mgr_id,login_name,login_pwd ,mgr_name " +",mgr_gender ,mgr_tel ,mgr_email ,mgr_qq ,create_time  " +"from tb_managers where login_name=?";Object[] args = {name};return qr.query(sql,new BeanHandler<>(Manager.class),args);
}

 异常

加上别名后可正常查询

public Manager selectManagerByName(String name) throws SQLException {QueryRunner qr = new QueryRunner(JDBCUtils.getDataSource());String sql = "select mgr_id mgrId ,login_name loginName,login_pwd loginPwd,mgr_name mgrName" +",mgr_gender mgrGender,mgr_tel mgrTel,mgr_email mgrEmail,mgr_qq mgrQQ,create_time createTime " +"from tb_managers where login_name=?";Object[] args = {name};return qr.query(sql,new BeanHandler<>(Manager.class),args);
}