The AbstractMetadataExtractor class reads the <classname>_metadata_extract.properties file, so that it knows how to map metadata returned from the sub class extractMetadata method onto content model properties. The following is an example for an email (file extension .eml):
# # RFC822MetadataExtractor - default mapping # # Namespaces namespace.prefix.imap=http://www.alfresco.org/model/imap/1.0 namespace.prefix.cm=http://www.alfresco.org/model/content/1.0 # Mappings messageFrom=imap:messageFrom, cm:originator messageTo=imap:messageTo, cm:addressee messageCc=imap:messageCc, cm:addressees messageSubject=imap:messageSubject, cm:title, cm:description, cm:subjectline messageSent=imap:dateSent, cm:sentdate messageReceived=imap:dateReceived Thread-Index=imap:threadIndex Message-ID=imap:messageId
As can be seen, the email’s metadata for messageFrom (if available) will be used to set two properties in the content repository (if they exist): imap:messageFrom, cm:originator. The property names use namespace prefixes specified above.