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The Jadex nuggets is a fast Java bean to XML and back converter.
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/*
 * BeanAssembler.java Copyright (c) 2005 by University of Hamburg. All Rights
 * Reserved. Departament of Informatics. Distributed Systems and Information
 * Systems. Created by walczak on Jan 16, 2006. Last revision $Revision: 6926 $
 * by: $Author: braubach $ on $Date: 2008-09-28 22:16:58 +0200 (So, 28 Sep 2008)
 * $.
 */
package nuggets;

import java.io.Reader;
import java.util.ArrayList;
import java.util.Arrays;

import nuggets.IReader.Buffer;


/**
 * BeanAssembler
 * 
 * @author walczak
 * @since Jan 16, 2006
 */
public class BeanAssembler implements IAssembler
{
	private static final int	OBJECT_ARRAY_LENGTH	= 512;

	private Object[]			objects				= new Object[OBJECT_ARRAY_LENGTH];

	private final ArrayList		delayed				= new ArrayList();

	private IReader				reader;

	private String				pack;

	/**
	 * @param reader
	 */
	public void setReader(IReader reader)
	{
		this.reader = reader;
	}

	/**
	 * @param rdr
	 * @return the object with id == 0
	 */
	public Object assemble(Reader rdr, ClassLoader classloader)
	{
		try
		{
			clear();
			parse(rdr, classloader);
			perform_delayed();
		}
		catch(Exception e)
		{
			e.printStackTrace();
			throw new PersistenceException(e);
		}

		return get(1);
	}

	/**
	 * remove all chached objects from this one
	 */
	public void clear()
	{
		delayed.clear();
		Arrays.fill(objects, null);
	}

	// ------------ IAssembler -----------------

	/**
	 * @param attribute
	 * @return the value of the attribute including null if not available yet
	 */
	public Object getAttributeValue(String attribute)
	{
		int i = reader.getAttributeIndex(attribute);
		if(i < 0)
			return null;
		if(!reader.isReferenceAttribute(i))
			return reader.getAttributeValue(i);

		String str_id = reader.getAttributeValue(i);

		int id = Integer.parseInt(str_id, 16);
		if(has(id))
			return get(id);
		// else
		delay(new AttributeSetOperation(delegate, object, attribute, str_id));
		return null;
	}

	/** buffer for reader text */
	protected Buffer	buffer;

	/** the offset of next token - space separated */
	protected int		token_offset;

	private IDelegate	delegate;

	private Object		object;

	/**
	 * @return the text of an element
	 * @see nuggets.IAssembler#getText()
	 */
	public String getText()
	{
		if(buffer == null)
		{
			buffer = reader.getText();
			if(buffer == null)
				return null; // no more tokens from reader for
		}
		return reader.decodeText(buffer.chars, buffer.start, buffer.len);
	}

	/**
	 * @return return the byte array from the text data
	 * @see nuggets.IAssembler#getData()
	 */
	public byte[] getData()
	{
		return reader.getData();
	}

	/**
	 * It assumes that there is only one text content per element
	 * 
	 * @return the next token from character stream
	 * @see nuggets.IAssembler#nextToken()
	 */
	public String nextToken()
	{
		if(buffer == null)
		{
			buffer = reader.getText();
			if(buffer == null)
				return null; // no more tokens from reader for
			// this element
			token_offset = buffer.start;
		}

		int end = buffer.start + buffer.len;
		for(int i = token_offset; i < end; i++)
		{
			char c = buffer.chars[i];
			if(c == ' ')
			{
				if(i > token_offset)
				{
					String ret = new String(buffer.chars, token_offset, i
							- token_offset);
					token_offset = i + 1;
					return ret;
				}
				token_offset = i + 1;
			}
		}
		if(end > token_offset)
		{
			String ret = new String(buffer.chars, token_offset, end
					- token_offset);
			token_offset = end;
			return ret;
		}
		return null;
	}

