PROSAGA码农传奇-google guava-在Scala参数化（泛型）类型错误中使用Guava的简单缓存管理器

在Scala参数化（泛型）类型错误中使用Guava的简单缓存管理器

作者: 布偶的表弟派大星丶
发布时间: 2024-11-17 11:50:25 (1月前)
转自：

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  <P>
    由于在检索缓存时提供类型信息，因此无需尝试和维护通配符键入。将值键入AnyRef然后在结尾处将V形式转换为V要简单得多。以下编译并应该有所帮助。此外，没有必要直接调用asScalaConcurrentMap，因为它很好...隐式。
  </p>
   <pre>
    <code>
      import scala.collection.JavaConversions._
import com.google.common.collect.MapMaker
import java.util.concurrent.TimeUnit
import com.google.common.cache.CacheBuilder
import scala.collection.mutable.ConcurrentMap

trait CacheListener // not sure what this is doing yet.

trait CacheManager {

def getCache[V <: AnyRef](
            cacheName: String,
            cacheListener: Option[CacheListener] = None): ConcurrentMap[String, V]

}

class LocalCacheManager extends CacheManager {
    private val caches: ConcurrentMap[String, ConcurrentMap[String, AnyRef]] =
                new MapMaker().concurrencyLevel(4).makeMap[String, ConcurrentMap[String, AnyRef]]()
    def getCache[V <: AnyRef](cacheName: String, cacheListener: Option[CacheListener] = None) = 
      caches.getOrElseUpdate(cacheName, {
              CacheBuilder.newBuilder()
                          .concurrencyLevel(4)
                          .softValues()
                          .expireAfterAccess(30, TimeUnit.MINUTES)
                          .asInstanceOf[CacheBuilder[String, AnyRef ]]
                          .build[String, AnyRef ]()
                          .asMap()
              }).asInstanceOf[ConcurrentMap[String, V]]
}

</code>
  </pre>
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