JDK源码分析——AbstractOwnableSynchronizer类

发表于 | 分类于

抽象类AbstractOwnableSynchronizer该类是主要定义让线程以独占方式拥有同步器，此类为创建锁和相关同步器提供了基础，类本身不管理或使用此信息很简单的两个方法setExclusiveOwnerThread(Thread t)设置当前拥有独占访问的线程和getExclusiveOwnerThread()返回由setExclusiveOwnerThread最后设置的线程；如果从未设置，则返回null。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
/**
 * A synchronizer that may be exclusively owned by a thread.  This
 * class provides a basis for creating locks and related synchronizers
 * that may entail a notion of ownership.  The
 * {@code AbstractOwnableSynchronizer} class itself does not manage or
 * use this information. However, subclasses and tools may use
 * appropriately maintained values to help control and monitor access
 * and provide diagnostics.
 *
 * @since 1.6
 * @author Doug Lea
 */
// 一个线程，可能独占一个同步锁。AbstractOwnableSynchronizer用于表示锁与持有者之间的关系； 
// AbstractOwnableSynchronizer不管理这种关系；主要是其子类，用于控制或监视锁的状态，提供帮助。 
public abstract class AbstractOwnableSynchronizer
    implements java.io.Serializable {

    /** Use serial ID even though all fields transient. */
    private static final long serialVersionUID = 3737899427754241961L;

    /**
     * Empty constructor for use by subclasses.
     */
    protected AbstractOwnableSynchronizer() { }

    /**
     * The current owner of exclusive mode synchronization.
     */
    // 独占模式，锁的持有者
    private transient Thread exclusiveOwnerThread;

    /**
     * Sets the thread that currently owns exclusive access.
     * A {@code null} argument indicates that no thread owns access.
     * This method does not otherwise impose any synchronization or
     * {@code volatile} field accesses.
     * @param thread the owner thread
     */
    // 设置锁持有者
    protected final void setExclusiveOwnerThread(Thread thread) {
        exclusiveOwnerThread = thread;
    }

    /**
     * Returns the thread last set by {@code setExclusiveOwnerThread},
     * or {@code null} if never set.  This method does not otherwise
     * impose any synchronization or {@code volatile} field accesses.
     * @return the owner thread
     */
    // 获取锁的持有线程
    protected final Thread getExclusiveOwnerThread() {
        return exclusiveOwnerThread;
    }
}