public <T extends PropertyContainer> T indexPutIfAbsent(
Index<T> index, T entity, String key, Object value) {
T existing = index.get(key, value).getSingle();
if (existing != null) {
return existing;
}
// Grab lock
IndexLock lock = new IndexLock(index.getName(), key);
TransactionState state = getTransactionState();
LockElement writeLock = state.acquireWriteLock(lock);
// Check again -- now holding the lock
existing = index.get(key, value).getSingle();
if (existing != null) {
// Someone else created this entry, release the lock as we won't be needing it
writeLock.release();
return existing;
}
// Add
index.add(entity, key, value);
return null;
}
