org.apache.wicket.request.resource.DynamicImageResource.java Source code

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Here is the source code for org.apache.wicket.request.resource.DynamicImageResource.java

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/*
 * 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.request.resource;

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;

import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.time.Time;

/**
 * Base class for dynamically generated ImageResources.
 */
public abstract class DynamicImageResource extends AbstractResource {
    private static final long serialVersionUID = 1L;

    /** The image type */
    private String format = "png";

    /** The last modified time of this resource */
    private Time lastModifiedTime;

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

    /**
     * Creates a dynamic resource from for the given locale
     * 
     * @param format
     *            The image format ("png", "jpeg", etc)
     */
    public DynamicImageResource(String format) {
        setFormat(format);
    }

    /**
     * @return Returns the image format.
     */
    public synchronized final String getFormat() {
        return format;
    }

    /**
     * Sets the format of this resource
     * 
     * @param format
     *            The format (jpg, png or gif..)
     */
    public synchronized final void setFormat(String format) {
        Args.notNull(format, "format");
        this.format = format;
    }

    /**
     * set the last modified time for this resource.
     * 
     * @param time
     */
    protected synchronized void setLastModifiedTime(Time time) {
        lastModifiedTime = time;
    }

    /**
     * @param image
     *            The image to turn into data
     * @return The image data for this dynamic image
     */
    protected byte[] toImageData(final BufferedImage image) {
        try {
            // Create output stream
            final ByteArrayOutputStream out = new ByteArrayOutputStream();

            // Write image using any matching ImageWriter
            ImageIO.write(image, format, out);

            // Return the image data
            return out.toByteArray();
        } catch (IOException e) {
            throw new WicketRuntimeException("Unable to convert dynamic image to stream", e);
        }
    }

    /**
     * Get image data for our dynamic image resource. If the subclass regenerates the data, it
     * should set the {@link DynamicImageResource#setLastModifiedTime(Time)} when it does so. This
     * ensures that image caching works correctly.
     * 
     * @param attributes
     *            the context bringing the request, response and the parameters
     * 
     * @return The image data for this dynamic image. {@code null} means there is no image and 404
     *         (Not found) response will be return.
     */
    protected abstract byte[] getImageData(Attributes attributes);

    protected void configureResponse(final ResourceResponse response, final Attributes attributes) {

    }

    @Override
    protected ResourceResponse newResourceResponse(final Attributes attributes) {
        final ResourceResponse response = new ResourceResponse();

        if (lastModifiedTime != null) {
            response.setLastModified(lastModifiedTime);
        } else {
            response.setLastModified(Time.now());
        }

        if (response.dataNeedsToBeWritten(attributes)) {
            response.setContentDisposition(ContentDisposition.INLINE);

            final byte[] imageData = getImageData(attributes);
            if (imageData == null) {
                response.setError(HttpServletResponse.SC_NOT_FOUND);
            } else {
                response.setContentType("image/" + getFormat());
                response.setWriteCallback(new WriteCallback() {
                    @Override
                    public void writeData(final Attributes attributes) {
                        attributes.getResponse().write(imageData);
                    }
                });

                configureResponse(response, attributes);
            }
        }

        return response;
    }
}