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Chapter 94. Kura
Kura component
Kura component is available starting from Camel 2.15.
This documentation page covers the integration options of Camel with the Eclipse Kura M2M gateway. The common reason to deploy Camel routes into the Eclipse Kura is to provide enterprise integration patterns and Camel components to the messaging M2M gateway. For example you might want to install Kura on Raspberry PI, then read temperature from the sensor attached to that Raspberry PI using Kura services and finally forward the current temperature value to your data center service using Camel EIP and components.
KuraRouter activator
Bundles deployed to the Eclipse Kura are usually developed as bundle activators. So the easiest way to deploy Apache Camel routes into the Kura is to create an OSGi bundle containing the class extending
org.apache.camel.kura.KuraRouter class:
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
from("timer:trigger").
to("netty-http:http://app.mydatacenter.com/api");
}
}
Keep in mind that
KuraRouter implements the org.osgi.framework.BundleActivator interface, so you need to register its start and stop lifecycle methods while creating Kura bundle component class.
Kura router starts its own OSGi-aware
CamelContext. It means that for every class extending KuraRouter, there will be a dedicated CamelContext instance. Ideally we recommend to deploy one KuraRouter per OSGi bundle.
Deploying KuraRouter
Bundle containing your Kura router class should import the following packages in the OSGi manifest:
Import-Package: org.osgi.framework;version="1.3.0", org.slf4j;version="1.6.4", org.apache.camel,org.apache.camel.impl,org.apache.camel.core.osgi,org.apache.camel.builder,org.apache.camel.model, org.apache.camel.component.kura
Keep in mind that you don't have to import every Camel component bundle you plan to use in your routes, as Camel components are resolved as the services on the runtime level.
Before you deploy your router bundle, be sure that you have deployed (and started) the following Camel core bundles (using Kura GoGo shell)...
install file:///home/user/.m2/repository/org/apache/camel/camel-core/2.15.0/camel-core-2.15.0.jar start <camel-core-bundle-id> install file:///home/user/.m2/repository/org/apache/camel/camel-core-osgi/2.15.0/camel-core-osgi-2.15.0.jar start <camel-core-osgi-bundle-id> install file:///home/user/.m2/repository/org/apache/camel/camel-kura/2.15.0/camel-kura-2.15.0.jar start <camel-kura-bundle-id>
...and all the components you plan to use in your routes:
install file:///home/user/.m2/repository/org/apache/camel/camel-stream/2.15.0/camel-stream-2.15.0.jar start <camel-stream-bundle-id>
Then finally deploy your router bundle:
install file:///home/user/.m2/repository/com/example/myrouter/1.0/myrouter-1.0.jar start <your-bundle-id>
KuraRouter utilities
Kura router base class provides many useful utilities. This section explores each of them.
SLF4J logger
Kura uses SLF4J facade for logging purposes. Protected member
log returns SLF4J logger instance associated with the given Kura router.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
log.info("Configuring Camel routes!");
...
}
}BundleContext
Protected member
bundleContext returns bundle context associated with the given Kura router.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
ServiceReference<MyService> serviceRef = bundleContext.getServiceReference(LogService.class.getName());
MyService myService = bundleContext.getService(serviceRef);
...
}
}CamelContext
Protected member
camelContext is the CamelContext associated with the given Kura router.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
camelContext.getStatus();
...
}
}ProducerTemplate
Protected member
producerTemplate is the ProducerTemplate instance associated with the given Camel context.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
producerTemplate.sendBody("jms:temperature", 22.0);
...
}
}ConsumerTemplate
Protected member
consumerTemplate is the ConsumerTemplate instance associated with the given Camel context.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
producerTemplate.sendBody("jms:temperature", 22.0);
...
}
}OSGi service resolver
OSGi service resolver (
service(Class<T> serviceType)) can be used to easily retrieve service by type from the OSGi bundle context.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
MyService myService = service(MyService.class);
...
}
}
If service is not found, a
null value is returned. If you want your application to fail if the service is not available, use requiredService(Class) method instead. The requiredService throws IllegalStateException if a service cannot be found.
public class MyKuraRouter extends KuraRouter {
@Override
public void configure() throws Exception {
MyService myService = requiredService(MyService.class);
...
}
}KuraRouter activator callbacks
Kura router comes with the lifecycle callbacks that can be used to customize the way the Camel router works. For example to configure the
CamelContext instance associated with the router just before the former is started, override beforeStart method of the KuraRouter class:
public class MyKuraRouter extends KuraRouter {
...
protected void beforeStart(CamelContext camelContext) {
OsgiDefaultCamelContext osgiContext = (OsgiCamelContext) camelContext;
osgiContext.setName("NameOfTheRouter");
}
}Loading XML routes from ConfigurationAdmin
Sometimes it is desired to read the XML definition of the routes from the server configuration. This a common scenario for IoT gateways where over-the-air redeployment cost may be significant. To address this requirement each
KuraRouter looks for the kura.camel.BUNDLE-SYMBOLIC-NAME.route property from the kura.camel PID using the OSGi ConfigurationAdmin. This approach allows you to define Camel XML routes file per deployed KuraRouter. In order to update a route, just edit an appropriate configuration property and restart a bundle associated with it. The content of the kura.camel.BUNDLE-SYMBOLIC-NAME.route property is expected to be Camel XML route file, for example:
<routes xmlns="http://camel.apache.org/schema/spring">
<route id="loaded">
<from uri="direct:bar"/>
<to uri="mock:bar"/>
</route>
</routes>Deploying Kura router as a declarative OSGi service
If you would like to deploy your Kura router as a declarative OSGi service, you can use the
activate and deactivate methods provided by KuraRouter:
<scr:component name="org.eclipse.kura.example.camel.MyKuraRouter" activate="activate" deactivate="deactivate" enabled="true" immediate="true"> <implementation class="org.eclipse.kura.example.camel.MyKuraRouter"/> </scr:component>
