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Improve docs for global default poller

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* Fix Kotlin deprecation warning in the test
* Replace wrong `IntervalTrigger` mentioning in the docs to the proper `PeriodicTrigger`
* Fix code snippet in the `channel-adapter.adoc`
This commit is contained in:
Artem Bilan
2021-09-20 10:31:36 -04:00
parent 0fb64f1762
commit b92d52fe74
3 changed files with 77 additions and 12 deletions
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2
spring-integration-core/src/test/kotlin/org/springframework/integration/dsl/KotlinDslTests.kt
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@@ -258,7 +258,7 @@ class KotlinDslTests {
@Bean
fun functionFlow2() =
integrationFlow<Function<*, *>> {
transform<String> { it.toLowerCase() }
transform<String> { it.lowercase() }
filter(UnexpiredMessageSelector())
route<Message<*>, Any?>({ null }) { defaultOutputToParentFlow() }
route<Message<*>> { m -> m.headers.replyChannel }

3
src/reference/asciidoc/channel-adapter.adoc
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@@ -124,6 +124,8 @@ However, if you are sure that your method can return null and you need to poll f
====
Starting with version 5.5, a `0` value for `max-messages-per-poll` has a special meaning - skip the `MessageSource.receive()` call altogether, which may be considered as pausing for this inbound channel adapter until the `maxMessagesPerPoll` is changed to a non-zero value at a later time, e.g. via a Control Bus.
Also see <<./endpoint.adoc#global-default-poller>> for more information.
=====
[[channel-adapter-namespace-outbound]]
@@ -175,7 +177,6 @@ fun outboundChannelAdapterFlow(myPojo: MyPojo) =
If the channel being adapted is a `PollableChannel`, you must provide a poller sub-element (the `@Poller` sub-annotation on the `@ServiceActivator`), as the following example shows:
====
----
[source, java, role="primary"]
.Java
----

84
src/reference/asciidoc/endpoint.adoc
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@@ -95,18 +95,17 @@ The following example shows how to set the trigger:
----
PollingConsumer consumer = new PollingConsumer(channel, handler);
consumer.setTrigger(new IntervalTrigger(30, TimeUnit.SECONDS));
consumer.setTrigger(new PeriodicTrigger(30, TimeUnit.SECONDS));
----
====
Spring Integration currently provides two implementations of the `Trigger` interface: `IntervalTrigger` and `CronTrigger`.
The `IntervalTrigger` is typically defined with a simple interval (in milliseconds) but also supports an `initialDelay` property and a boolean `fixedRate` property (the default is `false` -- that is, no fixed delay).
The `PeriodicTrigger` is typically defined with a simple interval (in milliseconds) but also supports an `initialDelay` property and a boolean `fixedRate` property (the default is `false` -- that is, no fixed delay).
The following example sets both properties:
====
[source,java]
----
IntervalTrigger trigger = new IntervalTrigger(1000);
PeriodicTrigger trigger = new PeriodicTrigger(1000);
trigger.setInitialDelay(5000);
trigger.setFixedRate(true);
----
@@ -316,22 +315,87 @@ It is also possible to create top-level pollers, in which case only a `ref` attr
NOTE: The `ref` attribute is allowed only on the inner poller definitions.
Defining this attribute on a top-level poller results in a configuration exception being thrown during initialization of the application context.
====== Global Default Pollers
[[global-default-poller]]
====== Global Default Poller
To simplify the configuration even further, you can define a global default poller.
A single top-level poller within an `ApplicationContext` may have the `default` attribute set to `true`.
In that case, any endpoint with a `PollableChannel` for its input channel, that is defined within the same `ApplicationContext`, and has no explicitly configured `poller` sub-element uses that default.
A single top-level poller component in XML DSL may have the `default` attribute set to `true`.
For Java configuration a `PollerMetadata` bean with the `PollerMetadata.DEFAULT_POLLER` name must be declared in this case.
In that case, any endpoint with a `PollableChannel` for its input channel, that is defined within the same `ApplicationContext`, and has no explicitly configured `poller` uses that default.
The following example shows such a poller and a transformer that uses it:
[source,xml]
====
[source, java, role="primary"]
.Java DSL
----
<int:poller id="defaultPoller" default="true" max-messages-per-poll="5" fixed-rate="3000"/>
@Bean(name = PollerMetadata.DEFAULT_POLLER)
public PollerMetadata defaultPoller() {
PollerMetadata pollerMetadata = new PollerMetadata();
pollerMetadata.setMaxMessagesPerPoll(5);
pollerMetadata.setTrigger(new PeriodicTrigger(3000));
return pollerMetadata;
}
// No 'poller' attribute because there is a default global poller
@Bean
public IntegrationFlow transformFlow(MyTransformer transformer) {
return IntegrationFlows.from(MessageChannels.queue("pollable"))
.transform(transformer) // No 'poller' attribute because there is a default global poller
.channel("output")
.get();
}
----
[source, java, role="secondary"]
.Java
----
@Bean(PollerMetadata.DEFAULT_POLLER)
public PollerMetadata defaultPoller() {
PollerMetadata pollerMetadata = new PollerMetadata();
pollerMetadata.setMaxMessagesPerPoll(5);
pollerMetadata.setTrigger(new PeriodicTrigger(3000));
return pollerMetadata;
}
@Bean
public QueueChannel pollable() {
return new QueueChannel();
}
// No 'poller' attribute because there is a default global poller
@Transformer(inputChannel = "pollable", outputChannel = "output")
public Object transform(Object payload) {
...
}
----
[source, kotlin, role="secondary"]
.Kotlin DSL
----
@Bean(PollerMetadata.DEFAULT_POLLER)
fun defaultPoller() =
PollerMetadata()
.also {
it.maxMessagesPerPoll = 5
it.trigger = PeriodicTrigger(3000)
}
@Bean
fun convertFlow() =
integrationFlow(MessageChannels.queue("pollable")) {
transform(transformer) // No 'poller' attribute because there is a default global poller
channel("output")
}
----
[source, xml, role="secondary"]
.XML
----
<int:poller id="defaultPoller" default="true" max-messages-per-poll="5" fixed-delay="3000"/>
<!-- No <poller/> sub-element is necessary, because there is a default -->
<int:transformer input-channel="pollable"
ref="transformer"
output-channel="output"/>
----
====
[[transaction-support]]
====== Transaction Support
@@ -412,7 +476,7 @@ You should also keep in mind that the `task-executor` attribute can provide a re
The `executor` element shown earlier is provided for convenience.
As mentioned earlier in the <<endpoint-pollingconsumer,background section for polling consumers>>, you can also configure a polling consumer in such a way as to emulate event-driven behavior.
With a long `receive-timeout` and a short `interval-trigger`, you can ensure a very timely reaction to arriving messages even on a polled message source.
With a long receive timeout and a short interval in the trigger, you can ensure a very timely reaction to arriving messages even on a polled message source.
Note that this applies only to sources that have a blocking wait call with a timeout.
For example, the file poller does not block.
Each `receive()` call returns immediately and either contains new files or not.