uniol.apt.io.renderer.AbstractRenderers.java Source code

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Here is the source code for uniol.apt.io.renderer.AbstractRenderers.java

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/*-
 * APT - Analysis of Petri Nets and labeled Transition systems
 * Copyright (C) 2015       vsp
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

package uniol.apt.io.renderer;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.apache.commons.io.IOUtils;
import org.apache.commons.io.LineIterator;

/**
 * Class which provides the correct renderer for a given format.
 *
 * @author vsp
 *
 * @param <T> The class which the renderers should render.
 */
public class AbstractRenderers<T> implements Renderers<T> {
    private Map<String, Renderer<T>> renderers;

    /**
     * Constructor
     *
     * @param clazz Class object of the which the renderers should render
     */
    @SuppressWarnings("unchecked") // I hate type erasure and other java things ...
    protected AbstractRenderers(Class<T> clazz) {
        this.renderers = new HashMap<>();

        String className = clazz.getCanonicalName();

        ClassLoader cl = getClass().getClassLoader();
        try {
            Enumeration<URL> rendererNames = cl.getResources(
                    "META-INF/uniol/apt/compiler/" + Renderer.class.getCanonicalName() + "/" + className);

            while (rendererNames.hasMoreElements()) {
                try (InputStream is = rendererNames.nextElement().openStream()) {
                    LineIterator lIter = IOUtils.lineIterator(is, "UTF-8");
                    while (lIter.hasNext()) {
                        String rendererName = lIter.next();
                        Class<? extends Renderer<T>> rendererClass;
                        try {
                            rendererClass = (Class<? extends Renderer<T>>) cl.loadClass(rendererName);
                        } catch (ClassNotFoundException ex) {
                            throw new RuntimeException(String.format("Could not load class %s", rendererName), ex);
                        }
                        Renderer<T> renderer;
                        try {
                            renderer = rendererClass.newInstance();
                        } catch (ClassCastException | IllegalAccessException | InstantiationException ex) {
                            throw new RuntimeException(String.format("Could not instantiate %s", rendererName), ex);
                        }
                        String format = renderer.getFormat();
                        if (format == null || format.equals("") || !format.equals(format.toLowerCase())) {
                            throw new RuntimeException(String.format("Renderer %s reports an invalid format: %s",
                                    rendererName, format));
                        }
                        Renderer<T> oldRenderer = this.renderers.get(format);
                        if (oldRenderer != null && !oldRenderer.getClass().equals(rendererClass)) {
                            throw new RuntimeException(String.format(
                                    "Different renderers claim, to interpret format %s:" + " %s and %s", format,
                                    oldRenderer.getClass().getCanonicalName(), rendererName));
                        }
                        this.renderers.put(format, renderer);
                    }
                }
            }
        } catch (IOException ex) {
            throw new RuntimeException("Failed to discover renderers", ex);
        }

    }

    @Override
    public Renderer<T> getRenderer(String format) throws RendererNotFoundException {
        Renderer<T> renderer = this.renderers.get(format.toLowerCase());
        if (renderer == null) {
            throw new RendererNotFoundException(String.format("Renderer for format %s not found", format));
        }
        return renderer;
    }

    @Override
    public Set<String> getSupportedFormats() {
        return this.renderers.keySet();
    }
}

// vim: ft=java:noet:sw=8:sts=8:ts=8:tw=120