org.eclipse.smila.search.datadictionary.DataDictionaryAccess.java Source code

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Here is the source code for org.eclipse.smila.search.datadictionary.DataDictionaryAccess.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: brox IT-Solutions GmbH - initial creator
 **********************************************************************************************************************/

package org.eclipse.smila.search.datadictionary;

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.datadictionary.messages.datadictionary.DConnection;
import org.eclipse.smila.search.datadictionary.messages.datadictionary.DDException;
import org.w3c.dom.Element;

/**
 * @author brox IT-Solutions GmbH
 */
public abstract class DataDictionaryAccess {

    /**
     * Extension point name for Data Dictionary Accesss.
     */
    public static final String EXTENSION_POINT_NAME_DATA_DICTIONARY_ACCESS = "org.eclipse.smila.search.datadictionary.access";

    /**
     * Cached Data Dictionary Access types.
     */
    private static DataDictionaryAccess[] s_cachedDataDictionaryAccess;

    /**
     * DataDicitonaryAccess.
     * 
     * @return - an access object.
     */
    public static DataDictionaryAccess getInstance() {

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

        DataDictionaryAccess[] types;
        try {
            types = getTypes();
            if (types.length != 1) {
                if (log.isWarnEnabled()) {
                    log.warn("invalid data dictionary access count [" + types.length + "]");
                }
                return null;
            }
            return types[0];
        } catch (final DataDictionaryException e) {
            if (log.isErrorEnabled()) {
                log.error(e);
            }
            return null;
        }
    }

    /**
     * Get all available IRM types.
     * 
     * @return IRM types.
     * @throws DataDictionaryException
     *           DataDictionaryException.
     */
    public static DataDictionaryAccess[] getTypes() throws DataDictionaryException {

        if (s_cachedDataDictionaryAccess != null) {
            return s_cachedDataDictionaryAccess;
        }

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

        final List<DataDictionaryAccess> found = new ArrayList<DataDictionaryAccess>();
        // TODO: Check why the next line is needed.
        // found.add(UNKNOWN);
        final IExtension[] extensions = Platform.getExtensionRegistry()
                .getExtensionPoint(EXTENSION_POINT_NAME_DATA_DICTIONARY_ACCESS).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];
                DataDictionaryAccess clazz = null;
                try {
                    final Object obj = configurationElement.createExecutableExtension("Clazz");
                    clazz = (DataDictionaryAccess) obj;
                } catch (final Exception exception) {
                    if (log.isErrorEnabled()) {
                        if (configurationElement != null) {
                            log.error("Failed to instantiate data dictionary access");
                        } else {
                            log.error("Unknown!");
                        }
                    }
                    throw new DataDictionaryException("unable to load data dictionary access", exception);
                }

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

        s_cachedDataDictionaryAccess = found.toArray(new DataDictionaryAccess[0]);
        return s_cachedDataDictionaryAccess;
    }

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

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

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

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

    /**
     * Constructor.
     */
    public DataDictionaryAccess() {
    }

    /**
     * Connection object.
     * 
     * @param eConnection -
     *          element connection.
     * @return - DConnection object.
     * @throws DDException -
     *           a possible exception.
     */
    public abstract DConnection decodeConnection(Element eConnection) throws DDException;

    /**
     * @param dConnection -
     *          dConnection object.
     * @param element -
     *          a connection element.
     * @return - the element.
     * @throws DDException -
     *           a exception.
     */
    public abstract Element encodeConnection(DConnection dConnection, Element element) throws DDException;
}