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      1 /*
      2  * Copyright (C) 2011 The Guava Authors
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.common.cache;
     18 
     19 import com.google.common.collect.ImmutableList;
     20 import com.google.common.collect.ImmutableMap;
     21 import com.google.common.collect.Lists;
     22 import com.google.common.util.concurrent.Futures;
     23 import com.google.common.util.concurrent.ListenableFuture;
     24 
     25 import junit.framework.TestCase;
     26 
     27 import java.util.LinkedList;
     28 import java.util.Map;
     29 import java.util.concurrent.Executor;
     30 import java.util.concurrent.atomic.AtomicInteger;
     31 
     32 /**
     33  * Unit tests for {@link CacheLoader}.
     34  *
     35  * @author Charles Fry
     36  */
     37 public class CacheLoaderTest extends TestCase {
     38 
     39   private static class QueuingExecutor implements Executor {
     40     private LinkedList<Runnable> tasks = Lists.newLinkedList();
     41 
     42     @Override
     43     public void execute(Runnable task) {
     44       tasks.add(task);
     45     }
     46 
     47     private void runNext() {
     48       tasks.removeFirst().run();
     49     }
     50   }
     51 
     52   public void testAsyncReload() throws Exception {
     53     final AtomicInteger loadCount = new AtomicInteger();
     54     final AtomicInteger reloadCount = new AtomicInteger();
     55     final AtomicInteger loadAllCount = new AtomicInteger();
     56 
     57     CacheLoader<Object, Object> baseLoader = new CacheLoader<Object, Object>() {
     58       @Override
     59       public Object load(Object key) {
     60         loadCount.incrementAndGet();
     61         return new Object();
     62       }
     63 
     64       @Override
     65       public ListenableFuture<Object> reload(Object key, Object oldValue) {
     66         reloadCount.incrementAndGet();
     67         return Futures.immediateFuture(new Object());
     68       }
     69 
     70       @Override
     71       public Map<Object, Object> loadAll(Iterable<? extends Object> keys) {
     72         loadAllCount.incrementAndGet();
     73         return ImmutableMap.of();
     74       }
     75     };
     76 
     77     assertEquals(0, loadCount.get());
     78     assertEquals(0, reloadCount.get());
     79     assertEquals(0, loadAllCount.get());
     80 
     81     baseLoader.load(new Object());
     82     baseLoader.reload(new Object(), new Object());
     83     baseLoader.loadAll(ImmutableList.of(new Object()));
     84     assertEquals(1, loadCount.get());
     85     assertEquals(1, reloadCount.get());
     86     assertEquals(1, loadAllCount.get());
     87 
     88     QueuingExecutor executor = new QueuingExecutor();
     89     CacheLoader<Object, Object> asyncReloader =
     90         CacheLoader.asyncReloading(baseLoader, executor);
     91 
     92     asyncReloader.load(new Object());
     93     asyncReloader.reload(new Object(), new Object());
     94     asyncReloader.loadAll(ImmutableList.of(new Object()));
     95     assertEquals(2, loadCount.get());
     96     assertEquals(1, reloadCount.get());
     97     assertEquals(2, loadAllCount.get());
     98 
     99     executor.runNext();
    100     assertEquals(2, loadCount.get());
    101     assertEquals(2, reloadCount.get());
    102     assertEquals(2, loadAllCount.get());
    103   }
    104 }
    105