docs/modules/ROOT/pages/cdi.adoc

= Contexts and Dependency Injection (CDI) in Camel Quarkus

CDI plays a central role in Quarkus and Camel Quarkus offers a first class support for it too.

You may use `@Inject`, `@ConfigProperty` and similar annotations e.g. to inject beans and configuration values to
your Camel `RouteBuilder`s. Here is the `RouteBuilder` from our `timer-log-cdi` xref:examples.adoc[example]:

[source,java]
----
import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;
import org.apache.camel.builder.RouteBuilder;
import org.eclipse.microprofile.config.inject.ConfigProperty;

@ApplicationScoped <1>
public class TimerRoute extends RouteBuilder {

    @ConfigProperty(name = "timer.period", defaultValue = "1s") <2>
    String period;

    @Inject
    Counter counter;

    @Override
    public void configure() throws Exception {
        fromF("timer:foo?period=%s", period)
                .setBody(exchange -> "Incremented the counter: " + counter.increment())
                .to("log:cdi-example?showExchangePattern=false&showBodyType=false");
    }
}
----

<1> The `@ApplicationScoped` annotation is required for `@Inject` and `@ConfigProperty` to work in a `RouteBuilder`.
Note that the `@ApplicationScoped` beans are managed by the CDI container and their life cycle is thus a bit more
complex than the one of the plain `RouteBuilder`. In other words, using `@ApplicationScoped` in `RouteBuilder`s comes
with some boot time penalty and you should therefore only annotate your `RouteBuilder` with `@ApplicationScoped` when
you really need it.

<2> The value for the `timer.period` property is defined in `src/main/resources/application.properties` of the example project.

TIP: Please refer to the https://quarkus.io/blog/quarkus-dependency-injection[Quarkus Dependency Injection guide] for more details.


== CDI and the Camel Bean component

=== Refer to a bean by name

To refer to a bean in a route definition by name, just annotate the the bean with `@Named("myNamedBean")` and
`@ApplicationScoped` (or some other
https://quarkus.io/guides/cdi-reference#supported_features[supported] scope). The `@RegisterForReflection` annotation
is important for the native mode.

[source,java]
----
import javax.enterprise.context.ApplicationScoped;
import javax.inject.Named;
import io.quarkus.runtime.annotations.RegisterForReflection;

@ApplicationScoped
@Named("myNamedBean")
@RegisterForReflection
public class NamedBean {
    public String hello(String name) {
        return "Hello " + name + " from the NamedBean";
    }
}
----

Then you can use the `myNamedBean` name in a route definition:

[source,java]
----
import org.apache.camel.builder.RouteBuilder;
public class CamelRoute extends RouteBuilder {
    @Override
    public void configure() {
        from("direct:named")
                .to("bean:namedBean?method=hello");
    }
}
----