Loading Java DSL routes from external JARs on Camel Quarkus

A common pattern when writing Camel applications is to have route configurations spread across one or more dependencies added to the application. For the Camel Java DSL, Camel Quarkus can discover RouteBuilder implementations at build time and automatically configure them for the CamelContext.

For example, consider a multi-module Maven project like this.

├── my-application
│   ├── pom.xml
│   └── src
│       └── main
│           └── java
│               └── org
│                   └── acme
│                       └── RoutesA.java
├── module-b
│   └── src
│       └── main
│           └── java
│               └── org
│                   └── acme
│                       └── RoutesB.java
└── module-c
    └── src
        └── main
            └── java
                └── org
                    └── acme
                        └── RoutesC.java

my-application/pom.xml has these dependencies defined.

<dependency>
    <groupId>org.acme</groupId>
    <artifactId>module-b</artifactId>
</dependency>
<dependency>
    <groupId>org.acme</groupId>
    <artifactId>module-c</artifactId>
</dependency>

You might expect that when running my-application, that the routes from RoutesB.java and RoutesC.java will be started.

However, this wont be the case. In order for those route classes to be discovered, the module-b and module-c JARs must contain a Jandex index.

Thankfully, this is a simple task that can achieved via any of the following methods.

1. jandex-maven-plugin

Add the following to your Maven module pom.xml to create a Jandex index.

<build>
  <plugins>
    <plugin>
      <groupId>io.smallrye</groupId>
      <artifactId>jandex-maven-plugin</artifactId>
      <version>3.2.0</version>
      <executions>
        <execution>
          <id>make-index</id>
          <goals>
            <goal>jandex</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

2. Empty beans.xml

Simply run the following to create an empty beans.xml file in your Maven module.

mkdir -p src/main/resources/META-INF
touch src/main/resources/META-INF/beans.xml

3. Quarkus configuration

In application.properties add.

# Index all dependencies with the Maven groupId of org.acme
quarkus.index-dependency.acme.group-id=org.acme

Conclusion

This brief summary hopefully helps to clear up any confusion when routes from external dependencies are not started in your application.

There's more information about Jandex here.

https://smallrye.io/jandex

There's more information about Quarkus dependency indexing strategies here.

https://quarkus.io/guides/cdi-reference#bean_discovery

Finally, you can find more information about Camel Quarkus route configuration here.

https://camel.apache.org/camel-quarkus/next/user-guide/defining-camel-routes.html

Happy coding!