MtContextThreadLocal（一）

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AtomicReference干嘛的？
假设releaseMtContextAfterRun为true,那么上下文仅能被执行线程使用一次。
所以

@Overridepublic void run() {    Map<MtContextThreadLocal<?>, Object> copied = copiedRef.get();    if (copied == null || releaseMtContextAfterRun && !copiedRef.compareAndSet(copied, null)) {        throw new IllegalStateException("MtContext is released!");    }    //recover context may be more easy to understand.    Map<MtContextThreadLocal<?>, Object> backup = MtContextThreadLocal.backupAndSet(copied);    try {        runnable.run();    } finally {       MtContextThreadLocal.restore(backup);    }}

只有设置了releaseMtContextAfterRun为true,那么多个线程读取时才会使用CAS获取竞态资源。
if(copied==null||(releaseMtContextAfterRun &&copiedRef.compareAndSwap(copyied,null))){
}

In fact.ThreadLocal的内部类ThreadLocalMap是个WeakHashMap

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