Simantics Generic File Import is a utility service that enables [Eclipse's Dropins](http://help.eclipse.org/mars/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fmisc%2Fp2_dropins_format.html)-like functionality. The directory resides inside `~/workspace/.metadata/plugins/org.simantics.fileimport/dropins` and it is not watched by default. There are two ways to start the watchservice:

1. Call directly in Java `FileImportDropins.watchDropinsFolder()`
2. Use SCL function `watchDropinsFolder` from `"Dropins/Core"`

## Creating own File importer

To create own File importer it is usually enough to extend the abstract class `SimanticsResourceFileImport` and implement the two methods:

    /**
     * Returns a key-value map for file extensions this importer can handle
     *
     * @return Map<String, String> allowed extensions this service can handle. Key is the extension e.g. <code>.sharedLibrary</code> and the value is the description of the extension
     */
    Map<String, String> allowedExtensionsWithFilters();

    /*
     * Performs the import for the given file
     *
     * @param parent Resource parent of the imported entity in Simantics database
     * @param file Path file location of file
     * @return Optional Resource of the imported entity in Simantics database
     * @throws Exception
     */
    public abstract Optional<Resource> perform(Resource parent, Path file) throws Exception;

An example of such a class for importing FMU-files to Simantics workbench would be following:

~~~
public class FMIFileImport extends SimanticsResourceFileImport {

    private static final Map<String, String> EXTENSIONS_FILTERS = Collections.singletonMap("*.fmu",
            "Functional Mock-up Unit (*.fmu)");

    @Override
    public Optional<Resource> perform(Resource parent, Path file) throws IOException{
        try {
            Resource model = FMIStudioSCL.createFMIModel(parent, file);
            return Optional.of(model);
        } catch (FMILException | DatabaseException e) {
            e.printStackTrace();
            return Optional.empty();
        }
    }

    @Override
    public Map<String, String> allowedExtensionsWithFilters() {
        return EXTENSIONS_FILTERS;
    }

}
~~~

It is important to create the component for defining declarative service. To do this right click the same plugin where the implmentation is and click New -> Other -> Plug-in Development -> Component Definition.

Give the name for the XML file and and browse to the implementing class You just created.

An example of XML-file is:

<pre>
<?xml version="1.0" encoding="UTF-8"?>
<scr:component xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0" name="org.simantics.fmi.studio.fileimport">
   <implementation class="org.simantics.fmi.studio.fileimport.FMIFileImport"/>
   <service>
      <provide interface="org.simantics.fileimport.IGenericFileImport"/>
   </service>
</scr:component>
</pre>

## FileImportService utility class

The class `org.simantics.fileimport.FileImportService` contains utility methods for e.g. listing all current services and performing file imports:

~~~
    /**
     * Lists all supported file extensions which have a registered service for handling the import
     *
     * @return Map containing the extension and the description of the extension in that order
     */
    public static Map<String, String> supportedExtensionsWithFilters();

    /**
     * Method that performs the import of the given file. This method is called when e.g. {@link FileImportDropins} watcher detects {@link java.nio.file.StandardWatchEventKinds.ENTRY_CREATE} operation
     *
     * @param file Path file to be imported
     * @param callback Optional callback which can be used to catch Throwables thrown in the import process
     */
    public static void performFileImport(Path file, Optional<Consumer<Throwable>> callback);
~~~