XMLFileSettingsLoader.java

/*
 * #%L
 * Bitrepository Protocol
 * 
 * $Id$
 * $HeadURL$
 * %%
 * Copyright (C) 2010 - 2011 The State and University Library, The Royal Library and The State Archives, Denmark
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as 
 * published by the Free Software Foundation, either version 2.1 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 Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public 
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */
package org.bitrepository.common.settings;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

import org.bitrepository.common.JaxbHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.SAXException;

/**
 * Loads settings as xml from the classpath.
 *
 */
public class XMLFileSettingsLoader implements SettingsLoader {
    /** The log for this class. */
    private final Logger log = LoggerFactory.getLogger(getClass());

    private String pathToSettingsFiles;

    /** Directory seperator constant */
    private static final String DIRECTORY_SEPERATOR = "/";
    /** xml file extension constant */
    private static final String XML_FILE_EXTENSION = ".xml";
    /** xsd file extension constant */
    private static final String XSD_FILE_EXTENSION = ".xsd";
    /** xsd schema directory constant */
    private static final String XSD_SCHEMA_DIR = "xsd/";

    /**
     * Creates a new loader
     * @param pathToSettingsFiles The location of the files to load. The settings xml files are assume to be placed as
     * ${CONFIGURATION_CLASS}.xml under this directory.
     *
     */
    public XMLFileSettingsLoader(String pathToSettingsFiles) {
        this.pathToSettingsFiles = pathToSettingsFiles;
    }

    /**
     * Loads the indicated settings for the specified collection.
     * @param settingsClass The settings class identifying the type of settings requested.
     * @param <T> The type of settings to return
     * @return The loaded settings.
     */
    public <T> T loadSettings(Class<T> settingsClass) {
        StringBuilder fileLocationBuilder = new StringBuilder();
        if (pathToSettingsFiles != null && !pathToSettingsFiles.equals("")) {
            fileLocationBuilder.append(pathToSettingsFiles).append(DIRECTORY_SEPERATOR);
        }
        fileLocationBuilder.append(settingsClass.getSimpleName()).append(XML_FILE_EXTENSION);
        String fileLocation = fileLocationBuilder.toString();
        String schemaLocation = settingsClass.getSimpleName() + XSD_FILE_EXTENSION;
        JaxbHelper jaxbHelper = new JaxbHelper(XSD_SCHEMA_DIR, schemaLocation);
        InputStream configStreamLoad = null;
        InputStream configStreamValidate = null;
        try {
            configStreamLoad = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileLocation);
            configStreamValidate = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileLocation);
            if (configStreamLoad == null) {
                try {
                    configStreamLoad = new FileInputStream(fileLocation);
                    configStreamValidate = new FileInputStream(fileLocation);
                } catch (FileNotFoundException e) {
                    throw new RuntimeException("Unable to load settings from " + fileLocation, e);
                }
            }
            log.debug("Loading the settings file '" + fileLocation + "'.");
            try {
                jaxbHelper.validate(configStreamValidate);
                return jaxbHelper.loadXml(settingsClass, configStreamLoad);
            } catch (SAXException e) {
                throw new RuntimeException("Unable to validate settings from " +
                        Thread.currentThread().getContextClassLoader().getResource(fileLocation), e);
            } catch (Exception e) {
                throw new RuntimeException("Unable to load settings from " + fileLocation, e);
            }
        } finally {
            try {
                if (configStreamLoad != null) configStreamLoad.close();
                if (configStreamValidate != null) configStreamValidate.close();
            } catch (IOException e) {
                throw new RuntimeException("Unable to close inputstream", e);
            }
        }
    }
}