why the ThreadLocal only have threadLocalHashcode in Java

Today when I debug my app into RequestContext putLoginId method, I found the class static ThreadLocal initial failed, the contextData.get() return null, the static contextData only have threadLocalHashCode.

My contextData define in RequestContext class like this:

public class RequestContext {
    public static final ThreadLocal<Map<String, Object>> contextData = new ThreadLocal<>();
}

the contextData should be initialed when load the class, so I think it will never be null. But why this happening and what should I do to fix it? Am I missing something?

Answer

the contextData should be initialed when load the class, so I think it will never be null

contextData is initialized when the class is loaded; but you don’t actually give it a (per-thread) value, at least in the code shown.

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Give your ThreadLocal an initial value with the factory method, for example:

public static final ThreadLocal<Map<String, Object>> contextData =
    ThreadLocal.withInitial(HashMap::new);