Observation module

The Observation module allows you to listen to events in the repository and trigger a reaction. Use observation to automate tasks such as publishing newly added assets or sending an email notification when a comment is added. Custom event listeners can react to almost any event. The Observation module is based on the JCR observation feature.  

Download

Download the Observation module from Magnolia Store or Nexus repository.

Installing

Observation is a Community Edition module.

 The Observation module is not installed by default. To check whether it is installed, go to Magnolia Store > Installed modules in AdminCentral. If you don't find a version node in /modules/observation then the module is not installed. You can find listeners installed by other modules under the config node even if the Observation module is not installed.

To install the module, please see the general module installation instructions.

Uninstalling

See the general module uninstalling instructions and advice.

Event listeners

An event listener registers an interest in a particular type of event. The job of the listener is to detect the event and possibly react to it.

Example: You want to send an email notification when a new page is added. Configure an event listener that listens to the NODE_ADDED event. This event occurs when a new node is added. Limit the listener to the mgnl:page node type so you only get notified about pages, not other types of nodes. Finally, define the mail command as the desired reaction.

Magnolia provides two types of event listeners: listeners that react to the event on their own and listeners that delegate the reaction to a command. Both listeners are configured the same way but command event listeners have some extra properties.

Listener configuration

Here is a basic pageAddedAlert listener. It listens to the NODE_ADDED event and reacts by writing a message to the console when new content is added. This is an example of a self-contained listener that reacts to the event on its own. The reaction is hard-coded in the  PageListener class.

Here's what the output written to the console looks like:

EventListener Test: Text Message
EventListener Test: Text Message2

Listener properties:

• <listener name>
  
  • listener : Identifies the configuration as an event listener.
    
    • class : Fully-qualified listener class name.
    • nodeType : Optional. Restricts observation to events that occur in the specified node type, for example mgnl:page for pages. Use together with a listener class that observes node type. By default all node types are monitored.
  • active : Enables and disables the listener. Default is false.
  • delay : Optional. Delay in milliseconds before the reaction is triggered.
  • description : Optional. Listener description.
  • eventTypes : Optional. The type of JCR event monitored. Possible types are  NODE_ADDED, NODE_MOVED, NODE_REMOVED, PROPERTY_ADDED, PROPERTY_CHANGED, PROPERTY_REMOVED and PERSIST. Separate multiple types with a comma. All types are monitored by default.
  • includeSubNodes : Optional. Observes also events in subnodes. Default is false. For example, by default only changes to the page itself would be observed. If you also want to observe changes to components under the page node, set includeSubNodes to true.
  • maxDelay : Optional. Maximum delay milliseconds before the reaction is triggered.
  • path : Mandatory. Path to the node that is observed.

  • repository : Mandatory. Workspace in which the observed node resides.

Listener classes

Magnolia provides the following listener classes:

Command event listeners

A command event listener delegates the reaction to a command. You can reuse any of Magnolia's existing commands or write your own.

Here's an example sendMailOnPageChanges listener. It observes changes to pages and delegates the reaction to MailCommand which sends a notification. This example assumes the pageChangeNotification mail template has been configured in the Mail module.

Properties specific to command listeners:

• <listener name>
  
  • command :
    
    • class: Fully-qualified name of the command class the reaction is delegated to.
    • params: Optional. Parameters passed to the command. For example the mailTemplate used to compose the mail body, required by the MailCommand.
      

      • repository : Workspace passed to the command. Some commands require this so you need to define it in two places: here as a parameter and under the listener configuration.

    • <other>: Any other configuration supported by the command. For example nodeType in the case of RestrictToNodeTypeEventListener.

  • includes: Optional. Included list of node types that the SpecifiedNodeTypeOnlyEventListener observes.
    
    • <node type name 1>: Node type to observe.
    • <node type name 2>: Node type to observe.
    • <node type name 3>: Node type to observe.
  • excludes: Optional. Excluded list of node types that the SpecifiedNodeTypeOnlyEventListener ignores.
    
    • <node type name 1>: Node type to ignore.
    • <node type name 2>: Node type to ignore.

    • <node type name 3>: Node type to ignore.
      

  • class: Fully-qualified name of the command listener class.

Examples

Magnolia provides the following example listeners:

• sendMailOnPageChanges: Sends an email message when a page is created, updated or deleted. 
• sendMailOnPageComments: Installed by the Mail module to send an email when a user comments on a page.
• activateAddedPages: Automatically activates new pages
• versionResourcesOnChange: Automatically versions STK resources.
• versionTemplatesOnChange: Installed by the In-place Templating module to automatically version STK templates.
• generateCategories: Installed by Categorization module to automatically generate categories.

Activating assets automatically

The example below automatically activates any new asset added in the DMS. The listener observes the NODE_ADDED event in the dms workspace. To test the listener, upload a new asset.