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Doc for binding dynamic destinations

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Resolves #710

Add simple example
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Ilayaperumal Gopinathan
2017-02-22 18:08:57 +05:30
committed by Marius Bogoevici
parent 347cac75f2
commit e029d4954e
1 changed files with 44 additions and 0 deletions
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spring-cloud-stream-core-docs/src/main/asciidoc/spring-cloud-stream-overview.adoc
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@@ -1115,6 +1115,50 @@ When native encoding is used, it is the responsibility of the consumer to use ap
Also, when native encoding/decoding is used the `headerMode` property is ignored and headers will not be embedded into the message.
+
Default: `false`.
[[dynamicdestination]]
== Binding producer to destinations dynamically at runtime
It is useful to have the Spring Cloud Stream 'outbound' applications sending messages to a 'destination' that is determined dynamically as the messages are processed at runtime.
In these cases, the destination names to the broker (for example: exchange name in case Rabbit or topic name in case of Kafka) may or may not be available beforehand.
Spring Cloud Stream applications can make use 'BinderAwareChannelResolver' which is available to the application when '@EnableBinding' is annotated to the application.
The property 'spring.cloud.stream.dynamicDestinations' can be set if the dynamic destinations are known and the application needs to bind to this list of dynamic destinations **only**. If this property is set to empty(which is by default empty), then 'BinderAwareChannelResolver' takes care of binding to all the resolved dynamic destinations.
For instance, the below example application registers a REST 'controller' with a request mapping on the path '/'. It uses the 'BinderAwareChannelResolver' that resolves the dynamic destinations using the SpEL expression evaluated against the message payload.
[source,java]
----
@EnableBinding
@Controller
public class SourceWithDynamicDestination {
@Autowired
private BinderAwareChannelResolver resolver;
@RequestMapping(path = "/", method = POST, consumes = "*/*")
@ResponseStatus(HttpStatus.ACCEPTED)
public void handleRequest(@RequestBody String body, @RequestHeader(HttpHeaders.CONTENT_TYPE) Object contentType) {
sendMessage(body, contentType);
}
private void sendMessage(String body, Object contentType) {
resolver.resolveDestination(body).send(MessageBuilder.createMessage(body,
new MessageHeaders(Collections.singletonMap(MessageHeaders.CONTENT_TYPE, contentType))));
}
}
----
Upon starting the application on the default port 8080, if the following data are sent:
----
curl -H "Content-Type: application/json" -X POST -d "customerId-1" http://localhost:8080
curl -H "Content-Type: application/json" -X POST -d "customerId-2" http://localhost:8080
----
The destinations 'customerId-1' and 'customerId-2' are created at the broker (for example: exchange in case of Rabbit or topic in case of Kafka with the names 'customerId-1' and 'customerId-2') and the data are published to the appropriate destinations dynamically.
[[contenttypemanagement]]
== Content Type and Transformation