lt.monarch.chart.servlet
Class ImageServlet

java.lang.Object
  HttpServlet
      lt.monarch.chart.servlet.ImageServlet

Direct Known Subclasses:

ChartServlet

public abstract class ImageServlet
extends HttpServlet

Image encoding servlet. Every HTTP request triggers the createImage method. The returned image is then encoded and returned to the browser.

Field Summary

Modifier and Type	Field and Description
protected AbstractEncoder	encoder encoder used for image encoding

Constructor and Description

ImageServlet()

Method Summary

Modifier and Type	Method and Description
protected abstract java.awt.Image	createImage(HttpServletRequest req) Requests an image to be created for the HTTP request.
void	doGet(HttpServletRequest req, HttpServletResponse res) Called by the server to allow a servlet to handle a GET request.
protected AbstractEncoder	getEncoder() Returns an encoder used to encode image.

Methods inherited from class java.lang.Object

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

Field Detail

encoder

protected AbstractEncoder encoder

encoder used for image encoding

Constructor Detail

ImageServlet

public ImageServlet()

Method Detail

createImage

protected abstract java.awt.Image createImage(HttpServletRequest req)
                                       throws ServletException

Requests an image to be created for the HTTP request.

Parameters:

req - servlet request

Returns:

image to be returned to the browser

Throws:

ServletException - if the request for the GET could not be handled

getEncoder

protected AbstractEncoder getEncoder()

Returns an encoder used to encode image. The default implementation returns an instance of lt.monarch.image.png.PNGEncoder. To use other encoder you should override this method so that it would return instance of required encoder.

Returns:

encoder used to encode image

doGet

public final void doGet(HttpServletRequest req,
                        HttpServletResponse res)
                 throws ServletException,
                        java.io.IOException

Called by the server to allow a servlet to handle a GET request. Triggers the createImage method. The returned image is then encoded and returned to the browser.

Parameters:

req - an HttpServletRequest object that contains the request the client has made of the servlet

res - an HttpServletResponse object that contains the response the servlet sends to the client

Throws:

ServletException - if the request for the GET could not be handled

java.io.IOException - if an input or output error is detected when the servlet handles the GET request