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因为我有一个批量操作来获取数据，所以我不想使用 refresh() 来更新单个项目，我想利用批量调用来定期更新缓存。

我想到了一些方法，因为我一直在调用 get() 来缓存，我想知道哪种方法是最佳的。

方法 1 定期调用 getAll()，它调用 loadAll()

LoadingCache<String, String> cache = CacheBuilder.newBuilder()
            .ticker(ticker)
            .refreshAfterWrite(5,  TimeUnit.Minut)
            .expireAfterAccess(30, TimeUnit.MINUTES)
            .build(cacheLoader);

private static final class CacheLoader extends CacheLoader<String, String> {
    @Override
    public String load(final String key) {
           return db.getItem(key);
    }
    @Override
    public ListenableFuture<String> reload(String key) {
      ListenableFutureTask<String> task = ListenableFutureTask.create(new Callable<String>() {
               public String call() {
                 return db.getItem(key);
               }
             });
             executor.execute(task);
             return task;
    } 
    @Override
    public String loadAll(final List<String> key) {
           return db.bulkGetItems(keyList);
    }

}

private class RefresherRunnable implements Runnable {
    private volatile boolean stopped = false;
    @Override
    public void run() {
        while (!stopped) {
            try {
               List<String> keys = getKeys();
                cache.getAll(keys);
            } catch (Exception e) {
              //log

            }

            final long nextSleepInterval = 1000 * 60;
            try {
                Thread.sleep(nextSleepInterval);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }
}

方法二

只需使用Cache.asMap().putAll

private class RefresherRunnable implements Runnable {
    private volatile boolean stopped = false;
    @Override
    public void run() {
        while (!stopped) {
            try {
               List<String> keys = getKeys();
               Map<String, String> keyValueMap = db.bulkGetItems(keys);
               cache.asMap().putAll(keyValueMap);
            } catch (Exception e) {
              //log

            }

            final long nextSleepInterval = 1000 * 60;
            try {
                Thread.sleep(nextSleepInterval);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    }
}

我从https://github.com/google/guava/wiki/CachesExplained#inserted-directly读到过， 听起来 getAll 比 asMap.put() 好，所以我猜是首选方法 1？

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