ThreadLocal

发表于 | 更新于 | 分类于 | | 阅读次数：

ThreadLocal 类结构图

image

get

1
2
3
4
5
6
7
8
9
10
11
12
13
public T get() {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null) {
                @SuppressWarnings("unchecked")
                T result = (T)e.value;
                return result;
            }
        }
        return setInitialValue();
    }

set

1
2
3
4
5
6
7
8
public void set(T value) {
      Thread t = Thread.currentThread();
      ThreadLocalMap map = getMap(t);
      if (map != null)
          map.set(this, value);
      else
          createMap(t, value);
  }

remove

1
2
3
4
5
public void remove() {
    ThreadLocalMap m = getMap(Thread.currentThread());
    if (m != null)
        m.remove(this);
}

setInitialValue

1
2
3
4
5
6
7
8
9
10
private T setInitialValue() {
       T value = initialValue();
       Thread t = Thread.currentThread();
       ThreadLocalMap map = getMap(t);
       if (map != null)
           map.set(this, value);
       else
           createMap(t, value);
       return value;
   }

initialValue

1
2
3
protected T initialValue() {
    return null;
}

getMap

1
2
3
ThreadLocalMap getMap(Thread t) {
    return t.threadLocals;
}

createMap

1
2
3
void createMap(Thread t, T firstValue) {
      t.threadLocals = new ThreadLocalMap(this, firstValue);
  }