org.gridgain.grid.GridNodeLocalMap Maven / Gradle / Ivy
/*
Copyright (C) GridGain Systems. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
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*/
package org.gridgain.grid;
import org.jetbrains.annotations.*;
import java.util.concurrent.*;
/**
* Defines interface for node-local storage.
*
* {@code GridNodeLocalMap} is similar to {@link ThreadLocal} in a way that its values are not
* distributed and kept only on local node (similar like {@link ThreadLocal} values are attached to the
* current thread only). Node-local values are used primarily by jobs executed from the remote
* nodes to keep intermediate state on the local node between executions.
*
* {@code GridNodeLocalMap} essentially is a {@link ConcurrentMap} with a few additional methods,
* so it is fairly trivial to use.
*
* You can get an instance of {@code GridNodeLocalMap} by calling {@link Grid#nodeLocalMap()} method.
*/
public interface GridNodeLocalMap extends ConcurrentMap, GridMetadataAware {
/**
* Gets the value with given key. If that value does not exist, calls given closure
* to get the default value, puts it into the map and returns it. If closure is {@code null}
* return {@code null}.
*
* @param key Key to get the value for.
* @param dflt Default value producing closure.
* @return Value for the key or the value produced by the closure if key
* does not exist in the map. Return {@code null} if key is not found and
* closure is {@code null}.
*/
public V addIfAbsent(K key, @Nullable Callable dflt);
/**
* Unlike its sibling method {@link #putIfAbsent(Object, Object)} this method returns
* current mapping from the map.
*
* @param key Key.
* @param val Value to put if one does not exist.
* @return Current mapping for a given key.
*/
public V addIfAbsent(K key, V val);
}