CLI/Service Tutorial

This tutorial will show you how to create a CLI command to print the endpoints found by the reactive forwarding application from the Application tutorial. After completing this tutorial, you will understand:

• How to extend applications with new services
• How to extend the Karaf-based ONOS CLI with new commands

Offering services to other modules

If you want your module to be able to provide services to other modules, you should define a service interface and have your module class implement it.

1. Define a service interface.

We start by defining a new interface for the service in the same location as our application (~/onos-next/apps/ifwd/src/main/java/org/onlab/onos/ifwd/):

package org.onlab.onos.ifwd;

import java.util.Map;
import org.onlab.onos.net.HostId;

/**
 * A demonstrative service for the intent reactive forwarding application to
 * export
 */
public interface ForwardingMapService {

    /**
     * Get the endpoints of the host-to-host intents that were installed
     *
     * @return maps of source to destination
     */
    public Map<HostId, HostId> getEndPoints();

}

2. Import the service interface.

Next, we implement our service in IntentReactiveForwarding. We also indicate to Karaf that the application exports a service, using the the Felix SCR annotation @Service:

@Component(immediate = true)
@Service
public class IntentReactiveForwarding implements ForwardingMapService {

// ...<snip>...
 
    // the new service method, to be filled out
    @Override
    public Map<HostId, HostId> getEndPoints() {
        // TODO Auto-generated method stub
        return null;
    }
}

Although we won't be using it here in this manner, the @Service annotation enables another class to reference the service through the @Reference annotation:

@Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
protected ForwardingMapService fwdMapService;

3. Implement the service.

We can now define the new method.