dekoh.portal.image
Class AbstractResizeImageServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          dekoh.portal.util.FileServer
              dekoh.portal.image.AbstractResizeImageServlet

All Implemented Interfaces:

Serializable, Servlet, ServletConfig

public abstract class AbstractResizeImageServlet
extends FileServer

Many DigitalObjects may have a photo file to identify them. A Music Album has Covert Art image, A Book has a cover page image etc. Applications dealing with digital objects whose preview may include a resized image can extends this servlet.

This Servlet works off a directory where images once resized are cached. Subsequent HTTP requests to get the resized images are served from this cache unless the SourceFile is modified.

This servlet also overrides FileServer.getLastModified(javax.servlet.http.HttpServletRequest) to optimize network badwidth when the cached image file is not updated since previous get request from the same User-Agent.

Note : It is advisable that the servlets extending this class be loadeded on startup.

Since:

Jun 22, 2007

See Also:

ResizeImageCache, ImageResizer.DEFAULT_COMPRESSION_QUALITY, Serialized Form

Field Summary

protected static PLogger

logger

Fields inherited from class dekoh.portal.util.FileServer

FILE_EXT_HEADER, FILE_TO_SERVE, UNKNOWN

Constructor Summary

AbstractResizeImageServlet()

Method Summary

protected abstract DigitalObject	getAccessingDigitalObject(HttpServletRequest request, int id)
protected File	getCacheDir(ServletContext servletContext) Will point to public_html/${applicationContextRoot}/WEB-INF/cache.
protected EXIFOrientation	getEXIFOrientation(DigitalObject digitalObject) Some photos may be better viewed when oriented in a perticulat direction, for such pictures resized image should also be oriented in same direction as the original image.
protected File	getRequestedFile(HttpServletRequest request) Serves the resource requested in FileServer.doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) or FileServer.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method of this servlet.
protected ResizeImageCache	getResizeImageCache(HttpServletRequest request)
protected abstract File	getSourceImageFile(DigitalObject digitalObject)
protected File	resize(HttpServletRequest request)
protected ImageSize	resizeToWhat(HttpServletRequest request)
protected int	resizeWhat(HttpServletRequest request)

Methods inherited from class dekoh.portal.util.FileServer

authorizedToAccessCachedCopy, copyStream, doGet, doPost, getLastModified, handleExceptionInLastModified, serveRequestedFile

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

protected static final PLogger logger

Constructor Detail

AbstractResizeImageServlet

public AbstractResizeImageServlet()

Method Detail

getCacheDir

protected File getCacheDir(ServletContext servletContext)

Will point to public_html/${applicationContextRoot}/WEB-INF/cache. Once initialized this variable never changes.

getAccessingDigitalObject

protected abstract DigitalObject getAccessingDigitalObject(HttpServletRequest request,
                                                           int id)

getSourceImageFile

protected abstract File getSourceImageFile(DigitalObject digitalObject)
                                    throws IOException

Throws:

IOException

getRequestedFile

protected final File getRequestedFile(HttpServletRequest request)
                               throws IOException

Description copied from class: FileServer

Serves the resource requested in FileServer.doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) or FileServer.doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) method of this servlet. Bytes of this file will be written to output stream of the HttpServletResponse.

Specified by:

getRequestedFile in class FileServer

Parameters:

request - - HttpServletRequest

Returns:

File if the return value is null or a File that does not exist on disc, a 404/Page not found response will be sent.

Throws:

IOException - throws when could not create the requried file

resize

protected File resize(HttpServletRequest request)
               throws IOException

Throws:

IOException

getResizeImageCache

protected ResizeImageCache getResizeImageCache(HttpServletRequest request)

getEXIFOrientation

protected EXIFOrientation getEXIFOrientation(DigitalObject digitalObject)

Some photos may be better viewed when oriented in a perticulat direction, for such pictures resized image should also be oriented in same direction as the original image.

Override this method if this information can be learnt from the digitalObject.

Parameters:

digitalObject -

Returns:

default value, indicating Top left

resizeWhat

protected int resizeWhat(HttpServletRequest request)

resizeToWhat

protected ImageSize resizeToWhat(HttpServletRequest request)