Developing a new Import Plugin

Providing an import plugin requires two main things. First and foremost you must implement the code for transforming service descriptions in the format you want to be able to import, to the ones MSM4J can handle. You should for this simply provide an implementation of the uk.ac.open.msm4j.io.ServiceTransformer interface.

Once implemented you should also provide a Guice module that ensures you declare your new implementation as a binding for ServiceTransformer. Given that many implementations of this method may be available at runtime, we make use of Guice's multibinding mechanism and index each implementation by the media type they support. Note that should there be service formats with the same media type, the engine will have no means to know how to choose the right one so be sure to chose a new one or remove the competing implementation from your classpath. Below you have a simple example on how such a Guice module should look like.

public class OwlsTransformationPlugin extends AbstractModule implements TransformationPluginModule {

    @Override
    protected void configure() {
        MapBinder<String,ServiceTransformer> binder = MapBinder.newMapBinder(binder(), String.class, ServiceTransformer.class);
        binder.addBinding(OwlsTransformer.mediaType).to(OwlsTransformer.class);
    }
}

The final thing required for the plugin to be automatically picked up by MSM4J is to provide the appropriate information for Java's ServiceLoader to locate your implementation. You should do this creating a file at META-INF/services/uk.ac.open.kmi.msm4j.io.TransformationPluginModule. The content of the file should just include a line with the complete name of your plugin implementation, eg., :

uk.ac.open.kmi.msm4j.transformer.OwlsTransformationPlugin

Developers using Maven can automate this last step easily by using serviceloader-maven-plugin. To do so, simply include the following in your plugin's POM file:

<!-- Generate the META-INF/services information for ServiceLoader -->
<plugin>
    <groupId>eu.somatik.serviceloader-maven-plugin</groupId>
    <artifactId>serviceloader-maven-plugin</artifactId>
    <version>1.0.2</version>
    <configuration>
        <services>
            <param>uk.ac.open.kmi.msm4j.io.TransformationPluginModule</param>
        </services>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

<dependency>
    <groupId>uk.ac.open.kmi.msm4j</groupId>
    <artifactId>msm4j-io</artifactId>
    <version>${project.version}</version>
</dependency>

<!--Add Guice for dependency injection -->
<dependency>
    <groupId>com.google.inject</groupId>
    <artifactId>guice</artifactId>
    <version>${guice.version}</version>
</dependency>

<dependency>
    <groupId>com.google.inject.extensions</groupId>
    <artifactId>guice-multibindings</artifactId>
    <version>${guice.version}</version>
</dependency>

// Obtain the transformation engine using Guice
Injector injector = Guice.createInjector(new TransformerModule());
ServiceTransformationEngine transformationEngine = injector.getInstance(ServiceTransformationEngine.class);
// Transform services
List<Services> services = transformationEngine.transform(file, null, OwlsTransformer.mediaType );