使用 NHibernate/ActiveRecord 自动模式验证

发布于 2024-08-02 19:27:51 字数 398 浏览 1 评论 0原文

假设我有一个产品表，其中包含以下列：ID、名称、价格并使用NHibernate（或ActiveRecord）将表映射到POCO：

public class Product
{
    public virtual long Id { get; set; }
    public virtual string Name { get; set; }
    public virtual double Price { get; set; }
}

现在，如果有一天有一个名为ShipmentPrice的新列（我们假设它也是双倍的）将添加到产品表中，有什么方法可以自动知道这一点吗？

自动地说，我的意思是添加代码来执行此操作或获得异常？（我假设我无法控制表的列或无法控制提前知道表架构的任何更改）

原文

Let's assume I have a table of Products with columns: Id, Name, Price
and using NHibernate (or ActiveRecord) I map the table to the POCO:

public class Product
{
    public virtual long Id { get; set; }
    public virtual string Name { get; set; }
    public virtual double Price { get; set; }
}

Now if someday a new column named ShipmentPrice (let's assume it's double too)
will be added to the Products table, is there any way I can automatically know that?

For saying automatically I mean adding code to do that or getting an exception?
(I assume I don't have control on the columns of the table or a way to
know of any changes to the table's schema in advance)

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铜锣湾横着走 2024-08-09 19:27:51

你没记错，毛里西奥。以下代码显示了如何创建或更新架构。当 Validate() 引发异常时，更新将运行。当某个字段在数据库中可用但在配置中不可用时，不会引发异常。拥有额外的字段是完全合法的：我希望您不希望它们被删除？这可能会造成巨大的损害...

以下代码显示了测试、创建、验证和更新，每个步骤都有正确的异常处理。代码已简化，但它应该让您了解如何进行验证。

此代码有助于以实体为中心 (POCO) ORM 配置，您可以在其中向类添加字段，并且它将自动在数据库中更新。不是以表为中心，以字段为主导。

// executes schema script against database
private static void CreateOrUpdateSchema(Configuration config)
{
    // replace this with your test for existence of schema
    // (i.e., with SQLite, you can just test for the DB file)
    if (!File.Exists(DB_FILE_NAME))
    {
        try
        {
            SchemaExport export = new SchemaExport(config);
            export.Create(false, true);
        }
        catch (HibernateException e)
        {
            // create was not successful
            // you problably want to break out your application here
            MessageBox.Show(
                String.Format("Problem while creating database: {0}", e),
                "Problem");
        }
    }
    else
    {

        // already something: validate
        SchemaValidator validator = new SchemaValidator(config);
        try
        {
            validator.Validate();
        }
        catch (HibernateException)
        {
            // not valid, try to update
            try
            {
                SchemaUpdate update = new SchemaUpdate(config);
                update.Execute(false, true);
            }
            catch (HibernateException e)
            {
                // update was not successful
                // you problably want to break out your application here
                MessageBox.Show(
                    String.Format("Problem while updating database: {0}", e),
                    "Problem");
            }
        }
    }
}

——阿贝尔——

You do recall correctly, Mauricio. The following code shows how you can create or update a schema. The update will run when Validate() raises an exception. No exception will be thrown when a field is available in the database but not in the configuration. It is perfectly legal to have extra fields: you don't want them to be deleted, I hope? That could cause tremendous damage...

The following code shows Test, Create, Validate and Update, each step with the proper exception handling. The code is simplified, but it should give you a handle on how to do a validation.

This code helps with Entity-centric (POCO) ORM configurations, where you can add a field to your class and it will automatically be updated in the database. Not with table-centric, where fields are leading.

// executes schema script against database
private static void CreateOrUpdateSchema(Configuration config)
{
    // replace this with your test for existence of schema
    // (i.e., with SQLite, you can just test for the DB file)
    if (!File.Exists(DB_FILE_NAME))
    {
        try
        {
            SchemaExport export = new SchemaExport(config);
            export.Create(false, true);
        }
        catch (HibernateException e)
        {
            // create was not successful
            // you problably want to break out your application here
            MessageBox.Show(
                String.Format("Problem while creating database: {0}", e),
                "Problem");
        }
    }
    else
    {

        // already something: validate
        SchemaValidator validator = new SchemaValidator(config);
        try
        {
            validator.Validate();
        }
        catch (HibernateException)
        {
            // not valid, try to update
            try
            {
                SchemaUpdate update = new SchemaUpdate(config);
                update.Execute(false, true);
            }
            catch (HibernateException e)
            {
                // update was not successful
                // you problably want to break out your application here
                MessageBox.Show(
                    String.Format("Problem while updating database: {0}", e),
                    "Problem");
            }
        }
    }
}

-- Abel --

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