	/**
	 * @param sid
	 * @return the object with id
	 * @throws InstanceNotAvailableException
	 */
	public Object getValue(String sid) throws InstanceNotAvailableException
	{
		try
		{
			int id = Integer.parseInt(sid, 16);
			if(id == 0)
				return null;
			Object ret = objects[id];
			if(ret == null)
			{
				throw new InstanceNotAvailableException(sid);
			}
			return ret;
		}
		catch(NumberFormatException nfe)
		{
			throw new PersistenceException(nfe);
		}
	}

	/**
	 * @param op
	 * @see nuggets.IAssembler#delay(nuggets.IDelayedOperation)
	 */
	public void delay(IDelayedOperation op)
	{
		delayed.add(op);
	}

	/**
	 * @return the reader used to read the document
	 * @see nuggets.IAssembler#getReader()
	 */
	public IReader getReader()
	{
		return reader;
	}

	// ----------------------------------------------------------------

	/**
	 * @param id
	 * @return tests if the object with this id is read
	 */
	private boolean has(int id)
	{
		return id == 0 || id < objects.length && objects[id] != null;
	}

	/**
	 * @param id
	 * @return tests if the object with this id is read
	 */
	private Object get(int id)
	{
		return id < objects.length ? objects[id] : null;
	}

	/**
	 * @param rdr
	 * @throws Exception
	 */
	private void parse(Reader rdr, ClassLoader classloader) throws Exception
	{
		reader.start(rdr);
		this.pack = reader.getAttributeValue("xmlns");

		String tag;
		while((tag = reader.nextElement()) != null)
		{
			buffer = null;
			int id = Integer.parseInt(reader.getID(), 16);
			Class clazz = getClass(tag, classloader);
			delegate = PersistenceHelper.getDelegate(clazz, classloader);
			object = delegate.getInstance(clazz, this);
			set(id, object);
			delegate.assemble(object, this);
		}
	}

	/**
	 * @param id
	 * @param obj
	 */
	private void set(int id, Object obj)
	{
		if(objects.length <= id)
		{
			Object[] tmp = new Object[Math.max(id + 64, objects.length << 1)];
			System.arraycopy(objects, 0, tmp, 0, objects.length);
			objects = tmp;
		}
		objects[id] = obj;
	}

	/**
	 * performs all delayed operations
	 */
	private void perform_delayed()
	{
		int len = delayed.size();
		for(int i = 0; i < len; i++)
		{
			IDelayedOperation l = (IDelayedOperation)delayed.get(i);
			try
			{
				l.perform(this);
			}
			catch(Exception e)
			{
				e.printStackTrace();
			}
		}
		delayed.clear();
	}

	/**
	 * @param tag
	 * @return the class for this tag
	 * 
	 * Java Bug with classloader.loadClass() fails in JDK6 for array types.
	 * http://bugs.sun.com/bugdatabase/view_bug.do;jsessionid=8ba64503affecffffffffb6789c3d861677d?bug_id=6434149
	 */
	private Class getClass(String tag, ClassLoader classloader)
	{
		// In case no classloader is set use current or context classloader?
		if(classloader==null)
		{
//			classloader = BeanAssembler.class.getClassLoader();
			classloader = Thread.currentThread().getContextClassLoader();
		}
		
		if(tag.startsWith("array"))
		{
			tag = reader.getAttributeValue("type");
		}
		try
		{
			if(pack != null)// && tag.indexOf('.') < 0)
				return Class.forName(pack + '.' + tag, true, classloader);
//				return classloader.loadClass(pack + '.' + tag); 
		}
		catch(ClassNotFoundException e1)
		{ 
			/* NOP */
		}
		try
		{
			return Class.forName(tag, true, classloader);
//			return classloader.loadClass(tag); 
		}
		catch(ClassNotFoundException e)
		{
			throw new PersistenceException(e);
		}
	}
}