Chapter 59. Camel CDI

Camel CDI automatically deploys and configures a CamelContext bean. That CamelContext bean is automatically instantiated, configured and started (resp. stopped) when the CDI container initializes (resp. shuts down). It can be injected in the application, e.g.:

@Inject
CamelContext context;

That default CamelContext bean is qualified with the built-in @Default qualifier, is scoped @ApplicationScoped and is of type DefaultCamelContext.

Note that this bean can be customized programmatically and other Camel context beans can be deployed in the application as well.

Camel CDI automatically collects all the RoutesBuilder beans in the application, instantiates and add them to the CamelContext bean instance when the CDI container initializes. For example, adding a Camel route is as simple as declaring a class, e.g.:

class MyRouteBean extends RouteBuilder {
 
    @Override
    public void configure() {
        from("jms:invoices").to("file:/invoices");
    }
}

Note that you can declare as many RoutesBuilder beans as you want. Besides, RouteContainer beans are also automatically collected, instantiated and added to the CamelContext bean instance managed by Camel CDI when the container initializes.

Available as of Camel 2.19

In some situations, it may be necessary to disable the auto-configuration of the RouteBuilder and RouteContainer beans. That can be achieved by observing for the CdiCamelConfiguration event, e.g.:

static void configuration(@Observes CdiCamelConfiguration configuration) {
    configuration.autoConfigureRoutes(false);
}

Similarly, it is possible to deactivate the automatic starting of the configured CamelContext beans, e.g.:

static void configuration(@Observes CdiCamelConfiguration configuration) {
    configuration.autoStartContexts(false);
}

Camel CDI provides beans for common Camel primitives that can be injected in any CDI beans, e.g.:

@Inject
@Uri("direct:inbound")
ProducerTemplate producerTemplate;

@Inject
@Uri("direct:inbound")
FluentProducerTemplate fluentProducerTemplate;

@Inject
MockEndpoint outbound; // URI defaults to the member name, i.e. mock:outbound

@Inject
@Uri("direct:inbound")
Endpoint endpoint;

@Inject
TypeConverter converter;

If you just want to change the name of the default CamelContext bean, you can used the @ContextName qualifier provided by Camel CDI, e.g.:

@ContextName("camel-context")
class MyRouteBean extends RouteBuilder {
 
    @Override
    public void configure() {
        from("jms:invoices").to("file:/invoices");
    }
}

Else, if more customization is needed, any CamelContext class can be used to declare a custom Camel context bean. Then, the @PostConstruct and @PreDestroy lifecycle callbacks can be done to do the customization, e.g.:

@ApplicationScoped
class CustomCamelContext extends DefaultCamelContext {

    @PostConstruct
    void customize() {
        // Set the Camel context name
        setName("custom");
        // Disable JMX
        disableJMX();
    }

    @PreDestroy
    void cleanUp() {
        // ...
    }
}

Producer and disposer methods can also be used as well to customize the Camel context bean, e.g.:

class CamelContextFactory {

    @Produces
    @ApplicationScoped
    CamelContext customize() {
        DefaultCamelContext context = new DefaultCamelContext();
        context.setName("custom");
        return context;
    }

    void cleanUp(@Disposes CamelContext context) {
        // ...
    }
}

Similarly, producer fields can be used, e.g.:

@Produces
@ApplicationScoped
CamelContext context = new CustomCamelContext();

class CustomCamelContext extends DefaultCamelContext {

    CustomCamelContext() {
        setName("custom");
    }
}

This pattern can be used for example to avoid having the Camel context routes started automatically when the container initializes by calling the setAutoStartup method, e.g.:

@ApplicationScoped
class ManualStartupCamelContext extends DefaultCamelContext {

    @PostConstruct
    void manual() {
        setAutoStartup(false);
    }
}

Any number of CamelContext beans can actually be declared in the application as documented above. In that case, the CDI qualifiers declared on these CamelContext beans are used to bind the Camel routes and other Camel primitives to the corresponding Camel contexts. From example, if the following beans get declared:

