Spring MVC RxJava handlers

A Spring Boot starter for RxJava3 integration

Setup

Add the Spring Boot starter to your project:

maven :

<dependency>
	<groupId>io.iceflower</groupId>
	<artifactId>rxjava-spring-boot-starter</artifactId>
	<version>3.0.1</version>
</dependency>

gradle :

implementation 'io.iceflower:rxjava-spring-boot-starter:3.0.1'

Note:

You need to add jcenter repository.

Usage

Basic

Registers Spring's MVC return value handlers for io.reactivex.rxjava3.core.Observable and io.reactivex.rxjava3.core.Single types. You don't need to any longer use blocking operations or assign the values to DeferredResult or ListenableFuture instead you can declare that your REST endpoint returns Observable.

Example:

@RestController
public static class InvoiceResource {

    @RequestMapping(method = RequestMethod.GET, value = "/invoices", produces = MediaType.APPLICATION_JSON_VALUE)
    public Observable<Invoice> getInvoices() {

        return Observable.just(
                new Invoice("Acme", new Date()),
                new Invoice("Oceanic", new Date())
        );
    }
}

The Observable will wrap any produced results into a list and make it process through Spring's message converters. In case if you need to return exactly one result you can use io.reactivex.rxjava3.core.Single instead. You can think of io.reactivex.rxjava3.core.Single as counterpart of Spring's DeferredResult or ListenableFuture. Also with io.reactivex.rxjava3.core.Single, and unlike with io.reactivex.rxjava3.core.Observable it is possible to return ResponseEntity in order to have the control of the HTTP headers or the status code of the response.

Note: The HandlerReturnValueHandler for Observable uses 'toList' operator to aggregate the results, which is not workable with really long infinitive running Observables, from which is not possible to unsubscribe.

In some scenarios when you want to have more control over the async processing you can use either ObservableDeferredResult or SingleDeferredResult, those are the specialized implementation of DeferredResult allowing for instance of setting the processing timeout per response.

Server-sent events

Spring 4.2 introduced ResponseBodyEmitter for long-lived HTTP connections and streaming the response data. One of available specialized implementations is ObservableSseEmitter ,FlowableSseEmitter that allows to send server sent event produced from io.reactivex.rxjava3.core.Observable, io.reactivex.rxjava3.core.Flowable.

Example of ObservableSseEmitter:

@RestController
public static class Events {

    @RequestMapping(method = RequestMethod.GET, value = "/messages")
    public ObservableSseEmitter<String> messages() {
        return new ObservableSseEmitter<String>(
            Observable.just(
                "message 1", "message 2", "message 3"
            )
        );
    }
}

Example of FlowableSseEmitter:

@RestController
public static class Events {

    @RequestMapping(method = RequestMethod.GET, value = "/messages")
    public FlowableSseEmitter<String> messages() {
        return new FlowableSseEmitter<String>(
            Observable.just(
                "message 1", "message 2", "message 3"
            )
        );
    }
}

This will output:

data: message 1

data: message 2

data: message 3

The SSE can be conveniently consumed by a JavaScript client for instance.

Properties

The only supported property is rxjava.mvc.enabled which allows to disable this extension.

rxjava.mvc.enabled=true # true by default

License

Apache 2.0

Note : The source code for this repository is a modification of some of the original author's code for maintenance purposes.

origin code : https://github.com/jmnarloch/rxjava-spring-boot-starter