diff -r fd16c54261b3 -r 90ce3da70b43 jdk/src/share/classes/java/lang/InheritableThreadLocal.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/jdk/src/share/classes/java/lang/InheritableThreadLocal.java Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,84 @@ +/* + * Copyright 1998-2004 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Sun designates this + * particular file as subject to the "Classpath" exception as provided + * by Sun in the LICENSE file that accompanied this code. + * + * This code 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 + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + */ + +package java.lang; +import java.lang.ref.*; + +/** + * This class extends ThreadLocal to provide inheritance of values + * from parent thread to child thread: when a child thread is created, the + * child receives initial values for all inheritable thread-local variables + * for which the parent has values. Normally the child's values will be + * identical to the parent's; however, the child's value can be made an + * arbitrary function of the parent's by overriding the childValue + * method in this class. + * + *

Inheritable thread-local variables are used in preference to + * ordinary thread-local variables when the per-thread-attribute being + * maintained in the variable (e.g., User ID, Transaction ID) must be + * automatically transmitted to any child threads that are created. + * + * @author Josh Bloch and Doug Lea + * @see ThreadLocal + * @since 1.2 + */ + +public class InheritableThreadLocal extends ThreadLocal { + /** + * Computes the child's initial value for this inheritable thread-local + * variable as a function of the parent's value at the time the child + * thread is created. This method is called from within the parent + * thread before the child is started. + *

+ * This method merely returns its input argument, and should be overridden + * if a different behavior is desired. + * + * @param parentValue the parent thread's value + * @return the child thread's initial value + */ + protected T childValue(T parentValue) { + return parentValue; + } + + /** + * Get the map associated with a ThreadLocal. + * + * @param t the current thread + */ + ThreadLocalMap getMap(Thread t) { + return t.inheritableThreadLocals; + } + + /** + * Create the map associated with a ThreadLocal. + * + * @param t the current thread + * @param firstValue value for the initial entry of the table. + * @param map the map to store. + */ + void createMap(Thread t, T firstValue) { + t.inheritableThreadLocals = new ThreadLocalMap(this, firstValue); + } +}