浅析Java中的Caffeine缓存源码

static <K, V> BoundedLocalCache<K, V> newBoundedLocalCache(Caffeine<K, V> builder,
  @Nullable CacheLoader<? super K, V> cacheLoader, boolean async) {
  StringBuilder sb = new StringBuilder("com.github.benmanes.caffeine.cache.");
  if (builder.isStrongKeys()) {
    sb.append('S');
  } else {
    sb.append('W');
  }
  if (builder.isStrongValues()) {
    sb.append('S');
  } else {
    sb.append('I');
  }
  if (builder.removalListener != null) {
    sb.append('L');
  }
  if (builder.isRecordingStats()) {
    sb.append('S');
  }
  if (builder.evicts()) {
    sb.append('M');
    if (builder.isWeighted()) {
      sb.append('W');
    } else {
      sb.append('S');
    }
  }
  if (builder.expiresAfterAccess() || builder.expiresVariable()) {
    sb.append('A');
  }
  if (builder.expiresAfterWrite()) {
    sb.append('W');
  }
  if (builder.refreshes()) {
    sb.append('R');
  }
  try {
    Class<?> clazz = LocalCacheFactory.class.getClassLoader().loadClass(sb.toString());
    Constructor<?> ctor = clazz.getDeclaredConstructor(Caffeine.class, CacheLoader.class, boolean.class);
    @SuppressWarnings("unchecked")
    BoundedLocalCache<K, V> factory = (BoundedLocalCache<K, V>) ctor.newInstance(builder, cacheLoader, async);
    return factory;
  } catch (ReflectiveOperationException e) {
    throw new IllegalStateException(sb.toString(), e);
  }
}

/**
 * Performs the pending maintenance work and sets the state flags during processing to avoid
 * excess scheduling attempts. The read buffer, write buffer, and reference queues are
 * drained, followed by expiration, and size-based eviction.
 *
 * @param task an additional pending task to run, or {@code null} if not present
 */
@GuardedBy("evictionLock")
void maintenance(@Nullable Runnable task) {
  lazySetDrainStatus(PROCESSING_TO_IDLE);
  try {
    drainReadBuffer();
    drainWriteBuffer();
    if (task != null) {
      task.run();
    }
    drainKeyReferences();
    drainValueReferences();
    expireEntries();
    evictEntries();
    climb();
  } finally {
    if ((drainStatus() != PROCESSING_TO_IDLE) || !casDrainStatus(PROCESSING_TO_IDLE, IDLE)) {
      lazySetDrainStatus(REQUIRED);
    }
  }
}