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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/lang/InheritableThreadLocal.java
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+/* InheritableThreadLocal -- a ThreadLocal which inherits values across threads
+ Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006 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., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 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;
+
+/**
+ * A ThreadLocal whose value is inherited by child Threads. The value of the
+ * InheritableThreadLocal associated with the (parent) Thread is copied to
+ * the new (child) Thread at the moment of creation.
+ *
+ * <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. The utility of this class
+ * is in transferring items like User ID or Transaction ID across threads
+ * automatically.
+ *
+ * @author Mark Wielaard (mark@klomp.org)
+ * @author Eric Blake (ebb9@email.byu.edu)
+ * @author Tom Tromey (tromey@redhat.com)
+ * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
+ * @see ThreadLocal
+ * @since 1.2
+ * @status updated to 1.4
+ */
+public class InheritableThreadLocal<T> extends ThreadLocal<T>
+{
+
+ /**
+ * Creates a new InheritableThreadLocal that has no values associated
+ * with it yet.
+ */
+ public InheritableThreadLocal()
+ {
+ }
+
+ /**
+ * Determines the value associated with a newly created child Thread as a
+ * function of the value associated with the currently executing (parent)
+ * Thread. The default implementation just returns the parentValue.
+ *
+ * @param parentValue the value of this object in the parent thread at
+ * the moment of creation of the child
+ * @return the initial value for the child thread
+ */
+ protected T childValue(T parentValue)
+ {
+ return parentValue;
+ }
+
+ /**
+ * 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 constructor Thread.
+ *
+ * @param childThread the newly created thread, to inherit from this thread
+ * @see Thread#Thread(ThreadGroup, Runnable, String)
+ */
+ static void newChildThread(Thread childThread)
+ {
+ // The currentThread is the parent of the new thread.
+ Thread parentThread = Thread.currentThread();
+ childThread.locals.inherit(parentThread.locals);
+ }
+}