/**
* get data synchronous and preload new data asynchronous according to keyList
*
* @param key
* @param keyList key list, if is null, not preload, else preload forward by {@link
* #preloadDataForward(Object, List, int)}, preload backward by {@link
* #preloadDataBackward(Object, List, int)}
* @return element if this cache contains the specified key, else get data realtime and wait for
* it
* @see PreloadDataCache#get(Object)
*/
public CacheObject<V> get(K key, List<K> keyList) {
if (key == null) {
return null;
}
// if list is not null, preload data
if (!ListUtils.isEmpty(keyList)) {
preloadDataForward(key, keyList, forwardCacheNumber);
preloadDataBackward(key, keyList, backwardCacheNumber);
}
return get(key);
}
/**
* preload data backward
*
* <ul>
* <strong>Preload rule below:</strong><br>
* If key is null or list is empty, not preload, else circle keyList back to front.<br>
* If entry in the list equals to key, begin preload until to the front of list or preload count
* has reached cacheCount, like this:
* <li>if entry is already in cache or is getting data, continue last entry. else
* <li>new thread to get data and continue last entry
* </ul>
*
* @param key
* @param keyList if is null, not preload
* @param cacheCount count for preload forward
* @return count for getting data, that is cacheCount minus count of keys whose alreadey in cache
*/
protected int preloadDataBackward(K key, List<K> keyList, int cacheCount) {
int gettingDataCount = 0;
if (key != null && !ListUtils.isEmpty(keyList) && onGetDataListener != null) {
int cachedCount = 0;
boolean beginCount = false;
for (int i = keyList.size() - 1; i >= 0 && cachedCount <= cacheCount; i--) {
K k = keyList.get(i);
if (ObjectUtils.isEquals(k, key)) {
beginCount = true;
continue;
}
if (k != null && beginCount) {
cachedCount++;
if (gettingData(k) != null) {
gettingDataCount++;
}
}
}
}
return gettingDataCount;
}