CODEWITHSUNDEEP
javaurl
Azad
Azad

Reputation: 5055

Constructing a string from getResource("...") gives an output starts with "file:/"?

Lets consider image.png stored inside one of the project's package named icons, I usually get the icons via getResource() method :

String imgPath = getClass().getResource("/icons/image.png").toString();
//no problem with creating an ImageIcon with this path
Image img = new ImageIcon(imgPath).getImage();
//but the problem occures when trying to open this image through Desktop
//try-catch
Desktop.getDesktop().open(imagePath);
//or
File imgFile = new File(imgPath);
//error, this file does not exist!

I noticed that constructing a string from the URL gives the output that starts with file:/...., it makes no problem with loading the image, but opening the file not possible until removing file:/.

What's the benifit of file:/ that added to the string?
I thought that maybe the path is to a file, but I was wrong, even targeting to the folders gives this output.

Upvotes: 2

Views: 287

Answers (2)

Eric Jablow
Eric Jablow

Reputation: 7889

The method Class.getResources(String) returns a URL. This URL may be that of a local file, in which case it will begin with the file:/ protocol. However, your application or this class may run from a JAR file, and the resource may be contained in a JAR file. Sun created the jar:/ protocol for these cases. Then, the URL might be stringified as jar:file:/myapp.jar!/com/azad/images/image.png. So, instead of using file-based methods, use URL-based methods:

URL imgURL = getClass().getResource("/icons/image.png");
//no problem with creating an ImageIcon with this URL
Image img = new ImageIcon(imgURL).getImage();

ImageIcon has a constructor that takes a URL. Look at the JarURLConnection class too. You can't depend on Desktop to open your URL for you; that class only handles files. If your URL doesn't point at a plain file, you can't remove the file:/ from the string.

I did edit your post: you used img twice.

Upvotes: 1

David Kroukamp
David Kroukamp

Reputation: 36423

Its a URL path specific to files. Kinda how like web URLs have http://, https:// or ftp:// URL for file keeps that syntax thus file:/ was born .

For example copy an image like test.jpg to your C drive.

Than open your browser and type: file:/c:/test.jpg

hit ENTERand the image should be loaded.

What's the benefit of file:/ that added to the string?

No real benefits, besides the fact it becomes a valid URL, it can only be used as a URL and not as a valid path to a file, for that you would omit file:/ as you have seen

See file URI scheme for more

Upvotes: 1

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