@Override
    public String get(String key) {
        Map<String, String> hashMap = readWriteThreadLocalMap.get();

        if ((hashMap != null) && (key != null)) {
            return hashMap.get(key);
        } else {
            return null;
        }
    }
Get the context identified by the <code>key</code> parameter.
<p/>
<p/>
This method has no side effects.
zlt-commons/zlt-log-spring-boot-starter/src/main/java/org/slf4j/TtlMDCAdapter.java