A common request is to integrate the Alfresco Share calendar with an external calendaring system such as Outlook, Google Calendar, or Zimbra. Without an integration, people end up doing double-entry. You’ve already got a calendar that works pretty well. Why make people re-enter events in Alfresco Share?

Most people use Alfresco Share for team collaboration. The calendar doesn’t need to show everything on everyone’s calendar–that job is better left to the existing calendar server. What makes more sense is to show a few team-related events or milestones on the team’s Alfresco Share site calendar or maybe in a dashlet on the site’s dashboard.

When thinking about the problem, I realized that the calendar in Share is just another interested party in an event. Just as some calendaring systems allow you to “invite” a conference room to a meeting which effectively reserves that room for the meeting, you ought to be able to “invite” a Share site and have the Share site add that event to its calendar and update it when the event changes.

Treating the Share site as just another invitee is a non-invasive way to integrate with the calendaring system and it has the added benefit that only events in which the Share site was specifically invited will show up on the Share site calendar.

As luck would have it, the pieces to make this work already exist and they don’t require any changes to the source calendaring system. Check it out:

• When you invite someone to a calendar event the calendaring system sends an iCalendar (.ICS) file as an email attachment to the invitee. The invitee’s email or calendaring client recognizes that attachment and updates the calendar accordingly.
• There’s a Java library called iCal4j that knows how to parse iCalendar files. Yea for standards!
• Alfresco supports receiving inbound email and you can easily bind custom logic to the creation of nodes. Alfresco creates one document for the email body and one for the ICS file attachment.
• Events that show up on the Alfresco Share calendar are just content-less objects–they are instances of ia:calendarEvent.

Put those pieces together and a simple one-way calendar integration is born. The integration watches for incoming email with ICS attachments, parses the attachment, then creates, updates, or deletes the corresponding Alfresco Share site calendar object.

With this in place, all you have to do to add an event to the Alfresco Share site calendar is invite the Share site to the event from your favorite calendaring system.

But what’s the invitee name of a Share site? Great question! In Alfresco, there’s an aspect called email alias. You can add it to any folder and give it an arbitrary value. Then, when sending email to Alfresco you can specify the alias.

My integration includes code that makes sure all Share sites have a folder that can be used to store inbound email and it gives that folder an alias equal to the Share site’s short name (which is used as part of the Share URL). So if your Share site is called “test-site-1” and you normally send email to Alfresco via alfresco.someco.com, your Share site’s email address becomes test-site-1@alfresco.someco.com.

What about updates? Calendar systems have a universal identifier for every event. When calendar entries are updated or deleted, the calendaring system sends an iCalendar file just as it does for new events. Included in that file is the event’s unique ID and a flag that indicates whether the event is being created or deleted. When the integration creates the event in the Alfresco Share calendar, it stores the unique ID in the Alfresco object’s metadata which it can use later to match up subsequent update and delete requests.

How about a demo?

This video shows the integration in action. Be sure to make it full screen and select “HD”.

(If you can’t see the video, watch it on YouTube here).

What’s left to do?

This is a simple, one-way integration. It does not tell the corporate calendaring system which sites are available and it does not do a free-busy lookup. It also does not acknowledge the invitation back to the source calendaring system. I don’t consider these to be critical gaps but those features might make the integration tighter.

As a side-note, the automatic creation of an email alias for a Share site and a corresponding folder to hold inbound email (which users could then configure rules for) might be useful as a separate add-on even if you don’t need calendar integration. If you agree, let me know. Maybe the integration ought to be split into two separate AMPs.

Pull requests welcome

As usual, I welcome your participation on this project. If you find problems, fix problems, or want to make improvements, use the github project to create issues and pull requests.