jfix.db4o.engine.PersistenceEngineXStream.java Source code

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Here is the source code for jfix.db4o.engine.PersistenceEngineXStream.java

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/*
Copyright (C) 2016 maik.jablonski@jease.org
    
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 3 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, see <http://www.gnu.org/licenses/>.
 */
package jfix.db4o.engine;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.io.FileUtils;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

/**
 * This implemenation is ONLY intended for debug-purposes.
 * 
 * @author mjablonski
 */
public class PersistenceEngineXStream implements PersistenceEngine {

    protected String directory;
    protected String filename;
    protected Set<Object> objects;
    protected Set<Object> objectsToSave;
    protected Set<Object> objectsToDelete;

    public void open(String database) {
        initDirectory(database);
        openEngine();
    }

    protected void initDirectory(String database) {
        if (database.contains(File.separator)) {
            directory = database.endsWith(File.separator) ? database : database + File.separator;
        } else {
            directory = System.getProperty("user.home") + File.separator + "xstream" + File.separator + database
                    + File.separator;
        }
        filename = directory + "odb.xml";
        new File(directory).mkdirs();
    }

    protected void openEngine() {
        objects = new HashSet<>();
        objectsToSave = new HashSet<>();
        objectsToDelete = new HashSet<>();
    }

    public String getBlobDirectory() {
        return directory;
    }

    public Collection<Object> query() {
        try {
            if (new File(filename).exists()) {
                XStream xstream = new XStream(new DomDriver());
                xstream.setMode(XStream.ID_REFERENCES);
                FileReader reader = new FileReader(filename);
                objects = (Set<Object>) xstream.fromXML(reader);
                reader.close();
            }
            return objects;
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    public void save(Object object) {
        objectsToSave.add(object);
    }

    public void delete(Object object) {
        objectsToDelete.add(object);
    }

    public void begin() {
        // Empty as XStream has no concept of transactions at all.
    }

    public void commit() {
        objects.addAll(objectsToSave);
        objects.removeAll(objectsToDelete);
        objectsToSave.clear();
        objectsToDelete.clear();
    }

    public void rollback() {
        objectsToSave.clear();
        objectsToDelete.clear();
    }

    public void backup() {
        try {
            String backupFilename = filename + new SimpleDateFormat("-yyyyMMdd").format(new Date());
            FileUtils.copyFile(new File(filename), new File(backupFilename));
        } catch (IOException e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    public void close() {
        try {
            XStream xstream = new XStream(new DomDriver());
            xstream.setMode(XStream.ID_REFERENCES);
            FileWriter writer = new FileWriter(filename);
            xstream.toXML(objects, writer);
            writer.close();
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage(), e);
        }
    }

    public String toString() {
        return filename;
    }
}