src/com/google/enterprise/adaptor/sharepoint/AsyncCacheLoader.java

// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.enterprise.adaptor.sharepoint;

import com.google.common.cache.CacheLoader;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.SettableFuture;

import java.util.concurrent.Executor;

/**
 * An abstract CacheLoader whose reload() is asynchronous (unlike the default).
 */
abstract class AsyncCacheLoader<K, V> extends CacheLoader<K, V> {
  protected abstract Executor executor();

  @Override
  public ListenableFuture<V> reload(final K key, V oldValue) {
    final SettableFuture<V> future = SettableFuture.create();
    executor().execute(new Runnable() {
      @Override
      public void run() {
        try {
          future.set(load(key));
        } catch (Throwable t) {
          future.setException(t);
        }
      }
    });
    return future;
  }
}