org.eclipse.smila.search.plugin.PluginFactory.java Source code

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Here is the source code for org.eclipse.smila.search.plugin.PluginFactory.java

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/***********************************************************************************************************************
 * Copyright (c) 2008 empolis GmbH and brox IT Solutions GmbH. All rights reserved. This program and the accompanying
 * materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors: August Georg Schmidt (brox IT Solutions GmbH) - initial API and implementation
 **********************************************************************************************************************/
package org.eclipse.smila.search.plugin;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.Platform;
import org.eclipse.smila.search.EIFActivator;

/**
 * @author GSchmidt
 * 
 * To change this generated comment go to Window>Preferences>Java>Code Generation>Code and Comments
 */
public class PluginFactory {

    /**
     * Extension point name for Plugin Access.
     */
    public static final String EXTENSION_POINT_NAME_PLUGIN = "org.eclipse.smila.search.plugin";

    /**
     * s_object.
     */
    private static Object s_object = new Object();

    /**
     * s_plugin.
     */
    private static Plugin s_plugin;

    /**
     * Constructor.
     */
    private PluginFactory() {

    }

    /**
     * @throws PluginException -
     */
    public static void initialize() throws PluginException {
        synchronized (s_object) {
            final String pluginName = null;
            try {
                EIFActivator.registerSchemas();
                // pluginName = ConfigManager
                // .getString(ConfigManager.AFSDK_PLUGIN);
                s_plugin = getInstance();
            } catch (final Throwable e) {
                throw new PluginException("unable to instanciate retrieval plugin [" + pluginName + "]", e);
            }
        }
    }

    public static Plugin getPlugin() {
        synchronized (s_object) {
            final Log log = LogFactory.getLog(PluginFactory.class);
            if (s_plugin == null) {
                try {
                    initialize();
                } catch (final PluginException exception) {
                    if (log.isErrorEnabled()) {
                        log.error(exception);
                    }
                }
            }

            return s_plugin;
        }
    }

    public static Plugin getInstance() {

        // TODO: implement correctly
        final Log log = LogFactory.getLog(PluginFactory.class);
        Plugin[] types;
        try {
            types = getTypes();
            if (types.length != 1) {
                if (log.isWarnEnabled()) {
                    log.warn("invalid plugin count [" + types.length + "]");
                }
                return null;
            }
            return types[0];
        } catch (final PluginException e) {
            if (log.isErrorEnabled()) {
                log.error(e);
            }
            return null;
        }
    }

    /**
     * Get all available IRM types.
     * 
     * @return IRM types.
     * @throws PluginException -
     */
    public static Plugin[] getTypes() throws PluginException {
        final Log log = LogFactory.getLog(PluginFactory.class);
        final List<Plugin> found = new ArrayList<Plugin>();
        // TODO: Check why the next line is needed.
        // found.add(UNKNOWN);
        final IExtension[] extensions = Platform.getExtensionRegistry()
                .getExtensionPoint(EXTENSION_POINT_NAME_PLUGIN).getExtensions();
        for (int i = 0; i < extensions.length; i++) {
            final IExtension extension = extensions[i];
            final IConfigurationElement[] configElements = extension.getConfigurationElements();

            for (int j = 0; j < configElements.length; j++) {
                final IConfigurationElement configurationElement = configElements[j];
                final String typeName = parseType(configurationElement, found.size());

                Plugin clazz = null;
                try {
                    final Object obj = configurationElement.createExecutableExtension("Clazz");
                    clazz = (Plugin) obj;
                } catch (final Exception exception) {
                    if (log.isErrorEnabled()) {
                        if (configurationElement != null) {
                            log.error("Failed to instantiate plugin");
                        } else {
                            log.error("Unknown!");
                        }
                    }
                    throw new PluginException("unable to load plugin", exception);
                }

                if (clazz != null) {
                    found.add(clazz);
                }
            }
        }

        return found.toArray(new Plugin[0]);
    }

    /**
     * Parse configuration and return according IRMType.
     * 
     * @param configurationElement
     *          Configuration element.
     * @param ordinal
     *          Ordinal.
     * @return Type name.
     */
    public static String parseType(IConfigurationElement configurationElement, int ordinal) {

        final Log log = LogFactory.getLog(PluginFactory.class);

        if (!configurationElement.getName().equals("Plugin")) {
            return null;
        }

        try {
            String name = configurationElement.getAttribute("Clazz");
            if (name == null) {
                name = "[missing attribute name]";
            }
            return name;
        } catch (final Exception e) {
            if (log.isErrorEnabled()) {
                String name = configurationElement.getAttribute("Clazz");
                if (name == null) {
                    name = "[missing attribute name]";
                }
                final String msg = "Failed to load plugin named " + name + " in "
                        + configurationElement.getDeclaringExtension().getNamespaceIdentifier();
                log.error(msg, e);
            }
            return null;
        }
    }

}