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Eclipse Kura component

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.

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KuraRouter activator

The 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 bundles 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.

...

install file:///home/user/.m2/repository/org/apache/camel/camel-stream/2.15.0/camel-stream-2.15.0.jar
start <camel-kurastream-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>

Auto-configured consumer and producer templates

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.Camel auto-configuration provides a pre-configured ConsumerTemplate and ProducerTemplate instances. You can simply inject them into your Spring-managed beans:

@Component
public class InvoiceProcessorMyKuraRouter extends KuraRouter {

  @Autowired
  private ProducerTemplate producerTemplate;
@Override
  @Autowired
  private ConsumerTemplate consumerTemplate;
  public void processNextInvoiceconfigure() throws Exception {
    Invoice invoice = consumerTemplate.receiveBody("jms:invoices", Invoice.class		log.info("Configuring Camel routes!");
    ...
    producerTemplate.sendBody("netty-http:http://invoicing.com/received/" + invoice.id());
...
    }

}

By default consumer and producer templates comes with the endpoint cache sizes equal to 1000. You can change that values via the following Spring properties:

...

camel.springboot.consumerTemplateCacheSize = 100
camel.springboot.producerTemplateCacheSize = 200

BundleContext

Protected member bundleContext returns bundle context associated with the given Kura router.

Auto-configured TypeConverter

Camel auto-configuration registers TypeConverter instance named typeConverter in the Spring context.

@Component
public class InvoiceProcessorMyKuraRouter extends KuraRouter {

  @Autowired
  private@Override
 TypeConverter typeConverter;

  public longvoid parseInvoiceValueconfigure(Invoice invoice)) throws Exception {
		ServiceReference<MyService> serviceRef =  String invoiceValue = invoice.grossValue(bundleContext.getServiceReference(LogService.class.getName());
		MyService myService = bundleContext.getService(serviceRef);
    return    typeConverter..convertTo(Long.class, invoiceValue);
.
    }

}

Spring type conversion API bridge

CamelContext

Protected member camelContext is the CamelContext associated with the given Kura router.Spring comes with the powerful type conversion API. Spring API happens not to be much different from the Camel type converter API. As those APIs are so similar, Camel Spring Boot automatically registers bridge converter (SpringTypeConverter) that delegates to the Spring conversion API. It basically means that out-of-the-box Camel will threat Spring Converters as Camel ones. With this approach you can enjoy both Camel and Spring converters accessed via Camel TypeConverter API:

@Component
public class MyKuraRouter InvoiceProcessorextends KuraRouter {

  @Autowired
  private@Override
 TypeConverter typeConverter;

  public UUIDvoid parseInvoiceIdconfigure(Invoice invoice) {) throws Exception {
		camelContext.getStatus();
    // Using Spring's StringToUUIDConverter
    UUID id = invoice.typeConverter.convertTo(UUID.class, invoice.getId());
.
    }

}

Under the hood Camel Spring Boot delegates conversion to the Spring's ConversionService instances available in the application context. If no ConversionService instance is available, Camel Spring Boot auto-configuration will create one for you.

Disabling type conversions features

If you don't want Camel Spring Boot to register type-conversions related features (like TypeConverter instance or Spring bridge) set the camel.springboot.typeConversion property to false.

...

camel.springboot.typeConversion = false

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.

Fat jars and fat wars

The easiest way to create Camel-aware Spring Boot fat jar/war is to extend the org.apache.camel.spring.boot.FatJarRouter class...

package com.example;
 
... // imports
 
@SpringBootApplication
public class MyFatJarRouterMyKuraRouter extends FatJarRouterKuraRouter {

    @Override
    public void configure() throws Exception {
		double currentTemperature       from("netty-http:http://0.0.0.0:18080").= producerTemplate.receiveBody("jms:temperature", Double.class);
        ...
    setBody().simple("ref:helloWorld");
    }}

}

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 {

    @Bean@Override
    public Stringvoid helloWorldconfigure() throws Exception {
		MyService myService = service(MyService.class);
     return "helloWorld";   ...
    }

}

...and add the following property to your application.properties file:

...

spring.main.sources = com.example.MyFatJarRouter

It is also recommended to define your main class explicitly in the Spring Boot Maven plugin configuration: 

...

 <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <version>${spring-boot.version}</version>
    <configuration>
      <mainClass>com.example.MyFatJarRouter</mainClass>
    </configuration>
    <executions>
      <execution>
        <goals>
          <goal>repackage</goal>
        </goals>
      </execution>
    </executions>
</plugin>

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 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>

In order to turn your fat jar into fat war, add the following class extending  org.apache.camel.spring.boot.FatWarInitializer to your project:

package com.example;
 
... // imports

public class MyFatWarInitializer extends FatWarInitializer {


  @Override
  protected Class<? extends FatJarRouter> routerClass() {
    return MyFatJarRouter.class;
  }

}