methods in java_generator.h/.cpp for generating two new types:

GenerateOSGiService - Generates interface class(s) (in java_package
directory) that has the same name as the rpc declaration in the
protofile.  For example:

service HealthCheck {
  // If the requested service is unknown, the call will fail with status
  // NOT_FOUND.
  rpc check(HealthCheckRequest) returns (HealthCheckResponse);
}

would generate a HealthCheck service interface class:

package io.grpc.health.v1;

public interface HealthCheck {

    public HealthCheckResponse check(HealthCheckRequest request);

}

Note that only blocking method calls (not streaming) are included in the
interface declaration.

GenerateOSGiAbstractImplService generates an abstract impl class that
implements the (e.g.) HealthCheck interface, with naming convention
Abstract<service name>Impl:

package io.grpc.health.v1;

import io.grpc.stub.StreamObserver;

public abstract class AbstractHealthCheckImpl extends
HealthCheckGrpc.HealthCheckImplBase implements HealthCheck {

    public abstract HealthCheckResponse check(HealthCheckRequest
request);

    public void check(HealthCheckRequest request,
StreamObserver<HealthCheckResponse> responseObserver) {
        responseObserver.onNext(check(request));
        responseObserver.onCompleted();
    }
}

Note that the impl of the grcp check/2 method calls the service
interface method check/1.

With the service interface method and the abstract service impl class,
it is easy for a remote service to be created as all that is needed is
to provide implementation for check/1 method in subclass.  Consumers of
the remote service use the interface only.

in service interface and in abstractserviceimpl class.

and abstract service interface impl