2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.mdsal.common.api;
10 import org.opendaylight.yangtools.concepts.Path;
14 * Marker interface for stateful read view of the data tree.
17 * View of the data tree is a stable point-in-time snapshot of the current data tree state when the
18 * transaction was created. It's state and underlying data tree is not affected by other
19 * concurrently running transactions.
22 * <b>Implementation Note:</b> This interface is not intended to be implemented by users of MD-SAL,
23 * but only to be consumed by them.
25 * <h2>Transaction isolation example</h2>
26 * Lets assume initial state of data tree for <code>PATH</code> is <code>A</code>.
29 * txRead = broker.newReadOnlyTransaction(); // read Transaction is snapshot of data
30 * txWrite = broker.newReadWriteTransactoin(); // concurrent write transaction
32 * txRead.read(OPERATIONAL, PATH).get(); // will return Optional containing A
33 * txWrite = broker.put(OPERATIONAL, PATH, B); // writes B to PATH
35 * txRead.read(OPERATIONAL, PATH).get(); // still returns Optional containing A
37 * txWrite.submit().get(); // data tree is updated, PATH contains B
38 * txRead.read(OPERATIONAL, PATH).get(); // still returns Optional containing A
40 * txAfterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state
41 * txAfterCommit.read(OPERATIONAL, PATH).get(); // returns Optional containing B;
45 * <b>Note:</b> example contains blocking calls on future only to illustrate that action happened
46 * after other asynchronous action. Use of blocking call
47 * {@link com.google.common.util.concurrent.ListenableFuture#get()} is discouraged for most uses and
49 * {@link com.google.common.util.concurrent.Futures#addCallback(com.google.common.util.concurrent.ListenableFuture, com.google.common.util.concurrent.FutureCallback)}
50 * or other functions from {@link com.google.common.util.concurrent.Futures} to register more
53 * @param <P> Type of path (subtree identifier), which represents location in tree
54 * @param <D> Type of data (payload), which represents data payload
57 public interface AsyncReadTransaction<P extends Path<P>, D> extends AsyncTransaction<P, D> {