public void setExport(String mdcKey) {
        requireNonNull(mdcKey, "mdcKey");
        checkArgument(!mdcKey.isEmpty(), "mdcKey must not be empty");
        configureExporter(builder -> builder.keyPattern(mdcKey));
    }
Adds the property represented by the specified MDC key to the export list.
Note: this method is meant to be used for XML configuration.
Use {@code add*()} methods instead.
logback/logback12/src/main/java/com/linecorp/armeria/common/logback/RequestContextExportingAppender.java