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@ -38,33 +38,36 @@ server. The `WebTestClient` can be used for end-to-end integration tests too. |
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[[webflux-threading-model]] |
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=== Threading model |
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[[webflux-reactive-libraries]] |
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== Reactive Libraries |
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Reactor is a required dependency for the `spring-webflux` module and is used internally |
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for composing logic and for Reactive Streams support. An easy rule to remember is that |
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WebFlux APIs return `Flux` or `Mono` -- since that's what's used internally, and |
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leniently accept any Reactive Streams `Publisher` implementation. |
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The use of `Flux` and `Mono` helps to express cardinality -- e.g. |
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whether a single or multiple async values are expected. This is important for API design |
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but also essential in some cases, e.g. when encoding an HTTP message. |
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For annotated controllers, WebFlux adapts transparently to the reactive library in use |
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with proper translation of cardinality. This is done with the help of the |
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{api-spring-framework}/core/ReactiveAdapterRegistry.html[ReactiveAdapterRegistry] from |
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`spring-core` which provides pluggable support for reactive and async types. The registry |
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has built-in support for RxJava and `CompletableFuture` but others can be registered. |
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For functional endpoints, the `WebClient`, and other functional APIs, the general rule |
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of thumb for WebFlux APIs applies: |
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* `Flux` or `Mono` as return values -- use them to compose logic or pass to any Reactive |
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Streams library (both are `Publisher` implementations). |
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* Reactive Streams `Publisher` for input -- if a `Publisher` from another reactive library |
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is provided it can only be treated as a stream with unknown semantics (0..N). If the |
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semantics are known -- e.g. `io.reactivex.Single`, you can use `Mono.from(Publisher)` and |
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pass that in instead of the raw `Publisher`. |
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`spring-webflux` depends on `reactor-core` and uses it internally to compose asynchronous |
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logic and to provide Reactive Streams support. Generally WebFlux APIs return `Flux` or |
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`Mono` -- since that's what's used internally, and leniently accept any Reactive Streams |
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`Publisher` implementation as input. The use of `Flux` vs `Mono` is important because it |
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helps to express cardinality -- e.g. whether a single or multiple async values are |
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expected, and that can be essential for making decisions, for example when encoding or |
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decoding HTTP messages. |
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For annotated controllers, WebFlux transparently adapts to the reactive library chosen by |
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the application. This is done with the help of the |
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{api-spring-framework}/core/ReactiveAdapterRegistry.html[ReactiveAdapterRegistry] which |
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provides pluggable support for reactive library and other asynchronous types. The registry |
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has built-in support for RxJava and `CompletableFuture`, but others can be registered too. |
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For functional APIs such as <<webflux-fn>>, the `WebClient`, and others, the general rules |
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for WebFlux APIs apply -- `Flux` and `Mono` as return values, and Reactive Streams |
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`Publisher` as input. When a `Publisher`, whether custom or from another reactive library, |
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is provided, it can only be treated as a stream with unknown semantics (0..N). If however |
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the semantics are known, you can wrap it with `Flux` or `Mono.from(Publisher)` instead |
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of passing the raw `Publisher`. |
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[NOTE] |
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==== |
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