Event Module

Owned by Ben Wolfe
Last updated: Dec 31, 2020 by Artur Fijał
2 min read

What this module does

This module creates easy handle points for other modules to hook onto. When an event occurs in openmrs it will notify all registered/subscribed listeners.

Downloads

View Source: https://github.com/openmrs/openmrs-module-event
Checkout Source: https://github.com/openmrs/openmrs-module-event
Download: https://addons.openmrs.org/#/show/org.openmrs.module.event

Technical Documentation

Possible Actions

An enum on Event.Action contains the possible actions of CREATED, UPDATED, RETIRED, UNRETIRED, VOIDED, UNVOIDED, PURGED

Registering module domain objects for which to fire events

The module's domain objects must be subclasses of OpenmrsObject.
If you wish for retired/unretired or voided/unvoided events to be fired, they should implement Retireable or Voidable respectively.

To subscribe to an event

In your module activator or anywhere else in your module code:

Event.subscribe(Class, String, EventListener); // The String argument can be any of the values in the Event.Action Enum or Event.setSubscription(SubscribableEventListener); // spring callable, see below

or in your Spring moduleApplicationContext:

<bean class="org.openmrs.eventbus.Event"> <property name="subscription"><bean class="org.your.module.package.SubscribableEventListenerImpl"></bean></property> </bean>

A SubscribableEventListener specifies the list of Classes and list of Actions that it supports.

Getting notified of an event.

The module uses apache's ActiveMQ messaging server, your EventListener class should extend EventListener and its onMessage(Message message) will be called

Unsubscribing from an event

Event.unsubscribe(Class, Action, EventListener); or Event.unsetSubscription(SubscribableEventListener); // just because its cute

Using external ActiveMQ instance

By default, event module uses embedded ActiveMQ instance.
If you would like to use standalone ActiveMQ instance, simply set activeMQ.externalUrl Global property with a value of your desired ActiveMQ instance and restart module.
Example ip address: 172.17.0.1:61616

Example Client code

  • The Atom Feed Module takes advantage of this module.

  • The below class should be registered to the Event class with Event.subscribe(____, new CountEventListener());

Release Notes

2.2.1

  • Fixes the issue of OpenMRS hanging on startup due to incorrect activemq-data location (EVNT-31)

2.2 (broken for bean subscription, please use 2.2.1)

2.0.1

  • Changed module so that it works via Hibernate Interceptors instead of AOP (EVNT-22)

1.2

  • Handle saving of subclasses (EVNT-23)

  • Added person to list of supported classes (EVNT-24)

1.1

  • Handle events on Orders (EVNT-21)

1.0

  • To be written after release