Spring Boot Web Reactive Starter

This experimental project provides a simple way to try the new Web Reactive support in Spring Framework 5.0.

Quickstart

Go to start.spring.io, set the Spring Boot version to 1.4+ and add the "Reactive Web" starter.

From there you can take a look at spring-boot-sample-web-reactive in this repository to see examples of reactive @Controllers and the reactive WebClient in use.

Server Runtime

By default this Boot Starter uses embedded Tomcat as the default server runtime.

Switching the server is easy. Simply exclude the Tomcat starter and add the dependency you want as shown here with Reactor Netty:

<dependency>
	<groupId>org.springframework.boot.experimental</groupId>
	<artifactId>spring-boot-starter-web-reactive</artifactId>
	<exclusions>
		<exclusion>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<dependency>
	<groupId>io.projectreactor.ipc</groupId>
	<artifactId>reactor-netty</artifactId>
</dependency>

An example of the same in Gradle and a switch to RxNetty:

compile('org.springframework.boot.experimental:spring-boot-starter-web-reactive') {
	exclude group: 'org.springframework.boot', module: 'spring-boot-starter-tomcat'
}
compile "io.reactivex:rxnetty-common"
compile "io.reactivex:rxnetty-http"

Below are the supported server runtimes. For the exact dependencies check out the sample project build:

• Reactor Netty
• Tomcat
• Jetty
• RxNetty
• Undertow

WebClient Dependencies

Spring Framework 5 also provides a reactive WebClient. For now the only supported HTTP client is Reactor Netty. Other HTTP clients such as Jetty and RxNetty will be added in the next milestone.

Resources

The Spring team has published a few blog posts on the subject:

• Reactive Spring
• Understanding Reactive types
• Notes on Reactive Programming part I, part II and part III

Known issues

This starter doesn't work with plain @SpringBootTests (i.e. with a WebEnvironment.MOCK, which is the default):

Caused by: java.lang.IllegalArgumentException: Unable to call initializer.
Object of class [org.springframework.boot.context.embedded.ReactiveWebApplicationContext]
must be an instance of interface org.springframework.web.context.ConfigurableWebApplicationContext

Web integration tests @SpringBootTests are working properly, for example @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT).

FAQ

I've found an issue, I have a question - where should I report it?

• You can report issues in this Github project or on https://jira.spring.io if this is a Spring Framework issue
• You can ask questions in Github issues as well or join the Gitter chat

Will this be available in Spring Boot? When?

Yes! Check out the Spring Boot milestones and especially the dedicated issue.

Is Spring Boot required to run Spring Web Reactive?

It certainly makes things easier, but it's not mandatory. For manual bootstrapping, please [read the reference documentation] (http://docs.spring.io/spring-framework/docs/5.0.0.BUILD-SNAPSHOT/spring-framework-reference/html/web-reactive.html#web-reactive-getting-started-manual).