最佳实践 - 通过静态字段获取 grails 中的域对象？
因此，我们的一些 grails 对象（参考数据）有独特的“代码”，当我们想要检索它们时，我们通过使用它们的静态代码调用它们来实现：
Currency.findByCode(Currency.DOLLAR)
也许我完全错了，但这似乎是一个非常好的方法。检索对象的冗长且非常规的方式（特别是当您必须为多个对象执行多次时）。
是否有更可接受的方法（也许在某处引用了对象本身）？如果这是最好的方法，那么这是一个可以接受的答案。谢谢。
So we have unique 'codes' for some of our grails objects (ref data), and when we want to retrieve them, we do so by calling them with their static code:
Currency.findByCode(Currency.DOLLAR)
Perhaps I'm completely wrong, but this seems like a very verbose and non-groovy way of retrieving objects (especially when you have to do it multiple times, for multiple objects).
Is there a more accepted approach (maybe having a reference to the object itself somewhere)? If this is the best way to do it, that is an acceptable answer. Thanks.
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（2）
使用静态变量，您可以做的另一件事是使用静态导入来缩短代码（这实际上是 Java 的一部分，但直到我转向 groovy 才找到它）：
如果您 类顶部的CurrencyType（可能是保存您定义的各种类型的货币的枚举）：
在代码中，您不再需要为所有引用添加前缀
CurrencyType，您可以这样做：如果不需要更改，您还可以向您的货币类添加一个辅助方法来检索它：
这将允许您在其他代码中使用
Currency.dollar。在这些类中，您还可以使用静态导入来引用dollar：One other thing that you could do to shorten up the code if you use static variables is to use static imports (this is actually part of Java, but I didn't find it till I moved to groovy):
If you do a static import of CurrencyType (potentially an enum holding the various types of Currency that you've defined) at the top of your class:
Down in your code, you no longer need to prefix all of the references with
CurrencyType, you can just do:If they don't need to change, you could also add a helper method to your Currency class to retrieve it:
That would let you use
Currency.dollarin your other code. In those classes, you could also use a static import there to just refer todollar:这取决于。这看起来像是参考数据。如果参考数据永远不会改变，我根本不会使用持久层——我会编写一堆静态变量作为静态参考数据。
如果您希望能够更改参考数据而不重新部署，最实用的方法是从数据库加载它们。您将拥有某种类型的管理屏幕，您可以在其中操作数据。您可以使用像 ehcache 这样的二级缓存来限制持久层实际访问数据库的数量——这样您可以获得非常好的性能。请参阅用户指南第 5.5.2.2 节。
但是，使用当前的方法，您必须根据参考数据的更改进行重新部署，因为需要对Currency.DOLLAR 进行编码。最好不必这样做。
It depends. This seems like reference data. If the reference data is never gonna change, I wouldn't use the persistence layer at all -- I would code up a bunch of static variables that are the static reference data.
If you want to be able to change your reference data without redeploying, the most practical way would be to load them from the db. You would have some type of admin screen where you could manipulate the data. You would use 2nd level cache like ehcache to limit how much the persistence layer actually hit the db -- you can get really good performance this way. See section 5.5.2.2 of the user guide.
However, with your current approach you would have to redeploy on a change in your reference data, because the Currency.DOLLAR need to be coded in. It would probably be nice to not have to do that.