@ApplicationScoped
@ContextName("foo")
class FooCamelContext extends DefaultCamelContext {
}

@ApplicationScoped
@BarContextQualifier
class BarCamelContext extends DefaultCamelContext {
}
 
@ContextName("foo")
class RouteAddedToFooCamelContext extends RouteBuilder {

    @Override
    public void configure() {
        // ...
    }
}
 
@BarContextQualifier
class RouteAddedToBarCamelContext extends RouteBuilder {

    @Override
    public void configure() {
        // ...
    }
}
 
@ContextName("baz")
class RouteAddedToBazCamelContext extends RouteBuilder {

    @Override
    public void configure() {
        // ...
    }
}
 
@MyOtherQualifier
class RouteNotAddedToAnyCamelContext extends RouteBuilder {

    @Override
    public void configure() {
        // ...
    }
}

The RoutesBuilder beans qualified with @ContextName are automatically added to the corresponding CamelContext beans by Camel CDI. If no such CamelContext bean exists, it gets automatically created, as for the RouteAddedToBazCamelContext bean. Note this only happens for the @ContextName qualifier provided by Camel CDI. Hence the RouteNotAddedToAnyCamelContext bean qualified with the user-defined @MyOtherQualifier qualifier does not get added to any Camel contexts. That may be useful, for example, for Camel routes that may be required to be added later during the application execution.

The CDI qualifiers declared on the CamelContext beans are also used to bind the corresponding Camel primitives, e.g.:

@Inject
@ContextName("foo")
@Uri("direct:inbound")
ProducerTemplate producerTemplate;

@Inject
@ContextName("foo")
@Uri("direct:inbound")
FluentProducerTemplate fluentProducerTemplate;

@Inject
@BarContextQualifier
MockEndpoint outbound; // URI defaults to the member name, i.e. mock:outbound

@Inject
@ContextName("baz")
@Uri("direct:inbound")
Endpoint endpoint;

To configure the sourcing of the configuration properties used by Camel to resolve properties placeholders, you can declare a PropertiesComponent bean qualified with @Named("properties"), e.g.:

@Produces
@ApplicationScoped
@Named("properties")
PropertiesComponent propertiesComponent() {
    Properties properties = new Properties();
    properties.put("property", "value");
    PropertiesComponent component = new PropertiesComponent();
    component.setInitialProperties(properties);
    component.setLocation("classpath:placeholder.properties");
    return component;
}

If you want to use DeltaSpike configuration mechanism you can declare the following PropertiesComponent bean:

@Produces
@ApplicationScoped
@Named("properties")
PropertiesComponent properties(PropertiesParser parser) {
    PropertiesComponent component = new PropertiesComponent();
    component.setPropertiesParser(parser);
    return component;
}

// PropertiesParser bean that uses DeltaSpike to resolve properties
static class DeltaSpikeParser extends DefaultPropertiesParser {
    @Override
    public String parseProperty(String key, String value, Properties properties) {
        return ConfigResolver.getPropertyValue(key);
    }
}

You can see the camel-example-cdi-properties example for a working example of a Camel CDI application using DeltaSpike configuration mechanism.

CDI beans annotated with the @Converter annotation are automatically registered into the deployed Camel contexts, e.g.:

@Converter
public class MyTypeConverter {

    @Converter
    public Output convert(Input input) {
        //...
    }
}

Note that CDI injection is supported within the type converters.

Available as of Camel 2.17

Camel provides a set of management events that can be subscribed to for listening to Camel context, service, route and exchange events. Camel CDI seamlessly translates these Camel events into CDI events that can be observed using CDI observer methods, e.g.:

void onContextStarting(@Observes CamelContextStartingEvent event) {
    // Called before the default Camel context is about to start
}

As of Camel 2.18, it is possible to observe events for a particular route (RouteAddedEvent, RouteStartedEvent, RouteStoppedEvent and RouteRemovedEvent) should it have an explicit defined, e.g.:

from("...").routeId("foo").to("...");

void onRouteStarted(@Observes @Named("foo") RouteStartedEvent event) {
    // Called after the route "foo" has started
}

