dbmodtimes.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Core License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: DbModTimes.java,v 1.4 2000/10/28 16:55:17 daniela Exp $

package org.ozoneDB.core.DbRemote;

import java.io.*;
import org.ozoneDB.DxLib.*;
import org.ozoneDB.*;
import org.ozoneDB.core.*;
import org.ozoneDB.util.*;


/**
 * Determine the modification times of the specified database objects.
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.4 $Date: 2000/10/28 16:55:17 $
 */
public final class DbModTimes extends DbCommand implements Externalizable {
    
    private DxArrayBag objectIDs;
    
    
    public DbModTimes() {
        objectIDs = new DxArrayBag();
    }
    
    
    public void addObjectID( ObjectID id ) {
        objectIDs.add( id );
    } 
    
    
    public void perform( Transaction ta ) throws Exception {
        env.logWriter.newEntry( this, "DbModTimes.perform()", LogWriter.DEBUG );
        
        // check (and wait) if a thread runs exclusively; because no
        // transaction is involved we have to do this here
        env.transactionManager.checkExclusion();
        
        DxMap map = new DxHashMap( objectIDs.count() );
        for (int i = 0; i < objectIDs.count(); i++) {
            ObjectID id = (ObjectID)objectIDs.elementAtIndex( i );
            
            env.logWriter.newEntry( this, "    id:" + id, LogWriter.DEBUG );
            
            ObjectContainer container = env.store.containerForID( ta, id );
            if (container == null) {
                throw new ObjectNotFoundExc( "No such object." );
            } 
            
            Long modTime = new Long( container.modTime() );
            
            map.addForKey( modTime, id );
        } 
        
        result = map;
    } 
    
    
    public void writeExternal( ObjectOutput out ) throws IOException {
        out.writeObject( objectIDs );
    } 
    
    
    public synchronized void readExternal( ObjectInput in ) throws IOException, ClassNotFoundException {
        objectIDs = (DxArrayBag)in.readObject();
    } 
    
}