Developing a new EMC Driver

This article demonstrates the implementation of "drivers" for Epsilon's Model Connectivity layer.

YAML Driver

The following training session recording and deck of slides demonstrate the implementation of Epsilon's YAML driver. The complete source-code is located in Epsilon's Git repository.

CSV Pro Driver

The slides below demonstrate the implementation of an alternative driver for CSV files, located under the examples folder of Epsilon's repository.

Filesystem Driver

This is a minimal toy driver where filesystem folders represent types and property files contained in them represent model elements that are their instances. Below is the main class of the driver and the full source code in Epsilon's repository.

FilesystemModel.java

/*********************************************************************
* Copyright (c) 2008 The University of York.
*
* This program and the accompanying materials are made
* available under the terms of the Eclipse Public License 2.0
* which is available at https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
**********************************************************************/
package org.eclipse.epsilon.emc.filesystem;

import java.io.File;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.eclipse.epsilon.eol.exceptions.EolRuntimeException;
import org.eclipse.epsilon.eol.exceptions.models.EolEnumerationValueNotFoundException;
import org.eclipse.epsilon.eol.exceptions.models.EolModelElementTypeNotFoundException;
import org.eclipse.epsilon.eol.exceptions.models.EolModelLoadingException;
import org.eclipse.epsilon.eol.exceptions.models.EolNotInstantiableModelElementTypeException;
import org.eclipse.epsilon.eol.execute.introspection.IPropertyGetter;
import org.eclipse.epsilon.eol.execute.introspection.IPropertySetter;
import org.eclipse.epsilon.eol.models.Model;


public class FilesystemModel extends Model {

    // Map of directories -> files they contain
    protected Map<File, List<File>> cache = new HashMap<>();

    public FilesystemModel(File root) {
        populateCache(root, cache);
    }

    @Override
    public boolean hasType(String type) {
        return directoryForName(type) != null;
    }

    @Override
    public Collection<?> getAllOfKind(String type)
            throws EolModelElementTypeNotFoundException {
        return cache.get(directoryForName(type));
    }

    @Override
    public boolean owns(Object instance) {
        for (File directory : cache.keySet()) {
            if (cache.get(directory).contains(instance)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public IPropertyGetter getPropertyGetter() {
        return new FilesystemModelPropertyGetter();
    }

    @Override
    public IPropertySetter getPropertySetter() {
        return new FilesystemModelPropertySetter();
    }

    @Override
    public Collection<?> getAllOfType(String type)
            throws EolModelElementTypeNotFoundException {

        return cache.get(directoryForName(type));
    }

    //TODO: Implement

    @Override
    public void load() throws EolModelLoadingException {

    }

    @Override
    public Object getEnumerationValue(String enumeration, String label)
            throws EolEnumerationValueNotFoundException {
        return null;
    }

    @Override
    public Collection<?> allContents() {
        return null;
    }

    @Override
    public String getTypeNameOf(Object instance) {
        return null;
    }

    @Override
    public Object createInstance(String type)
            throws EolModelElementTypeNotFoundException,
            EolNotInstantiableModelElementTypeException {
        return null;
    }

    @Override
    public Object getElementById(String id) {
        return null;
    }

    @Override
    public String getElementId(Object instance) {
        return null;
    }

    @Override
    public void setElementId(Object instance, String newId) {

    }

    @Override
    public void deleteElement(Object instance) throws EolRuntimeException {

    }

    @Override
    public boolean isInstantiable(String type) {
        return false;
    }

    @Override
    public boolean store(String location) {
        return false;
    }

    @Override
    public boolean store() {
        return false;
    }

    protected File directoryForName(String name) {
        for (File directory : cache.keySet()) {
            if (directory.getName().equals(name)) {
                return directory;
            }
        }
        return null;
    }

    protected void populateCache(File file, Map<File, List<File>> cache) {

        if (file.isDirectory()) {
            ArrayList<File> files = new ArrayList<>();
            for (File child : file.listFiles()) {
                if (child.isFile()) {
                    files.add(child);
                }
                else {
                    populateCache(child, cache);
                }
            }
            cache.put(file, files);
        }
    }

}