When multiple Camel contexts exist in the CDI container, the Camel context bean qualifiers, like @ContextName, can be used to refine the observer method resolution to a particular Camel context as specified in observer resolution, e.g.:

void onRouteStarted(@Observes @ContextName("foo") RouteStartedEvent event) {
    // Called after the route 'event.getRoute()' for the Camel context 'foo' has started
}
 
void onContextStarted(@Observes @Manual CamelContextStartedEvent event) {
    // Called after the the Camel context qualified with '@Manual' has started
}

Similarly, the @Default qualifier can be used to observe Camel events for the default Camel context if multiples contexts exist, e.g.:

void onExchangeCompleted(@Observes @Default ExchangeCompletedEvent event) {
    // Called after the exchange 'event.getExchange()' processing has completed
}

In that example, if no qualifier is specified, the @Any qualifier is implicitly assumed, so that corresponding events for all the Camel contexts get received.

Note that the support for Camel events translation into CDI events is only activated if observer methods listening for Camel events are detected in the deployment, and that per Camel context.

Available as of Camel 2.17

The CDI event endpoint bridges the CDI events with the Camel routes so that CDI events can be seamlessly observed / consumed (resp. produced / fired) from Camel consumers (resp. by Camel producers).

The CdiEventEndpoint<T> bean provided by Camel CDI can be used to observe / consume CDI events whose event type is T, for example:

@Inject
CdiEventEndpoint<String> cdiEventEndpoint;

from(cdiEventEndpoint).log("CDI event received: ${body}");

This is equivalent to writing:

@Inject
@Uri("direct:event")
ProducerTemplate producer;

void observeCdiEvents(@Observes String event) {
    producer.sendBody(event);
}

from("direct:event").log("CDI event received: ${body}");

Conversely, the CdiEventEndpoint<T> bean can be used to produce / fire CDI events whose event type is T, for example:

@Inject
CdiEventEndpoint<String> cdiEventEndpoint;

from("direct:event").to(cdiEventEndpoint).log("CDI event sent: ${body}");

This is equivalent to writing:

@Inject
Event<String> event;

from("direct:event").process(new Processor() {
    @Override
    public void process(Exchange exchange) {
        event.fire(exchange.getBody(String.class));
    }
}).log("CDI event sent: ${body}");

Or using a Java 8 lambda expression:

@Inject
Event<String> event;

from("direct:event")
    .process(exchange -> event.fire(exchange.getIn().getBody(String.class)))
    .log("CDI event sent: ${body}");

The type variable T (resp. the qualifiers) of a particular CdiEventEndpoint<T> injection point are automatically translated into the parameterized event type (resp. into the event qualifiers) e.g.:

@Inject
@FooQualifier
CdiEventEndpoint<List<String>> cdiEventEndpoint;

from("direct:event").to(cdiEventEndpoint);

void observeCdiEvents(@Observes @FooQualifier List<String> event) {
    logger.info("CDI event: {}", event);
}

When multiple Camel contexts exist in the CDI container, the Camel context bean qualifiers, like @ContextName, can be used to qualify the CdiEventEndpoint<T> injection points, e.g.:

@Inject
@ContextName("foo")
CdiEventEndpoint<List<String>> cdiEventEndpoint;
// Only observes / consumes events having the @ContextName("foo") qualifier
from(cdiEventEndpoint).log("Camel context (foo) > CDI event received: ${body}");
// Produces / fires events with the @ContextName("foo") qualifier
from("...").to(cdiEventEndpoint);

void observeCdiEvents(@Observes @ContextName("foo") List<String> event) {
    logger.info("Camel context (foo) > CDI event: {}", event);
}

Note that the CDI event Camel endpoint dynamically adds an observer method for each unique combination of event type and event qualifiers and solely relies on the container typesafe observer resolution, which leads to an implementation as efficient as possible.

