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From Christopher Schultz <>
Subject Re: [OT] storing images
Date Fri, 13 May 2011 14:47:55 GMT
Hash: SHA1


Marking off-topic because this has nothing whatsoever to do with Tomcat.

On 5/11/2011 5:06 PM, alexis wrote:
> For real time purposes, im building images

I get it.

> We'll going to images, what i store in servletcontext is NOT
> practically the image, as those images are being constructed using
> jfreechart, what i store in memory is the JFreeChart object  (and
> inside the JFreeChart object i store some other objects like the
> dataseries, Custom Labels, etc)

Ouch. You may be storing much more in memory than necessary. When you
get new data, do you update the existing JFreeChart object, or do you
create one from scratch (new series, etc.) each time the image is
requested /and/ needs to be re-generated?

> after i store this object inside
> servletcontext, my servet returns out.println("<img
> src=\"getImage?img=skill1_239423948.png\">"); so the ajax script sets
> this as innerhtml for a div in the jsp, and the jsp calls getimage
> servlet requesting the image.


> What happens here is
> 1. _239423948 is a random value that i add to avoid browser caching
> of the image, so as i receive it, it's discarded

You could also use a random request parameter value, but there's little
practical difference.

> 2. i read the JFreeChart object from the servletcontext regarding skill1
> 3. i call a method from the object that is called writeChartAsJPEG
> (self explaining) , set the response type to image/jpeg and then i do
> out.println(JFreeChart); which renders the image that is finally shown
> by the browser.

Hopefully not "println" as that may corrupt your image and will
definitely add an unnecessary trailing newline.

So, you re-encode the image every time it's served to a client. I'm
suggesting that when you render the JFreeChart, you go all the way to a
JPEG (or image format of your choice) and store /that/ in the

> It's working without any problem, im constantly profiling the webapp
> to see how it behaves and before/after the image implementation i
> have noticed no change at all on the memory and cpu usage.

I think you'll notice that CPU usage is reduced dramatically if you
aren't re-encoding the image upon every request. Inverse cosine
transforms aren't free ;)

> What i dont know exactly is how much memory uses a JFreeChart object
> stored in the servletcontext, if there's a way to know it please let me
> know so i can check it and let you know.

What profiler are you using? I use YourKit and it tells me the sizes of
object trees fairly easily.

If you store the raw bytes of the JPEG image in memory, they will take
up exactly the same size as the file does on disk. So if you look at the
image information from your web browser and it says, say, 180k for the
image, then that's how much memory it will take when it's sitting in
your ServletContext.

- -chris
Version: GnuPG v1.4.10 (MingW32)
Comment: Using GnuPG with Mozilla -


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