kalumet-modules/common/src/main/java/org/apache/kalumet/model/log/Journal.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.kalumet.model.log;

import org.apache.commons.digester.Digester;
import org.apache.kalumet.KalumetException;
import org.apache.xerces.dom.CoreDocumentImpl;
import org.apache.xerces.dom.ElementImpl;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;
import org.w3c.dom.Element;

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * Manages the environment log file and represents the <code>journal</code>
 * root tag.
 */
public class Journal
{

    private LinkedList events;

    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

    public Journal()
    {
        this.events = new LinkedList();
    }

    /**
     * Adds a new <code>Event</code> in the <code>Journal</code> container.
     *
     * @param event the <code>Event</code> to add.
     */
    public void addEvent( Event event )
    {
        this.events.add( event );
    }

    /**
     * Gets the <code>Event</code> list in the <code>Journal</code>
     * container.
     *
     * @return the <code>Event</code> list.
     */
    public List getEvents()
    {
        return this.events;
    }

    /**
     * Transforms the <code>Journal</code> POJO to a DOM element.
     *
     * @param document the DOM document.
     * @return the DOM element.
     */
    protected Element toDOMElement( CoreDocumentImpl document )
    {
        ElementImpl element = new ElementImpl( document, "journal" );
        // events
        for ( Iterator eventIterator = this.getEvents().iterator(); eventIterator.hasNext(); )
        {
            Event event = (Event) eventIterator.next();
            element.appendChild( event.toDOMElement( document ) );
        }
        return element;
    }

    /**
     * Parses and loads a given XML log file and return the environment journal root tag.
     *
     * @param path the environment log XML to parse.
     * @return the environment <code>Journal</code> corresponding with the journal root tag.
     */
    public static Journal digeste( String path )
        throws KalumetException
    {
        if ( !path.startsWith( "http:" ) && !path.startsWith( "HTTP:" ) && !path.startsWith( "file:" )
            && !path.startsWith( "FILE:" ) )
        {
            path = "file:" + path;
        }
        Journal journal = null;
        try
        {

            // init the digester with no validation on the XML file (no DTD)
            Digester digester = new Digester();
            digester.setValidating( false );

            // journal tag rules
            digester.addObjectCreate( "journal", "org.apache.kalumet.model.log.Journal" );
            digester.addSetProperties( "journal" );

            // event tag rules
            digester.addObjectCreate( "journal/event", "org.apache.kalumet.model.log.Event" );
            digester.addSetProperties( "journal/event" );

            // event content
            digester.addCallMethod( "journal/event", "setContent", 0 );

            // add event to journal
            digester.addSetNext( "journal/event", "addEvent", "org.apache.kalumet.model.log.Event" );

            // parse the XML file
            journal = (Journal) digester.parse( path );
        }
        catch ( IOException ioException )
        {
            // most of the time IOException occurs because the journal file path
            // doesn't exist, try to create it
            journal = new Journal();
            journal.writeXMLFile( path );
        }
        catch ( Exception e )
        {
            throw new KalumetException( "Can't read journal", e );
        }
        return journal;
    }

    /**
     * Writes the environment journal log XML file with the in-memory DOM.
     *
     * @param path the path to the file to write.
     */
    public void writeXMLFile( String path )
        throws KalumetException
    {
        try
        {
            lock.writeLock().lock();
            OutputFormat format = new OutputFormat();
            format.setLineWidth( 72 );
            format.setIndenting( true );
            format.setIndent( 3 );
            format.setEncoding( "ISO-8859-1" );
            if ( path.startsWith( "http:" ) || path.startsWith( "http:" ) )
            {
                throw new KalumetException( "Can't write journal file over a HTTP URL" );
            }
            if ( path.startsWith( "file:" ) || path.startsWith( "FILE:" ) )
            {
                path = path.substring( 5 );
            }
            XMLSerializer serializer = new XMLSerializer( new FileOutputStream( path ), format );
            serializer.serialize( this.toDOMElement( new CoreDocumentImpl( true ) ) );
        }
        catch ( Exception e )
        {
            throw new KalumetException( "Can't write journal", e );
        }
        finally
        {
            lock.writeLock().unlock();
        }
    }

}