source: josm/trunk/src/org/openstreetmap/josm/plugins/Plugin.java

// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.plugins;

import static org.openstreetmap.josm.tools.I18n.tr;

import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.List;

import org.openstreetmap.josm.data.Preferences;
import org.openstreetmap.josm.gui.MapFrame;
import org.openstreetmap.josm.gui.MapFrameListener;
import org.openstreetmap.josm.gui.download.DownloadSelection;
import org.openstreetmap.josm.gui.preferences.PreferenceSetting;
import org.openstreetmap.josm.spi.preferences.Config;
import org.openstreetmap.josm.spi.preferences.IBaseDirectories;
import org.openstreetmap.josm.tools.Logging;
import org.openstreetmap.josm.tools.Utils;

/**
 * For all purposes of loading dynamic resources, the Plugin's class loader should be used
 * (or else, the plugin jar will not be within the class path).
 * <p>
 * A plugin may subclass this abstract base class (but it is optional).
 * <p>
 * The actual implementation of this class is optional, as all functions will be called
 * via reflection. This is to be able to change this interface without the need of
 * recompiling or even breaking the plugins. If your class does not provide a
 * function here (or does provide a function with a mismatching signature), it will not
 * be called. That simple.
 * <p>
 * Or in other words: See this base class as an documentation of what automatic callbacks
 * are provided (you can register yourself to more callbacks in your plugin class
 * constructor).
 * <p>
 * Subclassing Plugin and overriding some functions makes it easy for you to keep sync
 * with the correct actual plugin architecture of JOSM.
 *
 * @author Immanuel.Scholz
 */
public abstract class Plugin implements MapFrameListener {

    /**
     * This is the info available for this plugin. You can access this from your
     * constructor.
     * <p>
     * (The actual implementation to request the info from a static variable
     * is a bit hacky, but it works).
     */
    private PluginInformation info;

    private final IBaseDirectories pluginBaseDirectories = new PluginBaseDirectories();

    private final class PluginBaseDirectories implements IBaseDirectories {
        private File preferencesDir;
        private File cacheDir;
        private File userdataDir;

        @Override
        public File getPreferencesDirectory(boolean createIfMissing) {
            if (preferencesDir == null) {
                preferencesDir = Config.getDirs().getPreferencesDirectory(createIfMissing).toPath()
                        .resolve("plugins").resolve(info.name).toFile();
            }
            if (createIfMissing && !preferencesDir.exists() && !preferencesDir.mkdirs()) {
                Logging.error(tr("Failed to create missing plugin preferences directory: {0}", preferencesDir.getAbsoluteFile()));
            }
            return preferencesDir;
        }

        @Override
        public File getUserDataDirectory(boolean createIfMissing) {
            if (userdataDir == null) {
                userdataDir = Config.getDirs().getUserDataDirectory(createIfMissing).toPath()
                        .resolve("plugins").resolve(info.name).toFile();
            }
            if (createIfMissing && !userdataDir.exists() && !userdataDir.mkdirs()) {
                Logging.error(tr("Failed to create missing plugin user data directory: {0}", userdataDir.getAbsoluteFile()));
            }
            return userdataDir;
        }

        @Override
        public File getCacheDirectory(boolean createIfMissing) {
            if (cacheDir == null) {
                cacheDir = Config.getDirs().getCacheDirectory(createIfMissing).toPath()
                        .resolve("plugins").resolve(info.name).toFile();
            }
            if (createIfMissing && !cacheDir.exists() && !cacheDir.mkdirs()) {
                Logging.error(tr("Failed to create missing plugin cache directory: {0}", cacheDir.getAbsoluteFile()));
            }
            return cacheDir;
        }
    }

    /**
     * Creates the plugin
     *
     * @param info the plugin information describing the plugin.
     */
    protected Plugin(PluginInformation info) {
        this.info = info;
    }

    /**
     * Replies the plugin information object for this plugin
     *
     * @return the plugin information object
     */
    public PluginInformation getPluginInformation() {
        return info;
    }

    /**
     * Sets the plugin information object for this plugin
     *
     * @param info the plugin information object
     */
    public void setPluginInformation(PluginInformation info) {
        this.info = info;
    }

    /**
     * Get the directories where this plugin can store various files.
     * @return the directories where this plugin can store files
     * @since 13007
     */
    public IBaseDirectories getPluginDirs() {
        return pluginBaseDirectories;
    }

    @Override
    public void mapFrameInitialized(MapFrame oldFrame, MapFrame newFrame) {}

    /**
     * Called in the preferences dialog to create a preferences page for the plugin,
     * if any available.
     * @return the preferences dialog, or {@code null}
     */
    public PreferenceSetting getPreferenceSetting() {
        return null;
    }

    /**
     * Called in the download dialog to give the plugin a chance to modify the list
     * of bounding box selectors.
     * @param list list of bounding box selectors
     */
    public void addDownloadSelection(List<DownloadSelection> list) {}

    /**
     * Get a class loader for loading resources from the plugin jar.
     *
     * This can be used to avoid getting a file from another plugin that
     * happens to have a file with the same file name and path.
     *
     * Usage: Instead of
     *   getClass().getResource("/resources/pluginProperties.properties");
     * write
     *   getPluginResourceClassLoader().getResource("resources/pluginProperties.properties");
     *
     * (Note the missing leading "/".)
     * @return a class loader for loading resources from the plugin jar
     */
    public ClassLoader getPluginResourceClassLoader() {
        File pluginDir = Preferences.main().getPluginsDirectory();
        File pluginJar = new File(pluginDir, info.name + ".jar");
        final URL pluginJarUrl = Utils.fileToURL(pluginJar);
        return AccessController.doPrivileged((PrivilegedAction<ClassLoader>)
                () -> new URLClassLoader(new URL[] {pluginJarUrl}, Plugin.class.getClassLoader()));
    }
}