Besides, as the impedance between the typesafe nature of CDI and the dynamic nature of the Camel component model is quite high, it is not possible to create an instance of the CDI event Camel endpoint via URIs. Indeed, the URI format for the CDI event component is:

cdi-event://PayloadType<T1,...,Tn>[?qualifiers=QualifierType1[,...[,QualifierTypeN]...]]

With the authority PayloadType (resp. the QualifierType) being the URI escaped fully qualified name of the payload (resp. qualifier) raw type followed by the type parameters section delimited by angle brackets for payload parameterized type. Which leads to unfriendly URIs, e.g.:

cdi-event://org.apache.camel.cdi.example.EventPayload%3Cjava.lang.Integer%3E?qualifiers=org.apache.camel.cdi.example.FooQualifier%2Corg.apache.camel.cdi.example.BarQualifier

But more fundamentally, that would prevent efficient binding between the endpoint instances and the observer methods as the CDI container doesn’t have any ways of discovering the Camel context model during the deployment phase.

Available as of Camel 2.18

While CDI favors a typesafe dependency injection mechanism, it may be useful to reuse existing Camel XML configuration files into a Camel CDI application. In other use cases, it might be handy to rely on the Camel XML DSL to configure its Camel context(s).

You can use the @ImportResource annotation that’s provided by Camel CDI on any CDI beans and Camel CDI will automatically load the Camel XML configuration at the specified locations, e.g.:

@ImportResource("camel-context.xml")
class MyBean {
}

Camel CDI will load the resources at the specified locations from the classpath (other protocols may be added in the future).

Every CamelContext elements and other Camel primitives from the imported resources are automatically deployed as CDI beans during the container bootstrap so that they benefit from the auto-configuration provided by Camel CDI and become available for injection at runtime. If such an element has an explicit id attribute set, the corresponding CDI bean is qualified with the @Named qualifier, e.g., given the following Camel XML configuration:

<camelContext id="foo">
    <endpoint id="bar" uri="seda:inbound">
        <property key="queue" value="#queue"/>
        <property key="concurrentConsumers" value="10"/>
    </endpoint>
<camelContext/>

The corresponding CDI beans are automatically deployed and can be injected, e.g.:

@Inject
@ContextName("foo")
CamelContext context;

@Inject
@Named("bar")
Endpoint endpoint;

Note that the CamelContext beans are automatically qualified with both the @Named and @ContextName qualifiers. If the imported CamelContext element doesn’t have an id attribute, the corresponding bean is deployed with the built-in @Default qualifier.

Conversely, CDI beans deployed in the application can be referred to from the Camel XML configuration, usually using the ref attribute, e.g., given the following bean declared:

@Produces
@Named("baz")
Processor processor = exchange -> exchange.getIn().setHeader("qux", "quux");

A reference to that bean can be declared in the imported Camel XML configuration, e.g.:

<camelContext id="foo">
    <route>
        <from uri="..."/>
        <process ref="baz"/>
    </route>
<camelContext/>

Available as of Camel 2.19

Camel CDI provides support for Camel transactional client using JTA.

That support is optional hence you need to have JTA in your application classpath, e.g., by explicitly add JTA as a dependency when using Maven:

<dependency>
    <groupId>javax.transaction</groupId>
    <artifactId>javax.transaction-api</artifactId>
    <scope>runtime</scope>
</dependency>

You’ll have to have your application deployed in a JTA capable container or provide a standalone JTA implementation.

class MyRouteBean extends RouteBuilder {

    @Override
    public void configure() {
        from("activemq:queue:foo")
            .transacted("PROPAGATION_REQUIRED")
            .bean("transformer")
            .to("jpa:my.application.entity.Bar")
            .log("${body.id} inserted");
    }
}

class MyRouteBean extends RouteBuilder {

    @Inject
    @Named("PROPAGATION_REQUIRED")
    Policy required;

    @Override
    public void configure() {
        from("activemq:queue:foo")
            .policy(required)
            .bean("transformer")
            .to("jpa:my.application.entity.Bar")
            .log("${body.id} inserted");
    }
}

class MyRouteBean extends CdiRouteBuilder {

    @Override
    public void configure() {
        errorHandler(transactionErrorHandler()
            .setTransactionPolicy("PROPAGATION_SUPPORTS")
            .maximumRedeliveries(5)
            .maximumRedeliveryDelay(5000)
            .collisionAvoidancePercent(10)
            .backOffMultiplier(1.5));
    }
}

