001: /*
002: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003: *
004: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * The contents of this file are subject to the terms of either the GNU
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008: * Development and Distribution License("CDDL") (collectively, the
009: * "License"). You may not use this file except in compliance with the
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011: * http://www.netbeans.org/cddl-gplv2.html
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019: * accompanied this code. If applicable, add the following below the
020: * License Header, with the fields enclosed by brackets [] replaced by
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022: * "Portions Copyrighted [year] [name of copyright owner]"
023: *
024: * Contributor(s):
025: *
026: * The Original Software is NetBeans. The Initial Developer of the Original
027: * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
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030: * If you wish your version of this file to be governed by only the CDDL
031: * or only the GPL Version 2, indicate your decision by adding
032: * "[Contributor] elects to include this software in this distribution
033: * under the [CDDL or GPL Version 2] license." If you do not indicate a
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035: * your version of this file under either the CDDL, the GPL Version 2 or
036: * to extend the choice of license to its licensees as provided above.
037: * However, if you add GPL Version 2 code and therefore, elected the GPL
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040: */
041:
042: // XXX uses: FolderChildren, Children.MutexChildren, module system
043: // XXX lock wrapper for AbstractDocument (or Document + NbDocument.WriteLockable)
044: package threaddemo.locking;
045:
046: /**
047: * Factory for locks.
048: * @author Ales Novak (old code), Jesse Glick (rewrite - #32439)
049: */
050: public class Locks {
051:
052: private Locks() {
053: }
054:
055: /**
056: * Pseudo-lock that allows code to be synchronized with the AWT event dispatch thread.
057: * This is handy in that you can define a constant of type Lock in some API, initially
058: * set to a normal lock, and then switch everything to the event thread (or vice-versa).
059: * <p>It behaves somewhat differently from a read-write lock.
060: * <ol>
061: * <li>There is no distinction between read and write access. There is only one
062: * access mode, which is exclusive, and runs on the AWT thread, not in the
063: * caller thread.
064: * <li>There is no {@link PrivilegedLock}, so you cannot make entry or exit calls
065: * by themselves (which would make no sense).
066: * <li>You cannot specify a level. The event lock is considered to be at a higher
067: * level than any ordinary lock with a defined level. This means that from the
068: * event thread, you can enter any lock (subject to other restrictions), but
069: * while holding any <em>ordered</em> lock you may not block on the event thread
070: * (using <code>Locks.eventLock</code> methods).
071: * <li>{@link Lock#read(LockAction)}, {@link Lock#read(LockExceptionAction)},
072: * {@link Lock#write(LockAction)}, {@link Lock#write(LockExceptionAction)},
073: * {@link Lock#read(Runnable)}, and {@link Lock#write(Runnable)} when called from the
074: * event thread run synchronously. Else they all block, like
075: * {@link java.awt.EventQueue#invokeAndWait}.
076: * <li>{@link Lock#readLater(Runnable)} and {@link Lock#writeLater(Runnable)} run asynchronously, like
077: * {@link java.awt.EventQueue#invokeLater}.
078: * <li>{@link Lock#canRead} and {@link Lock#canWrite} just test whether you are in the event
079: * thread, like {@link java.awt.EventQueue#isDispatchThread}.
080: * </ol>
081: */
082: public static RWLock event() {
083: return EventLock.DEFAULT;
084: }
085:
086: /**
087: * XXX
088: */
089: public static synchronized RWLock eventHybrid() {
090: return EventHybridLock.DEFAULT;
091: }
092:
093: /**
094: * XXX
095: */
096: public static RWLock monitor(Object monitor) {
097: return new MonitorLock(monitor);
098: }
099:
100: /**
101: * Create a read/write lock.
102: * Allows control over resources that
103: * can be read by several readers at once but only written by one writer.
104: * Wrapper for {@link java.util.concurrent.locks.ReentrantReadWriteLock}.
105: */
106: public static RWLock readWrite() {
107: return new ReadWriteLockWrapper();
108: }
109:
110: /**
111: * Create a lock with a privileged key.
112: * @param privileged a key which may be used to call unbalanced entry/exit methods directly
113: * @see #readWrite()
114: */
115: public static RWLock readWrite(PrivilegedLock privileged) {
116: DuplexLock l = (DuplexLock) readWrite();
117: privileged.setParent(l);
118: return l;
119: }
120:
121: }
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