1 ThreadLocal.class
2 /**
3 * Sets the current thread's copy of this thread-local variable
4 * to the specified value. Most subclasses will have no need to
5 * override this method, relying solely on the {@link #initialValue}
6 * method to set the values of thread-locals.
7 *
8 * @param value the value to be stored in the current thread's copy of
9 * this thread-local.
10 */
11 public void set(T value) {
12 Thread t = Thread.currentThread();
13 //根据线程局部变量ThreadLocal实例来获取与之对应的ThreadLocalMap实例
14 ThreadLocalMap map = getMap(t);
15 if (map != null)
16 //如果ThreadLocalMap 不为null，那么就以ThreadLocal为key,以value为值，进行绑定
17 map.set(this, value);
18 else
19 /**
20 *如果根据当前的线程局部变量没有获取到与之绑定的ThreadLocal.ThreadLocalMap实例，
21 *那么就创建一个 ThreadLocal.ThreadLocalMap实例
22 *且以当前的线程为 key，传入的绑定值 为 value
23 *
24 */
25 createMap(t, value);
26 }
27
28
29
30 ThreadLocal.class
31
32 // 在ThreadLocal.java的 224行
33 /**
34 * Create the map associated with a ThreadLocal. Overridden in
35 * InheritableThreadLocal.
36 *
37 * @param t the current thread
38 * @param firstValue value for the initial entry of the map
39 * @param map the map to store.
40 */
41 void createMap(Thread t, T firstValue) {
42 //这一段代码就把当前线程与 ThreadLocal(下面一行代码里的this就是 ThreadLocal)以及要绑定的值 关联了起来
43 t.threadLocals = new ThreadLocalMap(this, firstValue);
44 }
45
46
47 Thread.class的180行
48
49 /* ThreadLocal values pertaining to this thread. This map is maintained
50 * by the ThreadLocal class. */
51 ThreadLocal.ThreadLocalMap threadLocals = null;
52 /*
53 *通过 Thread类的180行的这行代码我们可以知道，每个线程实例都有一个
54 * 类型为 ThreadLocal.ThreadLocalMap 的threadLocals属性，
55 * 这个属性的一个很重要的作用就是 接收 在ThreadLocal.java的224行的
56 * 方法 createMap(Thread t,T firstValue)里 new的TheadLocalMap变量
57 */
58 ThrealLocal.ThreadLocalMap.class
59
60 /**
61 * Construct a new map initially containing (firstKey, firstValue).
62 * ThreadLocalMaps are constructed lazily, so we only create
63 * one when we have at least one entry to put in it.
64 * 这里是 ThrealLocal.ThreadLocalMap 构造器，
65 */
66 ThreadLocalMap(ThreadLocal firstKey, Object firstValue) {
67 table = new Entry[INITIAL_CAPACITY];
68 int i = firstKey.threadLocalHashCode & (INITIAL_CAPACITY - 1);
69 table[i] = new Entry(firstKey, firstValue);
70 size = 1;
71 setThreshold(INITIAL_CAPACITY);
72 }
73
74
75
76
77
78 ThreadLocal.class
79 /**
80 * Returns the value in the current thread's copy of this
81 * thread-local variable. If the variable has no value for the
82 * current thread, it is first initialized to the value returned
83 * by an invocation of the {@link #initialValue} method.
84 *
85 * @return the current thread's value of this thread-local
86 */
87 public T get() {
88 Thread t = Thread.currentThread();
89 ThreadLocalMap map = getMap(t);
90 if (map != null) {
91 ThreadLocalMap.Entry e = map.getEntry(this);
92 if (e != null)
93 return (T)e.value;
94 }
95 return setInitialValue();
96 }
