参考数据模式
与此线程类似，但不完全一样：如何以线程安全方式缓存信息
处理“参考数据”的常用模式是什么？应用程序经常读取的数据，通常在数据库或属性文件中外部化，但更新频率很低（几天、几周） ，月）？ 当数据更新时，它会在外部更新。
这通常是一个单例，我可以用 DAO 注入它，从而能够管理它自己的内容吗？ 我喜欢在该服务上公开一个刷新（）方法的想法，该方法将强制刷新（即通过 MBean - 这样我就不必退回应用程序）。
从另一个 SO 线程来看，听起来人们可能会在必要时实例化 DAO，并在该级别透明地缓存。
我有点喜欢单例服务的想法，要么注入一个从数据库加载数据的真实 DAO，要么注入一个返回硬编码响应的模拟/测试替身。 然而，如果我通过 java 枚举将服务实现为单例，这使得通过 Spring 连接它会出现一些问题。
那么，其他人通常如何处理参考数据呢？ 随意查询但在幕后有缓存？ 或者单独的内存服务？
Similar to this thread, but not exactly: How To Cache Information In A Threadsafe Manner
What is the usual pattern for dealing with "reference data" - data that is frequently read by an application, usually externalized in a database or properties file, but updated very infrequently (days, weeks, months)? When the data is updated, it would be updated externally.
Would this normally be a singleton that I could inject with a DAO and would thus be able to manage its own contents? I like the idea of exposing a refresh() method on this service that would force a refresh (i.e., through an MBean - so I wouldn't have to bounce the application).
From the other SO thread, it sounds like people might just instantiate the DAO's whenever necessary and cache transparently at that level.
I kind of like the idea of the singleton service being injected with either a real DAO that loads data from the database, or else a mock/test-double that returns a hard-coded response. However, if I were to implement the service as a singleton via java enum's, this makes wiring it up via Spring a bit more problematic.
So, how do other people typically deal with reference data? Query-at-will but with caching under the covers? Or a separate in-memory service?
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我通常使用 Spring 将 DAO 实现注入到我的服务层中，正如您提到的，除了基于 SQL 的实现之外，通常还有一个测试实现（
XMLDao、FlatFileDao）。 对于小型数据集，我通常编写自己的缓存并将从基础表加载的所有数据存储在内存中。综上所述，我的优势在于可以使用相当小的数据集。 如果我正在处理更大的数据集，我可能会考虑现成的缓存解决方案，可能分布在多个 JVM 上（例如 Terracotta ）。
正如我在上一个线程中提到的，我还公开了一个刷新（）方法。 如果数据更新不需要及时传播，我只需通过 MBean 手动调用即可。 在我希望自动执行此操作的情况下，我使用 Tibrv 监听数据库的更新并刷新缓存的数据（使用 MS-SQL 触发器生成 Tibrv 消息）。
我不太明白您提到使用 Java 枚举来实现服务 - 这将如何工作？
I typically inject a DAO implementation into my service layer using Spring and, as you mention often have a test implementation (
XMLDao,FlatFileDao) in addition to my SQL-based implementation. For small datasets I usually write my own cache and store all data loaded from the underlying table(s) in memory.Saying all that, I have the advantage of working with reasonably small datasets. If I were dealing with a larger dataset I may consider off-the-shelf caching solutions, possibly distributed across multiple JVMs (like Terracotta).
As I mentioned in the previous thread I also expose a refresh() method. In cases where updates to the data do not need to propagate in a timely manner I simply call this manually via an MBean. In situations where I wish to automate this I've used Tibrv to listen to updates from the database and refresh the cached data (using an MS-SQL trigger to generate a Tibrv message).
I don't quite understand your reference to using Java enums to implement the service - How would this work?