CDI

Camel CDI

The Camel CDI component provides auto-configuration for Apache Camel using CDI as dependency injection framework based on convention-over-configuration. It auto-detects Camel routes available in the application and provides beans for common Camel primitives like Endpoint, ProducerTemplate or TypeConverter. It implements standard Camel bean integration so that Camel annotations like @Consume, @Produce and @PropertyInject can be used seamlessly in CDI beans. Besides, it bridges Camel events (e.g. RouteAddedEvent, CamelContextStartedEvent, ExchangeCompletedEvent, ...) as CDI events and provides a CDI events endpoint that can be used to consume / produce CDI events from / to Camel routes.

Auto-configured Camel context

Camel CDI automatically deploys and configures a CamelContext bean. That CamelContext bean is automatically instantiated, configured and started (resp. stopped) when the CDI container initialises (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 customised programmatically and other Camel context beans can be deployed in the application as well.

Auto-detecting Camel routes

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

class MyRouteBean extends RoutesBuilder {
 
	@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 initialises.

Auto-configured Camel primitives

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

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

@Inject
TypeConverter converter;

Camel context configuration

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 RoutesBuilder {
 
	@Override
    public void configure() {
        from("jms:invoices").to("file:/invoices");
    }
}

Else, if more customisation 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 customisation, 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 initialises by calling the setAutoStartup method, e.g.:

@ApplicationScoped
class ManualStartupCamelContext extends DefaultCamelContext {

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

Multiple Camel contexts

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 RouteAdddedToFooCamelContext extends RouteBuilder {
 
	@Override
    public void configure() {
        // ...
    }
}
 
@BarContextQualifier
class RouteAdddedToBarCamelContext extends RouteBuilder {
 
	@Override
    public void configure() {
        // ...
    }
}
 
@ContextName("baz")
class RouteAdddedToBazCamelContext 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
@BarContextQualifier
MockEndpoint outbound; // URI defaults to the member name, i.e. mock:outbound

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

Configuration properties

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);
    }
}

Auto-configured type converters

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.

Camel bean integration

Camel annotations

As part of the Camel bean integration, Camel comes with a set of annotations that are seamlessly supported by Camel CDI. So you can use any of these annotations in your CDI beans, e.g.:

@PropertyInject("key")
String value;

@Inject
@ConfigProperty(name = "key")
String value;

@Produce(uri = "mock:outbound")
ProducerTemplate producer;

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

@EndpointInject(uri = "direct:inbound")
Endpoint endpoint;

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

@EndpointInject(uri = "direct:inbound", context = "foo")
Endpoint contextEndpoint;

@Inject
@ContextName("foo")
@Uri("direct:inbound")
Endpoint contextEndpoint;

@BeanInject
MyBean bean;

@Inject
MyBean bean;

@BeanInject("foo")
MyBean bean;

@Inject
@Named("foo")
MyBean bean;

@Consume(uri = "seda:inbound")
void consume(@Body String body) {
    //...
}

Bean component

You can refer to CDI beans, either by type or name, From the Camel DSL, e.g. with the Java Camel DSL:

class MyBean {
	//...
}
 
from("direct:inbound").bean(MyBean.class);

Or to lookup a CDI bean by name from the Java DSL:

@Named("foo")
class MyNamedBean {
	//...
}
 
from("direct:inbound").bean("foo");

Referring beans from Endpoint URIs

When configuring endpoints using the URI syntax you can refer to beans in the Registry using the # notation. If the URI parameter value starts with a # sign then Camel CDI will lookup for a bean of the given type by name, e.g.:

from("jms:queue:{{destination}}?transacted=true&transactionManager=#jtaTransactionManager").to("...");

Having the following CDI bean qualified with @Named("jtaTransactionManager"):

@Produces
@Named("jtaTransactionManager")
PlatformTransactionManager createTransactionManager(TransactionManager transactionManager, UserTransaction userTransaction) {
    JtaTransactionManager jtaTransactionManager = new JtaTransactionManager();
    jtaTransactionManager.setUserTransaction(userTransaction);
    jtaTransactionManager.setTransactionManager(transactionManager);
    jtaTransactionManager.afterPropertiesSet();
    return jtaTransactionManager;
}

Camel events to CDI events

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
}

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
}

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.

CDI events endpoint

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}");

@Inject
Event<String> event;

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

@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.

Auto-configured OSGi integration

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.

Maven Archetype

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

Supported containers

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:

Examples

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

• camel-example-cdi - illustrates how to work with Camel using CDI to configure components, endpoints and beans,
• camel-example-cdi-metrics - illustrates the integration between Camel, Dropwizard Metrics and CDI,
• camel-example-cdi-properties - illustrates the integration between Camel, DeltaSpike and CDI for configuration properties,
• camel-example-cdi-osgi - a CDI application using the SJMS component that can be executed inside an OSGi container using PAX CDI,
• camel-example-cdi-rest-servlet - illustrates the Camel REST DSL being used in a Web application that uses CDI as dependency injection framework,
• camel-example-widget-gadget-cdi - the Widget and Gadget use-case from the EIP book implemented in Java with CDI dependency Injection,
• camel-example-swagger-cdi - an example using REST DSL and Swagger Java with CDI.

See Also

• CDI Web site
• CDI ecosystem
• Going further with CDI (See Camel CDI section)