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Document custom SimpleApplicationEventMulticaster setup 

Closes gh-29996
This commit is contained in:
Juergen Hoeller 2023-08-21 12:32:33 +02:00
parent c91708c1c0
commit 2952cb95f5
1 changed files with 29 additions and 5 deletions
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34
framework-docs/modules/ROOT/pages/core/beans/context-introduction.adoc
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@ -484,13 +484,14 @@ custom event (`BlockedListEvent` in the preceding example). This means that the
You can register as many event listeners as you wish, but note that, by default, event
listeners receive events synchronously. This means that the `publishEvent()` method
blocks until all listeners have finished processing the event. One advantage of this
synchronous and single-threaded approach is that, when a listener receives an event, it
operates inside the transaction context of the publisher if a transaction context is
available. If another strategy for event publication becomes necessary, see the javadoc
for Spring's
synchronous and single-threaded approach is that, when a listener receives an event,
it operates inside the transaction context of the publisher if a transaction context
is available. If another strategy for event publication becomes necessary, e.g.
asynchronous event processing by default, see the javadoc for Spring's
{api-spring-framework}/context/event/ApplicationEventMulticaster.html[`ApplicationEventMulticaster`] interface
and {api-spring-framework}/context/event/SimpleApplicationEventMulticaster.html[`SimpleApplicationEventMulticaster`]
implementation for configuration options.
implementation for configuration options which can be applied to a custom
"applicationEventMulticaster" bean definition.
The following example shows the bean definitions used to register and configure each of
the classes above:
@ -510,6 +511,12 @@ the classes above:
<bean id="blockedListNotifier" class="example.BlockedListNotifier">
<property name="notificationAddress" value="blockedlist@example.org"/>
</bean>
<!-- optional: a custom ApplicationEventMulticaster definition -->
<bean id="applicationEventMulticaster" class="org.springframework.context.event.SimpleApplicationEventMulticaster">
<property name="taskExecutor" ref="..."/>
<property name="errorHandler" ref="..."/>
</bean>
----
Putting it all together, when the `sendEmail()` method of the `emailService` bean is
@ -849,6 +856,23 @@ Kotlin::
TIP: This works not only for `ApplicationEvent` but any arbitrary object that you send as
an event.
Finally, as with classic `ApplicationListener` implementations, the actual multicasting
happens via a context-wide `ApplicationEventMulticaster` at runtime. By default, this is a
`SimpleApplicationEventMulticaster` with synchronous event publication in the caller thread.
This can be replaced/customized through an "applicationEventMulticaster" bean definition,
e.g. for processing all events asynchronously and/or for handling listener exceptions:
[source,java,indent=0,subs="verbatim,quotes"]
----
@Bean
ApplicationEventMulticaster applicationEventMulticaster() {
SimpleApplicationEventMulticaster multicaster = new SimpleApplicationEventMulticaster();
multicaster.setTaskExecutor(...);
multicaster.setErrorHandler(...);
return multicaster;
}
----
[[context-functionality-resources]]