/* * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved. * * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 which accompanies this distribution, * and is available at http://www.eclipse.org/legal/epl-v10.html */ package org.opendaylight.controller.md.sal.common.api.data; import org.opendaylight.yangtools.concepts.Path; import com.google.common.base.Optional; import com.google.common.util.concurrent.ListenableFuture; /** * * Provides a stateful read view of the data tree. * *
* View of the data tree is a stable point-in-time snapshot of the current data tree state when * the transaction was created. It's state and underlying data tree * is not affected by other concurrently running transactions. * *
* Implementation Note: This interface is not intended to be implemented * by users of MD-SAL, but only to be consumed by them. * *
PATH
is A
.
*
* * txRead = broker.newReadOnlyTransaction(); // read Transaction is snapshot of data * txWrite = broker.newReadWriteTransactoin(); // concurrent write transaction * * txRead.read(OPERATIONAL,PATH).get(); // will return Optional containing A * txWrite = broker.put(OPERATIONAL,PATH,B); // writes B to PATH * * txRead.read(OPERATIONAL,PATH).get(); // still returns Optional containing A * * txWrite.commit().get(); // data tree is updated, PATH contains B * txRead.read(OPERATIONAL,PATH).get(); // still returns Optional containing A * * txAfterCommit = broker.newReadOnlyTransaction(); // read Transaction is snapshot of new state * txAfterCommit.read(OPERATIONAL,PATH).get(); // returns Optional containing B; ** *
* Note: example contains blocking calls on future only to illustrate * that action happened after other asynchronous action. Use of blocking call * {@link ListenableFuture#get()} is discouraged for most uses and you should * use * {@link com.google.common.util.concurrent.Futures#addCallback(ListenableFuture, com.google.common.util.concurrent.FutureCallback)} * or other functions from {@link com.google.common.util.concurrent.Futures} to * register more specific listeners. * * @param
* Type of path (subtree identifier), which represents location in
* tree
* @param , D> extends AsyncTransaction {
/**
*
* Reads data from provided logical data store located at the provided path.
*
* If the target is a subtree, then the whole subtree is read (and will be
* accessible from the returned data object).
*
* @param store
* Logical data store from which read should occur.
* @param path
* Path which uniquely identifies subtree which client want to
* read
* @return Listenable Future which contains read result
*
*
*/
ListenableFuture