Using custom Camel components with Camel Quarkus

Sometimes you may want to use custom or third party Apache Camel components in your Camel Quarkus project.

If you add the component dependency to your project, you may find that when trying to use its endpoints that you encounter FailedToCreateRouteException, as your custom endpoint could not be found.

Fear not! The resolution is (usually) quite simple. Your custom component requires a Jandex index so that Camel Quarkus can discover it and work its build time optimization magic.

Indexing your component

Some options to index your component are as follows.

1. Maven plugins

You can create a Jandex index for your component JAR with the camel-component-maven-plugin.

<plugin>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-component-maven-plugin</artifactId>
  <version>${camel.version}</version>
  <executions>
    <execution>
      <id>generate</id>
      <goals>
        <goal>generate</goal>
      </goals>
      <phase>process-classes</phase>
    </execution>
   </executions>
</plugin>

The generate goal will create a Jandex index automatically. There's more information about the plugin in the documentation.

Alternatively, you can use the jandex-maven-plugin instead.

<plugin>
    <groupId>io.smallrye</groupId>
    <artifactId>jandex-maven-plugin</artifactId>
    <version>${jandex.version}</version>
    <executions>
        <execution>
            <id>make-index</id>
            <goals>
                <goal>jandex</goal>
            </goals>
        </execution>
    </executions>
</plugin>

2. Quarkus automatic Jandex indexing

If you cannot modify the component project to add Jandex indexing, then Quarkus can do it for you on-the-fly with some additional configuration in application.properties.

Replace my-custom-component with the Maven artifactId of your component.

quarkus.index-dependency.my-custom-component.group-id=org.acme
quarkus.index-dependency.my-custom-component.artifact-id=my-custom-component

3. Custom Quarkus extension

Unless you specifically want to target native mode compatibility for your component or generally want to make use of Quarkus build time optimizations, then one of the above two options should suffice.

Otherwise, you can create a custom Quarkus extension for your component. The process for creating an extension is covered extensively in the Quarkus Writing Extensions Guide.

Other potential problems

Camel service discovery

I mentioned above that a missing Jandex index is usually the cause of custom components not working on Camel Quarkus. Another potential issue is if the component makes use of Camel service discovery. E.g if there are some custom services defined under META-INF/services/org/apache/camel.

The core set of services automatically included by default are defined here. If your component uses a service not covered by those paths, then you'll need to add some additional configuration to your application.

For example, if you had a custom service defined under META-INF/services/org/apache/camel/my-custom, then you can add the following to application.properties.

quarkus.camel.service.discovery.include-patterns = META-INF/services/org/apache/camel/my-custom/*

Native mode compilation / runtime issues

If you choose to compile your application to a native executable, you may find that your component does not work as expected. The native compilation may fail, or you may encounter problems at runtime.

Some typical failures are due to classes that need to be registered for reflection. For that, you can use the quarkus.camel.native.reflection.include-patterns configuration property. Or if the component is loading resources from the classpath, those resources need to be embedded within the native application. To do that, you can use the quarkus.native.resources.includes configuration property.

More complex native mode issues may require you to consider writing a Quarkus extension. for your component.

Conclusion

Hopefully this brief overview helps to get your custom component working with Camel Quarkus. Feel free to contact the Camel Quarkus team with any issues and we'll try to resolve them.

Happy coding!