attachmentbean.java

老外的在线考试

/*
 * SchoolEJB - CyberDemia's library of EJBs for educational related services.
 * Copyright (C) 2003 CyberDemia Research and Services
 *
 * 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.
 *
 * See the COPYING file located in the top-level-directory of
 * the archive of this library for complete text of license.
 */
package com.cyberdemia.school;

import javax.ejb.*;
import com.cyberdemia.ejb.BaseEntityBean;

/**
 * <p>
 * AttachmentBean stores the data and meta-data for attachments to questions/answer choices/etc,
 * such as GIF/PNG images. The object that it is attached to is referred to as the "owner",
 * and its ID is stored as the ownerId field. The owner type is stored as the ownerType field. 
 * </p>
 * <p>
 * Container-managed-relationship is not used to associate AttachmentBean to its owner
 * because it may be very expensive and wasteful to always retrieve attachment content
 * whenever the owner is accessed. Therefore, this relationship is managed by application code.
 * Attachment data is only accessed when required.
 * </p>
 * 
 * @ejb.bean name="AttachmentBean"
 *           type="CMP"
 *           view-type="local"
 *           schema="Attachment"
 *           cmp-version="2.x"
 *           primkey-field="id"
 *           local-jndi-name="ejb/LocalAttachment"
 *
 * @ejb.util generate="physical"
 * @ejb.interface local-class="com.cyberdemia.school.LocalAttachment" local-extends="javax.ejb.EJBLocalObject"
 * @ejb.home local-class="com.cyberdemia.school.LocalAttachmentHome" local-extends="javax.ejb.EJBLocalHome"
 * @ejb.pk class="java.lang.Integer"
 * @ejb.persistence table-name="CDAttachment"
 *
 * @ejb.finder signature="java.util.Collection findByOwner(java.lang.Integer ownerId, java.lang.Integer ownerType)"
 *             query="SELECT DISTINCT OBJECT(a) FROM Attachment a WHERE a.ownerId=?1 AND a.ownerType=?2"
 * @jboss.query signature="java.util.Collection findByOwner(java.lang.Integer ownerId, java.lang.Integer ownerType)"
 *             query="SELECT DISTINCT OBJECT(a) FROM Attachment a WHERE a.ownerId=?1 AND a.ownerType=?2 ORDER BY a.orderingIndex"
 *
 * @jboss.method-attributes pattern="get*" read-only="true"
 *
 * @jboss.unknown-pk class="java.lang.Integer" auto-increment="true" jdbc-type="INTEGER" sql-type="INTEGER"
 * @jboss.entity-command name="mysql-get-generated-keys"
 * @jboss.container-configuration name="CyberDemia Optimized Standalone CMP"
 *
 * @author Alexander Yap
 * @version $Revision: 1.1 $ at $Date: 2004/06/20 14:56:19 $ by $Author: alexycyap $
 */
public abstract class AttachmentBean extends BaseEntityBean
{
	/**
	* Value of ownerType field to denote that the owner is a Question.
	*/
	public static final Integer QUESTION_OWNER_TYPE = new Integer(0);
	
	/**
	* Value of ownerType field to denote that the owner is an AnswerChoice.
	*/
	public static final Integer ANSWER_CHOICE_OWNER_TYPE = new Integer(1);

	
	/**
	 * Gets the ID (primary key) of this answer choice.
	 *
	 * @ejb.persistence
	 * @ejb.pk-field
	 * @ejb.interface-method
	 * @jboss.persistence auto-increment="true"
	 *
	 * @return ID of this answer choice.
	 */
	public abstract Integer getId();

	/**
	 * Sets the ID (primary key) of this answer choice.
	 * @param id ID of this answer choice.
	 */
	public abstract void setId(Integer id);
	
	/**
	* Gets the attachment content.
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.jdbc-type type="BLOB"
	* @jboss.sql-type type="MEDIUMBLOB"
	*
	* @return Attachment content
	*/
	public abstract byte[] getContent();

	public abstract void setContent(byte[] content);

	/**
	* Gets the attachment content type.
	* For example "image/gif".
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true"
	*
	* @return Attachment content type
	*/
	public abstract String getContentType();

