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GH-3946: Revise Router channelKeyFallback option (#3948)

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* GH-3946: Revise Router channelKeyFallback option

Fixes https://github.com/spring-projects/spring-integration/issues/3946

The `AbstractMappingMessageRouter` has both `resolutionRequired` and `channelKeyFallback`
as `true` by default.
End-users expects them to back off when they set a `defaultOutputChannel`.
They really want something similar to Java `switch` statement

* Change the logic in the `AbstractMappingMessageRouter` to reset `channelKeyFallback`
to `false` when `defaultOutputChannel` to avoid attempts to resolve channel from name,
but rather fallback to `defaultOutputChannel` as it states from th mentioned
Java `switch` statement experience
* Deprecate `RouterSpec.noChannelKeyFallback()` in favor of newly introduced `channelKeyFallback(boolean)`
* Call `channelKeyFallback(false)` from an overloaded `defaultOutputToParentFlow()`
to reflect the mentioned expected behavior in Java DSL as well.
* Respectively, deprecate `KotlinRouterSpec.noChannelKeyFallback()` wrapper
in favor of newly introduced `channelKeyFallback(channelKeyFallback: Boolean)`
* Remove redundant already `noChannelKeyFallback()` option in the `NoFallbackAllowedTests`
* Document the change and new behavior

* Fix `IntegrationGraphServerTests` to `setChannelKeyFallback(true)` explicitly

* Remove not relevant `default-output-channel` from the `DynamicRouterTests-context.xml`

* Reject an `AbstractMappingMessageRouter` configuration where `defaultOutputChannel` is provided
and both `channelKeyFallback` & `resolutionRequired` are set to `true`.
Such a state makes `defaultOutputChannel` as not reachable and may cause some confusions in target
applications.

* Remove `&` symbol from JavaDocs

* Fix `boolean` expression for `AbstractMappingMessageRouter` configuration check

* Fix `IntegrationGraphServerTests` for new router behavior

* Improve language in docs
This commit is contained in:
Artem Bilan
2022-11-16 14:19:26 -05:00
committed by GitHub
parent 60ba5444e7
commit e9257958fe
8 changed files with 139 additions and 28 deletions
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5
src/reference/asciidoc/router.adoc
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@@ -349,7 +349,10 @@ If set, this attribute provides a reference to the channel where messages should
If no default output channel is provided, the router throws an exception.
If you would like to silently drop those messages instead, set the default output channel attribute value to `nullChannel`.
+
NOTE: A message is sent only to the `default-output-channel` if `resolution-required` is `false` and the channel is not resolved.
NOTE: Starting with version 6.0, setting a default output channel also resets the `channelKeyFallback` option to `false`.
So, no attempts will be made to resolve a channel from its name, but rather fallback to this default output channel - similar to a Java `switch` statement.
If `channelKeyFallback` is set to `true` explicitly, the further logic depends on the `resolutionRequired` option: the message to non-resolved channel from key can reach a `defaultOutputChannel` only if `resolutionRequired` is `false`.
Therefore, a configuration where `defaultOutputChannel` is provided and both `channelKeyFallback` & `resolutionRequired` are set to `true` is rejected by the `AbstractMappingMessageRouter` initialization phase.
`resolution-required`::
This attribute specifies whether channel names must always be successfully resolved to channel instances that exist.

5
src/reference/asciidoc/whats-new.adoc
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@@ -110,6 +110,11 @@ For convenience, the XML and Java DSL for Scatter-Gather, based on the `Recipien
See <<./scatter-gather.adoc#scatter-gather,Scatter-Gather>> for more information.
Another convenient behavior change has been made to the `AbstractMappingMessageRouter`.
Now, setting a `defaultOutputChannel` also resets the `channelKeyFallback` property to `false`, so no attempts will be made to resolve a channel from its key, but the logic immediately falls back to sending the message to the `defaultOutputChannel`.
See <<./router.adoc#router-common-parameters-all,Router Options>> for more information.
The `AggregatingMessageHandler` now does not split a `Collection<Message<?>>` result of the `MessageGroupProcessor` (unless it is a `SimpleMessageGroupProcessor`) on the output, but emits a single message containing this whole collection as a payload.
See <<./aggregator.adoc#aggregator,Aggregator>> for more information.