| /* java.lang.InheritableThreadLocal |
| Copyright (C) 2000, 2001 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package java.lang; |
| |
| import java.util.Iterator; |
| import java.util.HashSet; |
| import java.util.Map; |
| import java.util.Set; |
| import java.util.WeakHashMap; |
| |
| /** |
| * ThreadLocal whose value is inherited by child Threads. |
| * The value of the InheritableThreadLocal associated with the (parent) Thread |
| * on the moment that it creates a new (child) Thread is set as the value that |
| * is associated with the new (child) Thread. |
| * <p> |
| * It is possible to make the value associated with the child Thread a function |
| * of the value that is associated with the parent Thread by overriding the |
| * <code>childValue()</code> method. |
| * |
| * @since 1.2 |
| * @author Mark Wielaard (mark@klomp.org) |
| */ |
| public class InheritableThreadLocal extends ThreadLocal { |
| |
| /** |
| * Maps Threads to a Set of InheritableThreadLocals |
| * (the heritage of that Thread). |
| * Uses a WeakHashMap so if the Thread is garbage collected the reference |
| * to that Set disappears. |
| * Both <code>AddToHeritage</code> access and modify it so they have to |
| * synchronize on the threadMap when they do. |
| */ |
| private static Map threadMap = new WeakHashMap(); |
| |
| /** |
| * Creates a new InheritableThreadLocal that has no values associated |
| * with it yet. |
| */ |
| public InheritableThreadLocal() { |
| super(); |
| } |
| |
| /** |
| * Determines the value associated with a newly created child Thread |
| * as a function of the value associated with the currently executing |
| * (parent) Thread. |
| * <p> |
| * The default implementation just returns the parentValue. |
| */ |
| protected Object childValue(Object parentValue) { |
| return parentValue; |
| } |
| |
| /** |
| * Adds this <code>InheritableThreadLocal</code> to the heritage of the |
| * current Thread and returns the value of the <code>ThreadLocal</code> |
| * for the Thread. The value will be either the last value that the |
| * current Thread has set, or the childValue of the last value that the |
| * parent Thread set before the current Thread was created, or the |
| * initialValue of the <code>ThreadLocal</code>. |
| * |
| * @see ThreadLocal#get() |
| */ |
| public Object get() { |
| addToHeritage(); |
| return super.get(); |
| } |
| |
| /** |
| * Adds this <code>InheritableThreadLocal</code> to the heritage of the |
| * current Thread and sets the value of the <code>ThreadLocal</code> |
| * for the Thread. |
| * |
| * @see ThreadLocal#set(Object) |
| */ |
| public void set(Object value) { |
| addToHeritage(); |
| super.set(value); |
| } |
| |
| /** |
| * Adds this <code>InheritableThreadLocal</code> to the heritage |
| * of the current Thread. |
| */ |
| private void addToHeritage() { |
| Thread currentThread = Thread.currentThread(); |
| Set heritage; |
| synchronized(threadMap) { |
| heritage = (Set)threadMap.get(currentThread); |
| } |
| // Note that we don't have to synchronize on the heritage Set |
| // since only this Thread (or the parent Thread when creating |
| // the heritage) ever modifies it. |
| if (heritage == null) { |
| heritage = new HashSet(); |
| synchronized(threadMap) { |
| threadMap.put(currentThread, heritage); |
| } |
| } |
| if (!heritage.contains(this)) { |
| heritage.add(this); |
| } |
| } |
| |
| /** |
| * Generates the childValues of all <code>InheritableThreadLocal</code>s |
| * that are in the heritage of the current Thread for the newly created |
| * childThread. |
| * Should be called from the contructor of java.lang.Thread. |
| */ |
| static void newChildThread(Thread childThread) { |
| // The currentThread is the parent of the new thread |
| Thread parentThread = Thread.currentThread(); |
| |
| // Inherit all the InheritableThreadLocals of the parent thread |
| Set heritage; |
| synchronized(threadMap) { |
| heritage = (Set)threadMap.get(parentThread); |
| } |
| // Note that we don't have to synchronize on the heritage Set |
| // since only this Thread (or the parent Thread when creating |
| // the heritage) ever modifies it. |
| if (heritage != null) { |
| synchronized(threadMap) { |
| threadMap.put(childThread, new HashSet(heritage)); |
| } |
| // And constructs all the new child values |
| // (has to be done now that we are executing in the parentThread) |
| Iterator it = heritage.iterator(); |
| while (it.hasNext()) { |
| InheritableThreadLocal local = |
| (InheritableThreadLocal) it.next(); |
| // Note that the parentValue cannot be null |
| // If it was it would not be in the heritage |
| Object parentValue = local.get(parentThread).getValue(); |
| Object childValue = local.childValue(parentValue); |
| ThreadLocal.Value v = new ThreadLocal.Value(childValue); |
| local.set(childThread, v); |
| } |
| } |
| } |
| } |