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/*******************************************************************************
* Copyright (c) 2010, 2014 Sonatype, Inc.
* 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
*
* Contributors:
* Sonatype, Inc. - initial API and implementation
*******************************************************************************/
package org.eclipse.aether;
/**
* A container for data that is specific to a repository system session. Both components within the repository system
* and clients of the system may use this storage to associate arbitrary data with a session.
*
* Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be
* abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion.
*
* Note: Actual implementations must be thread-safe.
*
* @see RepositorySystemSession#getData()
* @noimplement This interface is not intended to be implemented by clients.
* @noextend This interface is not intended to be extended by clients.
*/
public interface SessionData
{
/**
* Associates the specified session data with the given key.
*
* @param key The key under which to store the session data, must not be {@code null}.
* @param value The data to associate with the key, may be {@code null} to remove the mapping.
*/
void set( Object key, Object value );
/**
* Associates the specified session data with the given key if the key is currently mapped to the given value. This
* method provides an atomic compare-and-update of some key's value.
*
* @param key The key under which to store the session data, must not be {@code null}.
* @param oldValue The expected data currently associated with the key, may be {@code null}.
* @param newValue The data to associate with the key, may be {@code null} to remove the mapping.
* @return {@code true} if the key mapping was successfully updated from the old value to the new value,
* {@code false} if the current key mapping didn't match the expected value and was not updated.
*/
boolean set( Object key, Object oldValue, Object newValue );
/**
* Gets the session data associated with the specified key.
*
* @param key The key for which to retrieve the session data, must not be {@code null}.
* @return The session data associated with the key or {@code null} if none.
*/
Object get( Object key );
}