in flume-morphline-solr-sink/src/main/java/org/apache/flume/sink/solr/morphline/UUIDInterceptor.java [42:46]
protected UUIDInterceptor(Context context) {
headerName = context.getString(HEADER_NAME, "id");
preserveExisting = context.getBoolean(PRESERVE_EXISTING_NAME, true);
prefix = context.getString(PREFIX_NAME, "");
}