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.

Installing

Maven is the easiest way to install the module. Add the following dependency to your bundle:

<dependency>
  <groupId>info.magnolia</groupId>
  <artifactId>magnolia-module-observation</artifactId>
  <version>2.0.5</version>
</dependency>

Pre-built jars are also available for download. See Installing a module for help.

magnolia-module-observation.jar

What is an event listener?

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. 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 require additional properties that the command class supports.

Listener configuration

The module includes a sample, self-contained listener,PageListener, that reacts to an event on its own. The reaction is hard-coded in the class and outputs the following message to the console when a page is added.

Output in console

EventListener Test: Text Message
EventListener Test: Text Message2

Example: Basic PageListener configuration in /modules/observation/config/listenerConfigurations.

Node name	Value
observation
config
listenerConfigurations
pageAddedAlert
listener
class	info.magnolia.module.observation.sample.PageListener
nodeType	mgnl:page
active	true
delay	31
description	Writes message to console when a page is added
eventTypes	NODE_ADDED
includeSubNodes	true
maxDelay	40
path	/
repository	website

Properties:

`listenerConfigurations`	required Listener configuration node.
`<listener name>`	required Arbitrary node name.
`listener`	required Listener node.
`class`	required Fully-qualified listener class name.
`nodeType`	optional, default is all node types Restricts observation to events on the specified node type, for example `mgnl:page` . Use together with a listener class that observes the specified node type.
`path`	required Path to the node that is observed.
`repository`	required Workspace of the observed node.
`active`	optional, default is `false` . Enables and disables the listener.
`delay`	optional Delay in milliseconds before the reaction is triggered.
`description`	optional Listener description.
`eventTypes`	optional, default is all event types Type of JCR event monitored. Options: `NODE_ADDED`, `NODE_MOVED`, `NODE_REMOVED`, `PROPERTY_ADDED`, `PROPERTY_CHANGED`, `PROPERTY_REMOVED` and `PERSIST`. Separate multiple types with a comma.
`includeSubNodes`	optional, default is `false` Observe also events in subnodes. For example, only changes to the page would be observed by default. Set to `true`, if you also want to observe changes to components under the page node.
`maxDelay`	optional Maximum delay milliseconds before the reaction is triggered.

A single listener can monitor a single nodeType or all types. To monitor two types to the exclusion of other types, two listener configurations are required. Folders and contacts, for example, require one listener to monitor folders (nodeType=mgnl:folder) and another to monitor files (nodeType=mgnl:contact). You can verify the nodeType by exporting the node to be monitored to XML and searching for the value of jcr:primaryType property in the file.

Command listener configuration

A command event listener delegates the reaction to a command. You can use an existing command or write your own.

The module installs two example command listener configurations in /modules/observation/config/listenercConfigurations/:

activateAddedPages: Uses ActivationCommand to automatically activate new pages.
sendMailOnPageChange: Uses MailCommand to send an email message when a page is created, updated or deleted. This example assumes the pageChangeNotification mail template has been configured in the Mail module.

Node name	Value
observation
config
listenerConfigurations
activateAddedPages
sendMailOnPageChanges
listener
command
class	info.magnolia.module.mail.commands.MailCommand
params
model
class	info.magnolia.module.observation.model.PageChangeNotifModel
mailTemplate	pageChangeNotification
mailTo	user@your-company.com
type	freemarker
class	info.magnolia.module.observation.commands.RestrictToNodeTypeEventListener
nodeType	mgnl:page
active	true
delay	31
description	A mail will be sent when a page is created/updated/removed
includeSubNodes	true
maxDelay	40
path	/
repository	website

Command-specific listener properties:

`listenerConfigurations`	required Listener configuration node.
`<listener name>`	required Arbitrary node name.
`listener`	required Listener node.
`command`	required Command node.
`class`	required Fully-qualified command class name the reaction is delegated to.
`params`	optional Parameters passed to the command. For example the `MailTemplate` used to compose the mail body is required by `MailCommand`.
`class`	required Fully-qualified name of the command listener class.
`nodeType`	optional, default is all node types Restricts observation to events on the specified node type.
`<listener properties>`	optional/requried Same as standard listener properties.

Listeners may rely on the Mail module to send emails. Configure SMTP setting to ensure they work.

Listener classes

The module provides the following listener classes:

`info.magnolia.module.observation.sample.PageListener`	PageListener	Writes a message to the console when a page is added.
`info.magnolia.module.observation.commands.CommandEventListener`	CommandEventListener	Executes a command when an event occurs.
`info.magnolia.module.observation.commands.RestrictToNodeTypeEventListener`	RestrictToNodeTypeEventListener	Executes a command when an event occurs in the specified node type.
`info.magnolia.module.observation.commands.RestrictToTemplateEventListener`	RestrictToTemplateEventListener	Executes a command only when an event occurs in the specified node that has a specified template type as a resource node.
`info.magnolia.module.observation.commands.RegexEventListener`	RegexEventListener	Executes a command when an event occurs in the specified node type and matches a regular expression pattern.
`info.magnolia.module.observation.commands.SpecifiedNodeTypeOnlyEventListener`	SpecifiedNodeTypeOnlyEventListener	Executes a command when an event occurs in a node that is in the "included" list of node types and not on the "excluded" list.

Example: Activating assets automatically

This example command listener configuration observes the NODE_ADDED event in the dam workspace. To test the listener, upload a new asset.

The dam workspace is defined twice. The property is always required under the listener configuration. In this case it is also required as a parameter by the ActivationCommand.

Example: Automatically activate new assets added in the Assets app.

Node name	Value
listenerConfigurations
activateAssets
listener
command
class	info.magnolia.module.activation.commands.ActivationCommand
params
repository	dam
class	info.magnolia.module.observation.commands.RestrictToNodeTypeEventListener
nodeType	mgnl:asset
active	true
description	Automatically activate new assets
eventTypes	NODE_ADDED
path	/
repository	dam

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