JDBC使用QreryRunner简化SQL查询注意事项

美式要加冰2024-05-23 8:17

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

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

java 复制代码

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

java 复制代码

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);
}