/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.markup.html.image.resource;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Blob;
import java.sql.SQLException;

import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.request.resource.DynamicImageResource;
import org.apache.wicket.util.io.Streams;


/**
 * An ImageResource subclass for dynamic images that come from database BLOB fields. Subclasses
 * override getBlob() to provide the image data to send back to the user. A given subclass may
 * decide how to produce this data and whether/how to buffer it.
 * 
 * @author Eelco Hillenius
 */
public abstract class BlobImageResource extends DynamicImageResource
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * Construct.
	 * 
	 * @param format
	 */
	public BlobImageResource(String format)
	{
		super(format);
	}

	/**
	 * Construct.
	 */
	public BlobImageResource()
	{
	}

	@Override
	protected byte[] getImageData(Attributes attributes)
	{
		try
		{
			Blob blob = getBlob(attributes);
			if (blob != null)
			{
				InputStream in = blob.getBinaryStream();
				ByteArrayOutputStream out = new ByteArrayOutputStream();
				Streams.copy(in, out);
				return out.toByteArray();
			}
			return new byte[0];
		}
		catch (SQLException e)
		{
			throw new WicketRuntimeException("Error while reading image data", e);
		}
		catch (IOException e)
		{
			throw new WicketRuntimeException("Error while reading image data", e);
		}
	}

	/**
	 * Gets the BLOB (Binary Large OBject) that holds the raw image data.
	 *
	 * @param attributes
	 *      the current web attributes (request, response, parameters)
	 * @return the BLOB
	 */
	protected abstract Blob getBlob(Attributes attributes);
}