Using Spring Boot Weblfux with embedded Tomcat

Question

I am attempting to use the WebFlux reactive types in a new Spring Boot App. I used the initializr at https://start.spring.io and selected the 2.0.0-SNAPSHOT version. I added the web reactive dependency and everything I did worked great. This was a really solid POC, the goal was how to make use of these types to modernize our APIs, to do this, we planned to slowly replace each portion of blocking and/or synchronous process and replace it with a non-blocking alternative implementation.

The problem I have is when I try to evolve my POC into something more akin to the services we have in production many things don't appear to be working. Now I understand that webflux is not GA yet, and that I shouldn't expect fully reactive support from all of the other spring projects yet. I do however recall when webflux was still called web-reactive that you could run on undertow/jetty/netty/tomcat/etc but now that I am using the webflux starter, everything defaults to netty, and I don't see the docs calling out how to change that to the embedded tomcat that our other services are currently using.

Is it still possible to use the spring-boot-starter-webflux with other app containers, or do I now need to manually bootstrap webflux to work with a something other than netty?

score 22 · Accepted Answer · answered Apr 25 '17 at 08:04

22

You can exclude spring-boot-starter-reactor-netty from the spring-boot-starter-webflux dependency and use spring-boot-starter-tomcat, spring-boot-starter-undertow or spring-boot-starter-jetty instead.

answered Apr 25 '17 at 08:04

Brian Clozel

56,583
15
167
176

2

Is that still valid? I'll end up with missing classes like `Caused by: java.lang.NoClassDefFoundError: io/netty/buffer/Unpooled` – Michael Simons Jul 02 '17 at 18:50
Should be. Could you create an issue on https://github.com/spring-projects/spring-boot/issues with the complete stacktrace? – Brian Clozel Jul 03 '17 at 08:05
So is spring-boot-starter-reactor-netty contains a server? Is Netty a server itself? From here: https://stackoverflow.com/a/35749512/10894456 I see Netty is not a server, or am I wrong? – J.J. Beam Mar 13 '21 at 09:05
Yes this starter ships with a client and a server. Netty supports both cases. – Brian Clozel Mar 14 '21 at 12:00

score 6 · Answer 2 · edited Dec 05 '22 at 16:26

If your objective is to use tomcat server then It is not necessary to exclude spring-boot-starter-reactor-netty. Adding spring boot starter tomcat will start the application in Tomcat server.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
    <exclusions>
        <!-- Exclude the Netty dependency -->
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-reactor-netty</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<!-- Use Tomcat instead -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-tomcat</artifactId>
</dependency>

Why do I have to include a webserver if all I wanna do is to consume web-services? — Chuck, Aug 11 '21 at 05:29

Using Spring Boot Weblfux with embedded Tomcat

2 Answers2