org.argeo.slc.repo/src/org/eclipse/aether/SessionData.java

   1 /*******************************************************************************
   2  * Copyright (c) 2010, 2014 Sonatype, Inc.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Eclipse Public License v1.0
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/epl-v10.html
   7  *
   8  * Contributors:
   9  *    Sonatype, Inc. - initial API and implementation
  10  *******************************************************************************/
  11 package org.eclipse.aether;
  12
  13 /**
  14  * A container for data that is specific to a repository system session. Both components within the repository system
  15  * and clients of the system may use this storage to associate arbitrary data with a session.
  16  * <p>
  17  * Unlike a cache, this session data is not subject to purging. For this same reason, session data should also not be
  18  * abused as a cache (i.e. for storing values that can be re-calculated) to avoid memory exhaustion.
  19  * <p>
  20  * <strong>Note:</strong> Actual implementations must be thread-safe.
  21  *
  22  * @see RepositorySystemSession#getData()
  23  * @noimplement This interface is not intended to be implemented by clients.
  24  * @noextend This interface is not intended to be extended by clients.
  25  */
  26 public interface SessionData
  27 {
  28
  29     /**
  30      * Associates the specified session data with the given key.
  31      *
  32      * @param key The key under which to store the session data, must not be {@code null}.
  33      * @param value The data to associate with the key, may be {@code null} to remove the mapping.
  34      */
  35     void set( Object key, Object value );
  36
  37     /**
  38      * Associates the specified session data with the given key if the key is currently mapped to the given value. This
  39      * method provides an atomic compare-and-update of some key's value.
  40      *
  41      * @param key The key under which to store the session data, must not be {@code null}.
  42      * @param oldValue The expected data currently associated with the key, may be {@code null}.
  43      * @param newValue The data to associate with the key, may be {@code null} to remove the mapping.
  44      * @return {@code true} if the key mapping was successfully updated from the old value to the new value,
  45      *         {@code false} if the current key mapping didn't match the expected value and was not updated.
  46      */
  47     boolean set( Object key, Object oldValue, Object newValue );
  48
  49     /**
  50      * Gets the session data associated with the specified key.
  51      *
  52      * @param key The key for which to retrieve the session data, must not be {@code null}.
  53      * @return The session data associated with the key or {@code null} if none.
  54      */
  55     Object get( Object key );
  56
  57 }