java - 使用 CacheBuilder 的缓存作为 Map

Question

我目前在我的应用程序中使用 ConcurrentHashMap，但我需要添加在超时期限后有效地使条目过期的功能 (expireAfterWrite)，并在删除条目时通知删除监听器。

我看到 CacheBuilder 可以提供我需要的东西，但我犹豫是否要使用它，因为我需要的是 map ，而不是缓存。我这样说( map 和缓存之间的区别)是因为 guava 缓存文档说明了这一点

Generally, the Guava caching utilities are applicable whenever:

• You are willing to spend some memory to improve speed.
• You expect that keys will sometimes get queried more than once.
• Your application would, in principle, work if every value was evicted from the cache immediately -- but you're trying to reduce duplicated work.

特别是第三个要点在我的申请中不合适。我将值存储在以后要检索的 map /缓存中(直到其到期)。此外，我的 key 通常只被查询一两次，查看缓存优势的次数不多。所以你看我的要求是 map ，而不是某种意义上的缓存。使用 CacheBuilder 作为映射来存储将在写入后过期并提供 removalListener 功能的值仍然是个好主意吗？有没有人足够了解 CacheBuilder 实现的内部结构来提供建议？

Answer 1

编辑: 当然 MapMaker 缓存功能已弃用，取而代之的是 CacheBuilder ， 我的错。不要犹豫，使用它:

Cache<Key, Graph> graphs = CacheBuilder.newBuilder()
    .concurrencyLevel(4) // read docs for more details
    .expireAfterWrite(yourExpireTime, TimeUnit.MINUTES)
    .build();

然后使用 Cache#asMap()如果您希望将其视为 ConcurrentMap。

使用 Guava 的另一个实用程序 - MapMaker .来自文档:

A builder of ConcurrentMap instances having any combination of the following features:

• keys or values automatically wrapped in weak or soft references
• least-recently-used eviction when a maximum size is exceeded
• time-based expiration of entries, measured since last access or last write
• notification of evicted (or otherwise removed) entries
• on-demand computation of values for keys not already present

(...)

The returned map is implemented as a hash table with similar performance characteristics to ConcurrentHashMap. It supports all optional operations of the ConcurrentMap interface. It does not permit null keys or values.