	/**
	* Sets the attachment content type.
	* For example "image/gif".
	*
	* @param contentType Attachment content type
	*/
	public abstract void setContentType(String contentType);

	/**
	* Gets the attachment content size in bytes.
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true"
	*
	* @return Attachment content size in bytes
	*/
	public abstract long getSize();

	/**
	* Sets the attachment content size in bytes.
	*
	* @param size Attachment content size in bytes
	*/
	public abstract void setSize(long size);

	/**
	* Gets the attachment ordering index.
	* This is used to preserve the ordering of multiple attachments to a owner.
	* The first attachment has index 0, second attachment has index 1, etc.
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true"
	*
	* @return Ordering index
	*/
	public abstract int getOrderingIndex();

	/**
	* Sets the attachment ordering index.
	* This is used to preserve the ordering of multiple attachments to a owner.
	*
	* @param index Ordering index
	*/
	public abstract void setOrderingIndex(int index);

	/**
	* Gets the attachment positioning meta-data.
	* This is useful when the attachment may be laid out visually on the GUI.
	* For example a GIF image attached to a question may have position
	* specified as "EAST" to indicate that it should be displayed to the right
	* of the main question text.
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true"
	*
	* @return Positioning meta data.
	*/
	public abstract String getPosition();

	/**
	* Sets the attachment positioning meta-data.
	* This is useful when the attachment may be laid out visually on the GUI.
	* For example a GIF image attached to a question may have position
	* specified as "EAST" to indicate that it should be displayed to the right
	* of the main question text.
	*
	* @ejb.interface-method
	*
	* @param position Positioning meta data
	*/
	public abstract void setPosition(String position);

	/**
	* Gets the owner ID.
	* This is the ID of the object that this attachment is attached to.
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true" dbindex="true"
	*
	* @return Owner ID.
	*/
	public abstract Integer getOwnerId();

	/**
	* Sets the owner ID.
	* This is the ID of the object that this attachment is attached to.
	*
	* @param ownerId Owner ID
	*/
	public abstract void setOwnerId(Integer ownerId);

	/**
	* Gets the owner type.
	* For example AttachmentBean.QUESTION_OWNER_TYPE or AttachmentBean.ANSWER_CHOICE_OWNER_TYPE. 
	*
	* @ejb.interface-method
	* @ejb.persistence
	* @jboss.persistence not-null="true" dbindex="true"
	*
	* @return Owner type.
	*/
	public abstract Integer getOwnerType();

	/**
	* Sets the owner type.
	* For example AttachmentBean.QUESTION_OWNER_TYPE or AttachmentBean.ANSWER_CHOICE_OWNER_TYPE. 
	*
	* @param ownerType Owner type
	*/
	public abstract void setOwnerType(Integer ownerType);

	
	/**
	* Gets the auto-generated primary key (field "id").
	* Useful to retrieve the primary key immediately after
	* creating the bean, when <code>getId()</code> would return null.
	* This method will convert the primary key to an Integer,
	* which is the type of the "id" field.
	*
	* @ejb.interface-method
	*
	* @return Primary key
	*/
	public Integer getGeneratedPrimaryKey()
	{
		Object pk = getEntityContext().getPrimaryKey();
		if (pk instanceof Integer)
		{
			return (Integer)pk;
		}

		if (pk instanceof Number)
		{
			return new Integer(((Number)pk).intValue());
		}

		return new Integer( pk.toString() );
	}
	
	//-----------------------------
	// Create methods.
	//-----------------------------

	/**
	* Creates an Attachment.
	*
	* @ejb.create-method view-type="local"
	*/
	public Integer ejbCreate(   Integer ownerId, 
								Integer ownerType, 
								int orderingIndex,
								String position, 
								byte[] content,
								String contentType ) throws CreateException
	{
		// Note : Unique ID is assigned by database auto-increment
		setOwnerId(ownerId);
		setOwnerType(ownerType);
		setOrderingIndex(orderingIndex);
		setPosition( position );	
		setContent(content);
		setContentType(contentType);
		setSize( content.length );     
		return null;
	}

	public void ejbPostCreate(  Integer ownerId, 
								Integer ownerType, 
								int orderingIndex,
								String position, 
								byte[] content,
								String contentType )
	{
        // Nothing here
	}


}