NHibernate 中的静态查找

发布于 2024-07-29 11:41:15 字数 791 浏览 5 评论 0原文

我想在 NHibernate 中使用一些预定义的查找，而不需要对数据库进行往返。

基本上我想要这样的代码：

public class Countries
{
  static Countries() {
    Australia = new Country
      {
          Id = 14,
          Description = "Australia"
      }
  }
  public static Country Austrlia { get; protected set }
}

然后编写以下代码片段：

address.Country = Countries.Australia;// Snippet1
if (address.Country == Countries.Australia) { // Snippet2
  // Do something
}

所以我会重写 Equals、GetHashCode 甚至重载运算符 == 和 != 用于 Country 类查找。

仅当具有给定 ID 的国家/地区尚未加载到内存中时，Snippet1 才起作用。否则，它会抛出 NonUniqueObjectException ，表示具有给定 Id 的对象已在内存中。

为了解决这个问题，我必须驱逐加载的国家/地区，然后分配查找值。这感觉不对，我不确定再次执行国家/地区查找查询时会发生什么。

那么问题是：如何在NHibernate中维护静态查找类？

谢谢，德米特里。

原文

I want to use some of predefined lookups without roundrips to Database in NHibernate.

Basically I would like to have code like this:

public class Countries
{
  static Countries() {
    Australia = new Country
      {
          Id = 14,
          Description = "Australia"
      }
  }
  public static Country Austrlia { get; protected set }
}

Then write this code snippets:

address.Country = Countries.Australia;// Snippet1
if (address.Country == Countries.Australia) { // Snippet2
  // Do something
}

So I do override Equals, GetHashCode and even overload operators == and != for Country class lookup.

The Snippet1 works ONLY if the Country with given Id has not been loaded into memory.
Otherwise it throws NonUniqueObjectException saying the object with given Id is already in memory.

To workaraound this I have to evict the loaded country and then assign the lookup value.
This feels wrong and I'm not sure what will happen when the query for Country lookup will be executed again.

So the question is: How to maintain static lookup classes in NHibernate?

Thanks,
Dmitriy.

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戴着白色围巾的女孩 2024-08-05 11:41:17

NHibernate 似乎无法处理逻辑上相同（但实例不同）的 2 个对象。
因此，与其将“静态查找”与数据库查找混合在一起，不如只使用其中之一。

就我而言 - 存储在数据库中的查找。但为了避免仅仅为了获取对象而往返数据库，只需要使用 Load 而不是 Get：

address.Country = Session.Load<Country>(CountryIds.Australia); // This does not hit DB
address.Country = Session.Get<Country>(CountryIds.Australia); // This DOES hit DB

It seems NHibernate cannot handle 2 objects logically the same (but different instances).
So instead of mixing "static lookup" with Database lookups it is better to only use one of them.

In my case - lookups stored in the database. BUT to avoid roundtrip to the database just for the sake of obtaining the object it is only needed to use Load instead of Get:

address.Country = Session.Load<Country>(CountryIds.Australia); // This does not hit DB
address.Country = Session.Get<Country>(CountryIds.Australia); // This DOES hit DB

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