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@@ -4,6 +4,104 @@ This section goes into more detail about how you can work with Spring Cloud Stre
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It covers topics such as creating and running stream applications.
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--
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== What's New in 2.0?
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Spring Cloud Stream introduces quite a number of new features, enhancements and changes. The following sections outline most notable ones.
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=== New Features and Components
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==== Polling Consumer
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Introduction of _polled consumers_, where the application can control message processing rates. Please refer to the appropriate section for more details.
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You can also read this blog for more details https://spring.io/blog/2018/02/27/spring-cloud-stream-2-0-polled-consumers
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==== Micrometer support
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Metrics has been switched to use https://micrometer.io/[Micrometer]. `MeterRegistry` is also provided as a bean so custom application can autowire it to capture custom metrics.
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Please refer to the appropriate section for more details
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==== New Actuator Binding controls
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There are now new new Actuator binding controls to bothe visulaize as well as control Bindings lifecycle. By simply enabling actuator
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endpoints (e.g., --management.endpoints.web.exposure.include=*) one can now visualize bindings by simply accessing the following URL `http://<host>:<port>/actuator/bindings`.
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One can also _stop, start, pause_ and _resume_ bindings by posting to the following URL
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`curl -H "Content-Type: application/json" -X POST http://<host>:<port>/actuator/bindings/start/inOne` where 'inOne' is the name of the binding and 'start' is the
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operation to be performed.
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NOTE: _pause_ and _resume_ are only effective if corresponding binder and its underlyig technology supports it. Currently only Kafka binders support _pause_ and _resume_.
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==== Configurable RetryTemplate
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Aside from providing properties to configure `RetryTemplate` we now allow you to provide your own effectively overriding the one provided by the framework. Simply configure
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it as a `@Bean` in your application.
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=== Notable changes and enhancements
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==== Both Actuator and Web dependencies are now optional
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This helps to slim down the footprint of the deployed application in the event neither of the functionality is required.
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It also allows one to swicth between the reactive and conventional web paradigms by adding one of the following dependencies manually:
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[source,xml]
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----
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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</dependency>
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----
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or
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[source,xml]
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----
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-webflux</artifactId>
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</dependency>
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----
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Actuator dependency can be added as follows:
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[source,xml]
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----
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-actuator</artifactId>
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</dependency>
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----
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==== Content-type negotiation improvenents
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One of the core themes for 2.0 is improvements (both consistency and performance) around content-type negotiation and message conversion.
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The following summary outlines notable changes and improvements. Please refer to the appropriate section for more details as well as this blog
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https://spring.io/blog/2018/02/26/spring-cloud-stream-2-0-content-type-negotiation-and-transformation.
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* All message conversion is now handled *only* by `MessageConverters`.
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* Introduction of `@StreamMessageConverter` annotation to provide custom `MessageConverters`.
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* Introduction of the default _Content Type_ as `application/json` which needs to be taken into consideration when migrating 1.3
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application and/or operating in the mixed mode (i.e., 1.3 producer -> 2.0 consumer).
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* Messages with textual payloads and _contentType_ `text/...` or `.../json` are no longer converted to `Message<String>` for cases where argument type of the provided `MessageHandler`
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can not be determnied (i.e., `public void handle(Message<?> message)` or `public void handle(Object payload)`). Further more, a strong argument type may not be enough
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to properly convert messages, so `contentType` header is may be used as supplement by some `MessageConverters`.
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=== Notable Deprecations
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==== Java serialization (Java native and Kryo)
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* `JavaSerializationMessageConverter` and `KryoMessageConverter`. While these two converters remain for now, they will be moved out of the core packages and support in the future.
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The main reason for this deprecation is to signal the issue _type-based language-specific_ serialization couuld cause in the distributed environments, where Producers and Consumers
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may not only depend on different JVM versions or have different versions of supporting libraries (i.e., Kryo), but to also draw the attention to the fact that Consumers and Producers
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may and in a lot of cases are non-Java based.
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==== Deprecated classes and methods
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Following is a quick summary of notable deprecations. See corresponding javadocs fort more details.
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* `SharedChannelRegistry` in favor of `SharedBindingTargetRegistry`.
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* `Bindings` - beans qualified by it are already uniquely identified by their type. For example, provided `Source`, `Processor` or custom bindings:
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[source,java]
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----
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public interface Foo {
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String OUTPUT = "fooOutput";
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@Output(Foo.OUTPUT)
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MessageChannel output();
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}
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----
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* `HeaderMode.raw`. Use `none`, `headers` or `embeddedHeaders`
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* `ProducerProperties.partitionKeyExtractorClass` in favor of `partitionKeyExtractorName` and `ProducerProperties.partitionSelectorClass` in favor of `partitionSelectorName`.
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This is to ensure that both components are Spring configured/managed and referenced in Spring-friendly way.
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* `BinderAwareRouterBeanPostProcessor` - while the component exists it is no longer a Bean Post Processor and will be renamed in the future.
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* `BinderProperties.setEnvironment(Properties environment)` in favor of `BinderProperties.setEnvironment(Map<String, Object> environment)`.
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== Introducing Spring Cloud Stream
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Spring Cloud Stream is a framework for building message-driven microservice applications.
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Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications, and uses Spring Integration to provide connectivity to message brokers.
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Oleg Zhurakousky