package com.atlassian.cache.hazelcast;
   
   import javax.annotation.Nonnull;
   
   import com.atlassian.cache.CacheLoader;
   
   import static com.google.common.base.Preconditions.checkNotNull;
   
   /**
   * Cache loader wrapper which will re-invoke original loader if cache version changes while entry loading was in
   * progress
   * <p/>
   * Cache version changed each time when removeAll or clear is called
   */
  public class CacheVersionAwareCacheLoader<K, V> implements CacheLoader<K, V>
  {
      private final CacheLoader<K, V> delegate;
      private final CacheVersion cacheVersion;
  
      CacheVersionAwareCacheLoader(CacheLoader<K, V> delegate, CacheVersion cacheVersion)
      {
          this.delegate = checkNotNull(delegate);
          this.cacheVersion = checkNotNull(cacheVersion);
      }
  
      @Nonnull
      @Override
      public V load(@Nonnull K key)
      {
          V v;
          long currentVersion;
  
          do
          {
              currentVersion = cacheVersion.get();
              v = delegate.load(key);
          }
          while (currentVersion != cacheVersion.get());
  
          return v;
      }
  }