Grails 2 has a plugin for Apache Camel called Routing but that plugin hasn’t been upgraded to Grails 3 yet. Luckily, Grails 3 is just Spring Boot so we can use the Camel Spring Boot component… with some caveats.

After you add the Camel component and a domain object or two, and do a grails run-app you will see something like this:

Field error in object 'Foo' on field 'version': rejected value [2.15.5]; codes [Foo.version.typeMismatch.error,Foo.version.typeMismatch,foo.version.typeMismatch.error,foo.version.typeMismatch,typeMismatch.Foo.version,typeMismatch.version,typeMismatch.java.lang.Long,typeMismatch]; arguments [version]; default message [Unable to parse number [2.15.5]

… and I was using Camel 2.15.5 in my project. Oh no… well it seems that Camel uses version in it’s Exchange metadata and it sees version in the domain objects and just inserts it’s version number there. No cool. To stop this, you need to add the following to your Grails 3 config:

grails:
   gorm:
      autowire: false

This will disable injecting beans into your domain classes… this is not something I do very often so I’m fine with it, but your use cases may vary.

After this, it’s pretty easy. I create a service with grails create-service Route then put the following in:

import org.apache.camel.builder.RouteBuilder;  

public class RouteService extends RouteBuilder {
    @Override
    public void configure() throws Exception {
        from("timer://foo?delay=1").to("log:bar?level=ERROR");
    }
}

And when you now run grails run-app you see that the route is running because you see these log messages.

ERROR bar - Exchange[ExchangePattern: InOnly, BodyType: null, Body: [Body is null]]
ERROR bar - Exchange[ExchangePattern: InOnly, BodyType: null, Body: [Body is null]]
ERROR bar - Exchange[ExchangePattern: InOnly, BodyType: null, Body: [Body is null]]
ERROR bar - Exchange[ExchangePattern: InOnly, BodyType: null, Body: [Body is null]]