From the MediaTracker javadoc:The MediaTracker class is a utility class to track the status of a number of media objects. Media objects could include audio clips as well as images, though currently only images are supported
From the Tutorial, section "Loading Images":http://java.sun.com/docs/books/tutorial/uiswing/painting/usingImages.html
Basically, we use the mediatracker to be informed of when an image has been completely loaded. The resource you're pulling could be local, could be remote.. thusly, the complete data load time could vary. Since getImage() is non-blocking, this is how you know.
I suppose I could use those methods.. never really considered them. I'm pretty sure I've tried uploading non-image files, and I recall this catching them as not being images. but, it's been awhile, so ymmv.
cheers!
-- adam
I've never had any problems with this methodology.
From: "Brian McSweeney" <[EMAIL PROTECTED]> Reply-To: "Struts Users Mailing List" <[EMAIL PROTECTED]> To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]> Subject: RE: Validating uploaded file as an image only Date: Fri, 22 Aug 2003 13:38:11 -0000
Hi Adam, Cool! I had no clue that any of this was available. A few questions if you don't mind.
What is the purpose of using the MediaTracker?
I understand how using
Image makeimg = Toolkit.getDefaultToolkit().createImage( image.getFileData() );
will show you if it's a proper image, but I don't understand how the MediaTracker class helps? Does it just show if the image could be re-displayed or something?
If that assumption is correct, then the javadocs say that:
"If there is an error while loading or scaling an image, then that image is considered to have finished loading. Use the isErrorAny and isErrorID methods to check for errors. "
So should you perhaps use these "isErrorAny" or "isErrorID" methods too?
Any problems ever experienced?
Anyway, really appreciate this help, Brian
-----Original Message----- From: Adam L [mailto:[EMAIL PROTECTED] Sent: 22 August 2003 13:12 To: Struts Users Mailing List Subject: Re: Validating uploaded file as an image only
I do it the brute force way:
<---- snip ---------> FormFile image;
....
java.awt.Image makeimg = null;
try
{
makeimg = Toolkit.getDefaultToolkit().createImage(
image.getFileData() );// wait for the image to be loaded/created
Canvas cv = new Canvas();
MediaTracker media_tracker = new MediaTracker( cv ); // add image to the tracker
int id = 0;
media_tracker.addImage(makeimg,id); // try to wait for image to be loaded
// catch if loading was interrupted
media_tracker.waitForID(id);
// if we can't load it, it'll get tossed back from the
catch()// by now we should have a good image to deal with
// check on image dimensions
int imgw = makeimg.getWidth( cv );
int imgh = makeimg.getHeight( cv );} catch (......)
<----------------end snip---------->
I also check for file size (ie, dont' allow anything over 1M), and then image dimensions. The only thing I don't do is validate the mime-type. I haven't tried uploading images from a text browser (ie lynx or links), yet, to see what sort of mime-type it would attach.. but the ones from IE always seem to be fine.
cheers!
-- adam
----- Original Message ----- From: "Brian McSweeney" <[EMAIL PROTECTED]> To: "'Struts Users Mailing List'" <[EMAIL PROTECTED]> Sent: Friday, August 22, 2003 6:32 AM Subject: RE: Validating uploaded file as an image only
> PS - there was a discussion recently on how to improve the > Validator. > > > Validating an uploaded file based on mime type would be cool ! > > A quick search on the web led me to a company that does this > With a java api > > http://www.oop-reserch.com/mime_prop.html > > It seems in jdk1.4 you can actually validate based on the > binary pattern expected for a mime type. So if it is a gif, > you can check that the bit pattern of the uploaded file > matches that of a gif. > > This is apparently to avoid users uploading say a text file > named mytextfile.gif > > Now that would be nice :-) > Brian > > > -----Original Message----- > From: Brian McSweeney [mailto:[EMAIL PROTECTED] > Sent: 22 August 2003 11:13 > To: 'Struts Users Mailing List' > Subject: Validating uploaded file as an image only > > Hi everyone, > > I've managed to get the struts file upload working successfully, > using the struts FormFile class and the upload example. > > Cool :-) > > However, in my app, I only want images to be uploaded. > I'm going to store the images on disk and put the path of the > image file into the database. So I need to validate that only images > are getting uploaded, not other file-types. > > I know nothing really about how to do this. I could just check that > string returned by: > > FormFile.getContentType( ) > > is equal to image-gif, image-bnp, or image-jpeg. But is this enough? > > > Also, I have noticed that when I upload an image file and the little > Browser window pops up, if I select a gif image, but the file type > bar says "All files" then the file isn't recognized as an image. > It's recognized as an octet-stream. So does the browser window > specify the file type to the browser? > > Anyway, > > Hope someone can give me some advice, > As always, > Thanks very much, > Brian > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > >
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