Available as of Camel 2.17

The Camel context beans are automatically adapted by Camel CDI so that they are registered as OSGi services and the various resolvers (like ComponentResolver and DataFormatResolver) integrate with the OSGi registry. That means that the Karaf Camel commands can be used to operate the Camel contexts auto-configured by Camel CDI, e.g.:

karaf@root()> camel:context-list
 Context        Status              Total #       Failed #     Inflight #   Uptime
 -------        ------              -------       --------     ----------   ------
 camel-cdi      Started                   1              0              0   1 minute

See the camel-example-cdi-osgi example for a working example of the Camel CDI OSGi integration.

While the CDI programmatic model favors a typesafe resolution mechanism that occurs at application initialization time, it is possible to perform dynamic / lazy injection later during the application execution using the programmatic lookup mechanism.

Camel CDI provides for convenience the annotation literals corresponding to the CDI qualifiers that you can use for standard injection of Camel primitives. These annotation literals can be used in conjunction with the javax.enterprise.inject.Instance interface which is the CDI entry point to perform lazy injection / programmatic lookup.

For example, you can use the provided annotation literal for the @Uri qualifier to lazily lookup for Camel primitives, e.g. for ProducerTemplate beans:

@Any
@Inject
Instance<ProducerTemplate> producers;

ProducerTemplate inbound = producers
    .select(Uri.Literal.of("direct:inbound"))
    .get();

Or for Endpoint beans, e.g.:

@Any
@Inject
Instance<Endpoint> endpoints;

MockEndpoint outbound = endpoints
    .select(MockEndpoint.class, Uri.Literal.of("mock:outbound"))
    .get();

Similarly, you can use the provided annotation literal for the @ContextName qualifier to lazily lookup for CamelContext beans, e.g.:

@Any
@Inject
Instance<CamelContext> contexts;

CamelContext context = contexts
    .select(ContextName.Literal.of("foo"))
    .get();

You can also refined the selection based on the Camel context type, e.g.:

@Any
@Inject
Instance<CamelContext> contexts;

// Refine the selection by type
Instance<DefaultCamelContext> context = contexts.select(DefaultCamelContext.class);

// Check if such a bean exists then retrieve a reference
if (!context.isUnsatisfied())
    context.get();

Or even iterate over a selection of Camel contexts, e.g.:

@Any
@Inject
Instance<CamelContext> contexts;

for (CamelContext context : contexts)
    context.setUseBreadcrumb(true);

Among the available Camel Maven archetypes, you can use the provided camel-archetype-cdi to generate a Camel CDI Maven project, e.g.:

mvn archetype:generate -DarchetypeGroupId=org.apache.camel.archetypes -DarchetypeArtifactId=camel-archetype-cdi

The Camel CDI component is compatible with any CDI 1.0, CDI 1.1 and CDI 1.2 compliant runtime. It’s been successfully tested against the following runtimes:

The following examples are available in the examples directory of the Camel project:

Camel CDI EAR deployments on {wildfly-camel} have some differences in class and resource loading behaviour, compared to standard WAR or JAR deployments.

{wildfly} bootstraps Weld using the EAR deployment ClassLoader. {wildfly} also mandates that only a single CDI extension is created and shared by all EAR sub-deployments.

This results in the 'Auto-configured' CDI Camel Context using the EAR deployment ClassLoader to dynamically load classes and resources. By default, this ClassLoader does not have access to resources within EAR sub-deployments.

For EAR deployments, it is recommended that usage of the 'Auto-configured' CDI Camel Context is avoided and that RouteBuilder classes are annotated with @ContextName, or that a CamelContext is created via the @ImportResource annotation or through CDI producer methods and fields. This helps {wildfly-camel} to determine the correct ClassLoader to use with Camel.