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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 EndpointProducerTemplate 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, CamelContextStartedEventExchangeCompletedEvent, ...) as CDI events and provides a CDI events endpoint that can be used to consume / produce CDI events from / to Camel routes.

While the Camel CDI component is available as of Camel 2.10, it's been rewritten in Camel 2.17 to better fit into the CDI programming model. Hence some of the features like the Camel events to CDI events bridge and the CDI events endpoint only apply starting Camel 2.17.

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.:

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.:

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.

Auto-Configured Camel Primitives

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

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.:

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.:

 

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

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

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.:

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:

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.

Since Camel version 2.17.0, Camel CDI is capable of managing any kind of CamelContext beans. In previous versions, it is only capable of managing beans of type CdiCamelContext so it is required to extend it.

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

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.:

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

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

Auto-Configured Type Converters

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

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

If using DeltaSpike configuration mechanism:

See configuration properties for more details.

Producer template injection (default Camel context)

Endpoint injection (default Camel context)

Endpoint injection (Camel context by name)

Bean injection (by type)

Bean injection (by name)

POJO consuming

 

Bean Component

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

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

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.:

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

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

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.:

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

 

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

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:

This is equivalent to writing:

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

This is equivalent to writing:

 

Or using a Java 8 lambda expression:

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.:

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.:

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:

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.:

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.

Camel XML Configuration Import

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.:

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 run-time. 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:

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

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:

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

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.:

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

Lazy Injection / Programmatic Lookup

Available as of Camel 2.17

While the CDI programmatic model favors a type-safe 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:

 

 

Or for Endpoint beans, e.g.:

 

 

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

 

 

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

 

 

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

 

 

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.:

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:

Container

Version

Runtime

Weld SE

1.1.28.Final

CDI 1.0 / Java SE 7

OpenWebBeans

1.2.7

CDI 1.0 / Java SE 7

Weld SE

2.3.4.Final

CDI 1.2 / Java SE 7

OpenWebBeans

1.6.3

CDI 1.2 / Java SE 7

WildFly

8.2.1.Final

CDI 1.2 / Java EE 7

WildFly

9.0.1.Final

CDI 1.2 / Java EE 7

WildFly

10.0.0.Final

CDI 1.2 / Java EE 7

Karaf

2.4.4

CDI 1.2 / OSGi 4 / PAX CDI

Karaf

3.0.5

CDI 1.2 / OSGi 5 / PAX CDI

Karaf

4.0.4

CDI 1.2 / OSGi 6 / PAX CDI

Examples

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

Example

Description

camel-example-cdi

Illustrates how to work with Camel using CDI to configure components, endpoints and beans

camel-example-cdi-kubernetes

Illustrates the integration between Camel, CDI and Kubernetes

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-test

Demonstrates the testing features that are provided as part of the integration between Camel and 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-cdi-xml

Illustrates the use of Camel XML configuration files into a Camel CDI application

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

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