@Override
public synchronized void updateEntry(final String key, final HttpCacheUpdateCallback callback)
throws IOException, HttpCacheUpdateException {
int numRetries = 0;
do {
final Element oldElement = cache.get(key);
HttpCacheEntry existingEntry = null;
if (oldElement != null) {
final byte[] data = (byte[]) oldElement.getValue();
existingEntry = serializer.readFrom(new ByteArrayInputStream(data));
}
final HttpCacheEntry updatedEntry = callback.update(existingEntry);
if (existingEntry == null) {
putEntry(key, updatedEntry);
return;
} else {
// Attempt to do a CAS replace, if we fail then retry
// While this operation should work fine within this instance, multiple instances
// could trample each others' data
final ByteArrayOutputStream bos = new ByteArrayOutputStream();
serializer.writeTo(updatedEntry, bos);
final Element newElement = new Element(key, bos.toByteArray());
if (cache.replace(oldElement, newElement)) {
return;
} else {
numRetries++;
}
}
} while (numRetries <= maxUpdateRetries);
throw new HttpCacheUpdateException("Failed to update");
}
@Override
public synchronized void putEntry(final String key, final HttpCacheEntry entry)
throws IOException {
final ByteArrayOutputStream bos = new ByteArrayOutputStream();
serializer.writeTo(entry, bos);
cache.put(new Element(key, bos.toByteArray()));
}
@Override
public synchronized HttpCacheEntry getEntry(final String key) throws IOException {
final Element e = cache.get(key);
if (e == null) {
return null;
}
final byte[] data = (byte[]) e.getValue();
return serializer.readFrom(new ByteArrayInputStream(data));
}