uk.co.weft.graphic
Class Graphic

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          uk.co.weft.maybeupload.MaybeUploadServlet
              uk.co.weft.htform.Servlet
                  uk.co.weft.graphic.Graphic

All Implemented Interfaces:

ResourceConsumer, java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

ExampleMappedImageServlet

public class Graphic

extends Servlet

A basic Servlet which outputs a GIF or JPEG, not an HTML page. Specialise.

Note: This class and its subclasses use image encoders by Jef Poskanzer (jef@acme.com), also avialable under BSD-style license. These encoders are not part of Jacquard, but can be downloaded from his site.

Configuration:

width ( integer)

the width of the image produced

height ( integer)

the height of the image produced

graphic_format (string)

one of 'gif', 'jpg, 'png'

Graphic Servlets under X11

Getting graphic servlets to work on UN*X style operating systems is tricky. The following conditions all have to be met:

• The machine must be running an X Server (may be Xvfb)
• The user the servlet engine runs as must be able to communicate with the X Server
• The DISPLAY environment variable must be passed to the servlet engine process. If using Apache JServ, see 'wrapper.env' in jserv.properties

Version:

$Revision: 1.2.4.1 $ This revision: $Author: simon $

Author:

Simon Brooke

See Also:

Serialized Form

Field Summary

protected java.lang.String	contentType my content type
protected java.lang.String	format my graphics format
protected int	height The height of my canvas
protected int	width The width of my canvas

Fields inherited from class uk.co.weft.htform.Servlet

calendar, conf, CONTENTTYPECONFIGTOKEN, cookieDomain, cookiePath, COOKIESCONFIGTOKEN, cookieTTL, dbPassword, dbUrl, dbUsername, debug, DEBUGCONFIGTOKEN, driverName, embedded, here, identity, localeMagicToken, LOCALEMAGICTOKEN, outputStreamMagicToken, OUTPUTSTREAMMAGICTOKEN, parsePathInfo, PATHINFOMAGICTOKEN, ready, redirectMagicToken, REDIRECTMAGICTOKEN, requestMagicToken, REQUESTMAGICTOKEN, resourceBundleName, responseMagicToken, RESPONSEMAGICTOKEN, servletMagicToken, SERVLETMAGICTOKEN, sessionMagicToken, SESSIONMAGICTOKEN, USEHTTPSCONFIGTOKEN, zone

Fields inherited from class uk.co.weft.maybeupload.MaybeUploadServlet

allowOverwrite, maxUpload, saveUploadedFilesToDisk, silentlyRename, uploadDir, uploadDirPath, uploadDirURL

Fields inherited from interface uk.co.weft.htform.ResourceConsumer

RESOURCEBUNDLEMAGICTOKEN

Constructor Summary

Graphic()

Method Summary

protected void	generateContent(Context context) Really perform service of an HTTP GET request, by printing myself on the response stream
void	init(Context config) Initialisation: set up my variables from configuration
protected void	paintImage(java.awt.Graphics g) Paint the desired image onto this graphics context.

Methods inherited from class uk.co.weft.htform.Servlet

addCookie, addCookie, coerceCookiesToContext, coerceToContext, coerceToContext, coerceToContext, coerceToContext, coerceToUrl, createContext, doGet, doPost, fixupMagicValues, getCalendar, getContentType, getDebug, getLocale, getOutputStream, getResource, getResourceString, getServletInfo, grs, grs, handleAction, handleCookies, handleRedirect, init, makeReady, outputRedirectBlock, setCookieValues, storeOnSession, whinge, whinge

Methods inherited from class uk.co.weft.maybeupload.MaybeUploadServlet

doDelete, doHead, doOptions, doPut, doTrace, getUploadDir, getUploadURL, service

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Field Detail

width

protected int width

The width of my canvas

height

protected int height

The height of my canvas

contentType

protected java.lang.String contentType

my content type

format

protected java.lang.String format

my graphics format

Constructor Detail

Graphic

public Graphic()

Method Detail

init

public void init(Context config)
          throws InitialisationException

Initialisation: set up my variables from configuration

Overrides:

init in class Servlet

Throws:

InitialisationException

paintImage

protected void paintImage(java.awt.Graphics g)

Paint the desired image onto this graphics context. This is the one method that subclasses should need to specialise

generateContent

protected void generateContent(Context context)
                        throws java.lang.Exception

Really perform service of an HTTP GET request, by printing myself on the response stream

Specified by:

generateContent in class Servlet

Parameters:

context - the context in which to generate this content.

Throws:

java.lang.Exception