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/*
* This file is part of the Echo Web Application Framework (hereinafter "Echo").
* Copyright (C) 2002-2009 NextApp, Inc.
*
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (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.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*/
package nextapp.echo.webcontainer.service;
import java.io.IOException;
import javax.servlet.http.HttpServletResponse;
import nextapp.echo.app.AwtImageReference;
import nextapp.echo.app.ImageReference;
import nextapp.echo.app.StreamImageReference;
import nextapp.echo.webcontainer.Connection;
import nextapp.echo.webcontainer.ContentType;
import nextapp.echo.webcontainer.Service;
import nextapp.echo.webcontainer.SynchronizationException;
import nextapp.echo.webcontainer.UserInstance;
import nextapp.echo.webcontainer.util.PngEncoder;
/**
* A Service which renders stream image references (including ResourceImageReferences and
* AwtImageReferences.
*/
public class ImageService
implements Service {
/** Service identifier. */
private static final String SERVICE_ID = "Echo.Image";
/** Singleton instance of this Service. */
public static final ImageService INSTANCE = new ImageService();
/** Image identifier URL parameter. */
private static final String PARAMETER_IMAGE_UID = "iid";
/** URL parameters (used for creating URIs). */
private static final String[] URL_PARAMETERS = new String[]{PARAMETER_IMAGE_UID};
/**
* @see nextapp.echo.webcontainer.Service#getId()
*/
public String getId() {
return SERVICE_ID;
}
/**
* @see nextapp.echo.webcontainer.Service#getVersion()
*/
public int getVersion() {
return 0; // Enable caching.
}
/**
* Creates a URI to retrieve a specific image for a specific component
* from the server.
*
* @param userInstance the relevant application user instance
* @param imageId the unique id to retrieve the image from the
* ContainerInstance
*/
public String createUri(UserInstance userInstance, String imageId) {
return userInstance.getServiceUri(this, URL_PARAMETERS, new String[]{imageId});
}
/**
* Renders the specified image to the given connection.
* Implementations should set the response content type, and write image
* data to the response OutputStream.
*
* @param conn the Connection on which to render the image
* @param imageReference the image to be rendered
* @throws IOException if the image cannot be rendered
*/
public void renderImage(Connection conn, ImageReference imageReference)
throws IOException {
if (imageReference instanceof StreamImageReference) {
renderStreamImage(conn, imageReference);
} else if (imageReference instanceof AwtImageReference) {
renderAwtImage(conn, imageReference);
} else {
throw new SynchronizationException("Unsupported image type: " + imageReference.getClass().getName(), null);
}
}
/**
* Renders an AwtImageReference.
*
* @param conn the Connection to which the image should be rendered
* @param imageReference the image to render
* @throws IOException
*/
private void renderAwtImage(Connection conn, ImageReference imageReference)
throws IOException {
try {
PngEncoder encoder = new PngEncoder(((AwtImageReference) imageReference).getImage(), true, null, 3);
conn.setContentType(ContentType.IMAGE_PNG);
encoder.encode(conn.getOutputStream());
} catch (IOException ex) {
// Internet Explorer appears to enjoy making half-hearted requests for images, wherein it resets the connection
// leaving us with an IOException. This exception is silently eaten.
// It would preferable to only ignore SocketExceptions, however the API documentation does not provide
// enough information to suggest that such a strategy would be adequate.
}
}
/**
* Renders a StreamImageReference.
*
* @param conn the Connection to which the image should be rendered
* @param imageReference the image to render
* @throws IOException
*/
private void renderStreamImage(Connection conn, ImageReference imageReference)
throws IOException {
try {
StreamImageReference streamImageReference = (StreamImageReference) imageReference;
conn.setContentType(new ContentType(streamImageReference.getContentType(), true));
streamImageReference.render(conn.getOutputStream());
} catch (IOException ex) {
// Internet Explorer appears to enjoy making half-hearted requests for images, wherein it resets the connection
// leaving us with an IOException. This exception is silently eaten.
// It would preferable to only ignore SocketExceptions, however the API documentation does not provide
// enough information to suggest that such a strategy would be adequate.
}
}
/**
* Gets the image with the specified id.
*
* @param userInstance the UserInstance from which the image was requested
* @param imageId the id of the image
* @return the image if found, null otherwise.
*/
public ImageReference getImage(UserInstance userInstance, String imageId) {
return (ImageReference) userInstance.getIdTable().getObject(imageId);
}
/**
* @see nextapp.echo.webcontainer.Service#service(nextapp.echo.webcontainer.Connection)
*/
public void service(Connection conn)
throws IOException {
UserInstance userInstance = (UserInstance) conn.getUserInstance();
if (userInstance == null) {
serviceBadRequest(conn, "No container available.");
return;
}
String imageId = conn.getRequest().getParameter(PARAMETER_IMAGE_UID);
if (imageId == null) {
serviceBadRequest(conn, "Image UID not specified.");
return;
}
ImageReference imageReference = getImage(userInstance, imageId);
if (imageReference == null) {
serviceBadRequest(conn, "Image UID is not valid.");
return;
}
renderImage(conn, imageReference);
}
/**
* Services a bad request.
*
* @param conn the Connection
* @param message the error message
*/
private void serviceBadRequest(Connection conn, String message) {
conn.getResponse().setStatus(HttpServletResponse.SC_BAD_REQUEST);
conn.setContentType(ContentType.TEXT_PLAIN);
conn.getWriter().write(message);
}
}
