encodertemplate.java

Java Communicating Agents是一个用于开发网络反应式信息agent的框架

/*
 * $Source: /home/data/cvsroot/src/jacomma/icm/io/imp/EncoderTemplate.java,v $
 * $Revision: 1.9 $
 * $Date: 2000/10/28 20:09:07 $
 *
 * This file is part of the jacomma framework
 * Copyright (c) 2000 	Dimitrios Vyzovitis
 *			mailto:[e-mail]
 *			
 *
 *			
 *			
 *			
 *
 *	This library is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU Library General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *
 *	This library 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 Library General Public License for more details.
 *
 *	You should have received a copy of the GNU Library General Public License
 *	along with this library; if not, write to the Free Software
 *	Foundation, Inc., 59 Temple Place, Suite 330, 
 *	Boston, MA  02111-1307  USA
 */

package jacomma.icm.io.imp;

import jacomma.icm.io.EncObject;
import jacomma.icm.io.EncObjectType;
import jacomma.icm.io.EncObjectSignature;
import jacomma.icm.io.ObjectEncoder;

import jacomma.util.Cache;

import java.util.Iterator;
import java.util.Set;

/**
 * TBA
 **/
public abstract class EncoderTemplate implements ObjectEncoder {

	protected Set all_ = new java.util.HashSet( 4 );
	protected Set some_ = new java.util.HashSet( 4 );
	protected boolean sign_ = false; // default behavior for signatures
	protected Cache cache_ = new Cache();

	protected EncoderTemplate(){}

	public EncObject encode( Object obj ) {
		return encode( obj, null, sign_ );
	}

	public EncObject encode( Object obj, boolean sign ) {
		return encode( obj, null, sign );
	}

	public EncObject encode( Object obj, Object hint ) {
		return encode( obj, hint, sign_ );
	}
	
	protected EncObject sign( String s, EncObject obj ) {
		CacheKey key = new CacheKey( obj, s, true );
		EncObject sobj = (EncObject)cache_.get( key );
		if ( sobj == null ) {
			obj.setSignature( s );
			sobj = (EncObject)cache_.try_put( key, Registry.instance.getEncoder( obj ).encode( obj ) );
		}
		
		return sobj;
	}

	protected EncObject sign( EncObject obj ) {
		return sign( EncObjectSignature.signatureOf( obj ), obj );
	}

	public boolean canHandle( Object obj ) {
		return canHandle( obj.getClass() );
	}

	public boolean canHandleSome( Class c ) {
		return check( c, some_ );
	}

	public boolean canHandle( Class c ) {
		return check( c, all_ );
	}

	
	protected boolean check( Class c, Set set ) {
		boolean r;
		if ( !(r = set.contains( c )) )
			// ok, let's check whether it is a sub-class
			for ( Iterator it = set.iterator();
				  !r && it.hasNext();
				  r = ((Class)it.next()).isInstance( c ) );
		
		return r;
	}


	// utility class for creating cache keys for Objects to be encoded
	// Note that signed objects are stored using a different key to avoid
	// confusion (that key is the object itself).
	protected class CacheKey {
		Object obj_;
		Object hint_;
		boolean sig_;

		public CacheKey( Object obj, Object hint, boolean sig ) {
			obj_ = obj;
			hint_ = hint;
			sig_ = sig;
		}

		public CacheKey( Object obj,  boolean sig ) {
			obj_ = obj;
			sig_ = sig;
		}
		
		public CacheKey( Object obj, Object hint ) {
			obj_ = obj;
			hint_ = hint;
		}
		
		public CacheKey( Object obj ) {
			obj_ = obj;
		}
		
		public int hashCode() {
			return obj_.hashCode();
		}
		
		public boolean equals( Object obj ) {
			try {
				return obj_.equals( ((CacheKey)obj).obj_ )
					&& ( (hint_ == null) ? 
						 (((CacheKey)obj).hint_ == null) : 
						 hint_.equals( ((CacheKey)obj).hint_ ) )
					&& sig_ == ((CacheKey)obj).sig_;
			} catch ( ClassCastException exc ) {
				return false;
			}
		}

	}
}