Subscribe to EventQueues"

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  {{ZK EE}}
 
  {{ZK EE}}
  
An method (as if in an EventListener) in [https://www.zkoss.org/javadoc/latest/zk/org/zkoss/zk/ui/select/SelectorComposer.html SelectorComposer] can subscribe to an [[ZK_Developer's_Reference/Event_Handling/Event_Queues | EventQueue]] by [https://www.zkoss.org/javadoc/latest/zk/org/zkoss/zkmax/ui/select/annotation/Subscribe.html @Subscribe]. For example,
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A method (as if in an EventListener) in [https://www.zkoss.org/javadoc/latest/zk/org/zkoss/zk/ui/select/SelectorComposer.html SelectorComposer] can subscribe to an [[ZK_Developer's_Reference/Event_Handling/Event_Queues | EventQueue]] by [https://www.zkoss.org/javadoc/latest/zk/org/zkoss/zkmax/ui/select/annotation/Subscribe.html @Subscribe]. For example,
  
 
<syntaxhighlight lang="java" highlight='3'>
 
<syntaxhighlight lang="java" highlight='3'>
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=Event Name=
 
=Event Name=
{{versionSince| 7.0.3}} You can also listen to a specified event name
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{{versionSince| 7.0.3}} You can also listen to a specified event name.
 
<syntaxhighlight lang="java" highlight='1'>
 
<syntaxhighlight lang="java" highlight='1'>
 
@Subscribe(value = "queue2", eventName = "event1")
 
@Subscribe(value = "queue2", eventName = "event1")
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eq.publish(new Event("event1", component, new Object[]{100, "eventData"}));
 
eq.publish(new Event("event1", component, new Object[]{100, "eventData"}));
 
}
 
}
</source>
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</syntaxhighlight>
  
 
If you put the event at the first one, it also works well.
 
If you put the event at the first one, it also works well.
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= Auto-Unsubscribed =
 
= Auto-Unsubscribed =
<tt>@Subscribe</tt> will unsubscribe the subscribed event-queue automatically when the applied component (or its ancestor) of a composer is detached.  
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<code>@Subscribe</code> will unsubscribe the subscribed event-queue automatically when the applied component (or its ancestor) of a composer is detached.  
  
 
<!--https://tracker.zkoss.org/browse/ZK-1438-->
 
<!--https://tracker.zkoss.org/browse/ZK-1438-->
  
 
=Version History=
 
=Version History=
{{LastUpdated}}
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{| class='wikitable' | width="100%"
 
{| class='wikitable' | width="100%"
 
! Version !! Date !! Content
 
! Version !! Date !! Content

Latest revision as of 07:17, 29 January 2024


Subscribe to EventQueues


Subscribe by @Subscribe

  • Available for ZK:
  • http://www.zkoss.org/product/zkhttp://www.zkoss.org/whyzk/zkeeVersion ee.png

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



Last Update : 2024/01/29

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.