Subscribe to EventQueues
Subscribe by @Subscribe
- Available for ZK:
A method (as if in an EventListener) in SelectorComposer can subscribe to an EventQueue by @Subscribe. For example,
// in sender composer
public void publish() {
EventQueue<Event> eq = EventQueues.lookup("queue1", EventQueues.DESKTOP, true);
eq.publish(new Event("onMyEvent", component, data));
}
// in receiver composer
@Subscribe("queue1")
public void receive(Event event) {
// this method will be called when EventQueue "queue1" of Desktop scope is published
Object data = event.getData();
Component target = event.getTarget();
}
- Notice the queue name should match.
- ZK executes both methods in a servlet thread, so if they execute a time-consuming operation, they will block users.
In the example above, when you publish an event in the EventQueue, the subscribed method will be called. This is a useful mechanism to communicate among composers. See also EventQueue.
EventQueue Scope
You can subscribe to EventQueue of different scopes.
@Subscribe(value = "queue2", scope = EventQueues.SESSION)
public void method2(Event event) {
// this method will be called when EventQueue "queue2" of Session scope is published
}
public void publish() {
EventQueue<Event> eq = EventQueues.lookup("queue2", EventQueues.SESSION, true);
eq.publish(new Event("onMyEvent", component, data));
}
Available scopes are: Desktop, Group, Session, Application. Note that Group scope requires ZK EE. See also EventQueues.
Event Name
Since 7.0.3 You can also listen to a specified event name.
@Subscribe(value = "queue2", eventName = "event1")
public void method2(Event event) {
// this method will be called when EventQueue "queue2" of Session scope is published
}
public void publish() {
EventQueue<Event> eq = EventQueues.lookup("queue2", EventQueues.DESKTOP, true);
eq.publish(new Event("event1", component, data));
}
Subscriber Method Parameter
The method which subscribes to the EventQueue takes either no parameter or one parameter of a type Event.
@Subscribe("queue3")
public void method3() { // the event parameter can be omitted
// ...
}
Since 7.0.3 ZK automatically maps event data into the method parameters in order.
@Subscribe("queue3")
public void method3(int i, String s) {
// i will be 100, s will be "eventData"
// ...
}
public void publish() {
EventQueue<Event> eq = EventQueues.lookup("queue3", EventQueues.DESKTOP, true);
eq.publish(new Event("event1", component, new Object[]{100, "eventData"}));
}
If you put the event at the first one, it also works well.
@Subscribe("queue3")
public void method3(Event event, int i, String s) {
// ...
}
To recap, we now have four ways to use a parameter:
- method()
- method(Event event)
- method(Event event, int d1, String d2, ....)
- method(int d1, String d2, ...)
Auto-Unsubscribed
@Subscribe
will unsubscribe the subscribed event-queue automatically when the applied component (or its ancestor) of a composer is detached.
Version History
Version | Date | Content |
---|---|---|
6.0.1 | April 2012 | @Subscribe was introduced. |
7.0.3 | June 2014 | ZK-2076 Enhance Subscribe annotation to map java method by the event name and the parameter type in order |