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public static void main(String[] args) {
    MDC.put(TRACE_ID, UUID.randomUUID().toString());
    logger.info("开始业务逻辑处理");
    logger.info("业务逻辑处理结束");
    MDC.remove(TRACE_ID);
    logger.info("TRACE_ID 还有吗？{}", MDC.get(TRACE_ID) != null);
}

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<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>[%t] [%X{TRACE_ID}] - %m%n</Pattern>
        </layout>
    </appender>
    <root level="debug">
        <appender-ref ref="CONSOLE"/>
    </root>
</configuration>

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[main] [d8610b0d-7db8-4926-8de0-0e14e8342018] - 开始业务逻辑处理
[main] [d8610b0d-7db8-4926-8de0-0e14e8342018] - 业务逻辑处理结束
[main] [] - TRACE_ID 还有吗？false

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public static void put(String key, String val) throws IllegalArgumentException {
    if (key == null) {
        throw new IllegalArgumentException("key parameter cannot be null");
    } else if (mdcAdapter == null) {
        throw new IllegalStateException("MDCAdapter cannot be null. See also http://www.slf4j.org/codes.html#null_MDCA");
    } else {
        mdcAdapter.put(key, val);
    }
}

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public void put(String key, String val) throws IllegalArgumentException {
    if (key == null) {
        throw new IllegalArgumentException("key cannot be null");
    }

    Map<String, String> oldMap = copyOnThreadLocal.get();
    Integer lastOp = getAndSetLastOperation(WRITE_OPERATION);

    if (wasLastOpReadOrNull(lastOp) || oldMap == null) {
        Map<String, String> newMap = duplicateAndInsertNewMap(oldMap);
        newMap.put(key, val);
    } else {
        oldMap.put(key, val);
    }
}

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final ThreadLocal<Map<String, String>> copyOnThreadLocal = new ThreadLocal<Map<String, String>>();