Re: Determining if an image exists
Re: Determining if an image exists
- Subject: Re: Determining if an image exists
- From: Colin Clark <email@hidden>
- Date: Thu, 17 Feb 2005 12:15:46 -0500
Hi David,
I'm not sure if this is what you're looking for, but off the top of my head, here's a suggestion.
If already have a URL to your resource, you can always instantiate a URL object for it, open a connection, and then check the status code that is returned from the Web server. Assuming the images are served up by the Web server, I assume you'll get a 404 (file not found) if the image doesn't actually exist, and you should get a 200 if everything was OK. The downside to this approach--as far as I know--is that you have to actually connect to the server and pull the image down just to check if it's there. Here's some sample code:
String imageURL; // Assume this exists and always begins with http://
URL urlForImage = new URL(imageURL);
HttpURLConnection connection = (HttpURLConnection) urlForImage.openConnection();
if (connection.getResponseCode() == 200)
// The image exists on the Web server.
else
// Do something else.
Alternatively, if your app is guaranteed to live on the same box as the Web server, you could simply open a File object to the location of your URL relative to the document root, and use the exists() method to see if it's actually there. This approach is more brittle because it assumes that your application and Web server are closely coupled.
I hope that helps,
Colin
On Thursday, February 17, 2005, at 10:02 AM, David Griffith wrote:
Hi all,
Just wondered if anyone has a simple approach to use Java in WebObjects to determine if an image (or file) exists at a URL.
What I’m doing is fairly simple, I want to display up to 4 images which have dynamic URL’s. I want to check first if the image (URL) actually exists on the web server. If not, I don’t want to display it.
Any suggestions?
Kind regards,
David. _______________________________________________
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---
Colin Clark
Dynamic Web and Database Development Lead,
Resource Centre for Academic Technology,
University of Toronto
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