//$Id: Implementation.java,v 1.3.2.1 2003/11/26 16:08:17 oneovthafew Exp $package net.sf.hibernate.odmg;import java.util.ArrayList;import java.util.HashMap;import java.util.HashSet;import org.odmg.DArray;import org.odmg.DBag;import org.odmg.DList;import org.odmg.DMap;import org.odmg.DSet;import org.odmg.ODMGException;import org.odmg.ODMGRuntimeException;import net.sf.hibernate.HibernateException;import net.sf.hibernate.collection.Bag;import net.sf.hibernate.collection.List;import net.sf.hibernate.collection.Map;import net.sf.hibernate.collection.Set;import net.sf.hibernate.engine.SessionImplementor;/** * Singleton class implementing the ODMG <tt>Implementation</tt> interface. * Maintains a reference to a default <tt>Database</tt> and also associations * between a <tt>Database</tt> and the creating <tt>Thread</tt>. */public class Implementation implements org.odmg.Implementation {		private Database database;	private final ThreadLocal threadDatabase = new ThreadLocal();	private static final Implementation INSTANCE = new Implementation();		/**	 * Get the singleton instance	 */	public static Implementation getInstance() {		return INSTANCE;	}	/**	 * Instantiate a new <tt>Transaction</tt> associated with the current	 * thread.	 * @see org.odmg.Implementation#newTransaction()	 */	public org.odmg.Transaction newTransaction() {		try {			return new Transaction( currentDatabase() );		}		catch (ODMGException ode) {			throw new ODMGRuntimeException( ode.getMessage() );		}	}		/**	 * Get the <tt>Database</tt> associated with the current thread (the most recent	 * database created by the current thread or the default database).	 */	public Database currentDatabase() {		Database db = (Database) threadDatabase.get();		if (db!=null) {			return db;		}		else {			return database;		}	}	/**	 * Get the <tt>Transaction</tt> associated with the current thread.	 * @see org.odmg.Implementation#currentTransaction()	 */	public org.odmg.Transaction currentTransaction() {		return currentDatabase().currentTransaction();	}	/**	 * Create a new <tt>Database</tt> and associate it with the current thread.	 * The first <tt>Database</tt> created by this method becomes the "default"	 * database that all threads that have not created databases are associated	 * with.	 * @see org.odmg.Implementation#newDatabase()	 */	public synchronized org.odmg.Database newDatabase() {		Database db = new Database();		if (database==null) database=db;		threadDatabase.set(db);		return db;	}	/**	 * Instantiate an <tt>OQLQuery</tt> for the <tt>Database</tt> associated with	 * the current thread	 * @see org.odmg.Implementation#newOQLQuery()	 */	public org.odmg.OQLQuery newOQLQuery() {		return new OQLQuery( currentDatabase() );	}	/**	 * @see org.odmg.Implementation#newDList()	 */	public DList newDList() {		return new List( (SessionImplementor) currentDatabase().getSession(), new ArrayList() );	}	/**	 * @see org.odmg.Implementation#newDBag()	 */	public DBag newDBag() {		return new Bag( (SessionImplementor) currentDatabase().getSession(), new ArrayList() );	}	/**	 * @see org.odmg.Implementation#newDSet()	 */	public DSet newDSet() {		return new Set( (SessionImplementor) currentDatabase().getSession(), new HashSet() );	}	/**	 * @see org.odmg.Implementation#newDArray()	 */	public DArray newDArray() {		return new List( (SessionImplementor) currentDatabase().getSession(), new ArrayList() );	}	/**	 * @see org.odmg.Implementation#newDMap()	 */	public DMap newDMap() {		return new Map( (SessionImplementor) currentDatabase().getSession(), new HashMap() );	}	/**	 * Get the stringified identifier of the given object.	 * @see org.odmg.Implementation#getObjectId(Object)	 */	public String getObjectId(Object obj) {		try {			return database.getSession().getIdentifier(obj).toString();		}		catch (HibernateException he) {			throw new ODMGRuntimeException( he.getMessage() );		}	}	/**	 * Get the <tt>Database</tt> associated with the current thread (the most recent	 * database created by the current thread or the default database).	 * @see org.odmg.Implementation#getDatabase(Object)	 */	public org.odmg.Database getDatabase(Object obj) {		//TODO: improve this		return currentDatabase();	}	}