CDI

Since Camel 2.10

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, FluentProducerTemplate, 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.

More details on how to test Camel CDI applications are available in Camel CDI testing.

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 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.

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 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.

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);
}

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
@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;

Camel context configuration

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

@ApplicationScoped
@Named("myCamelName")
class CustomCamelContext extends DefaultCamelContext {

}

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() {
        // Or set the Camel context name here
        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);
    }
}

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.:

Camel annotation CDI equivalent

Configuration property

 
@PropertyInject("key")
String value;

If using DeltaSpike configuration mechanism:

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

See configuration properties for more details.

Producer template injection (default Camel context)

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

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

@Produce("direct:outbound")
FluentProducerTemplate producer;

Endpoint injection

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

Bean injection (by type)

 
@BeanInject
MyBean bean;
 
@Inject
MyBean bean;

Bean injection (by name)

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

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 #bean:name notation.

The older syntax with just #name has been deprecated due to ambiguity as Camel supports a number of additional functions that start with the # notation.

If the URI parameter value starts with #bean: then Camel CDI will lookup for a bean of the given type by name, e.g.:

from("jms:queue:{{destination}}?transacted=true&transactionManager=#bean: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

Camel provides a set of 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
}

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
}

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.

CDI events endpoint

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);
}

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.

Transaction support

You must add camel-cdi-jta JAR as dependency for Camel CDI transaction support.

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.

Note that, for the time being, the transaction manager is looked up as JNDI resource with the following keys:

java:comp/TransactionManager
java:appserver/TransactionManager
java:pm/TransactionManager
java:/TransactionManager

Transaction policies

Camel CDI provides implementation for the typically supported Camel TransactedPolicy as CDI beans. It is possible to have these policies looked up by name using the transacted EIP, e.g.:

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");
    }
}

This would be equivalent to:

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");
    }
}

The list of supported transaction policy names is:

  • PROPAGATION_NEVER,

  • PROPAGATION_NOT_SUPPORTED,

  • PROPAGATION_SUPPORTS,

  • PROPAGATION_REQUIRED,

  • PROPAGATION_REQUIRES_NEW,

  • PROPAGATION_NESTED,

  • PROPAGATION_MANDATORY.

Transactional error handler

Camel CDI provides a transactional error handler that extends the redelivery error handler, forces a rollback whenever an exception occurs and creates a new transaction for each redelivery.

The camel-cdi-jta provides the CdiRouteBuilder class that exposes the transactionErrorHandler helper method to enable quick access to the configuration, e.g.:

class MyRouteBean extends CdiRouteBuilder {

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

Lazy Injection / Programmatic Lookup

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();

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
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