CODEWITHSUNDEEP
javaresourcesappletclasspath
WarrenB
WarrenB

Reputation: 2185

Loading all files in a directory in a Java applet

How would one go about programatically loading all the resource files in a given directory in a JAR file for an applet? The resources will probably change several times over the lifetime of the program so I don't want to hardcode names in.

Normally I would just traverse the directory structure using File.list(), but I get permission issues when trying to do that within an applet. I also looked at using an enumeration with something line ClassLoader.getResources() but it only finds files of the same name within the JAR file.

Essentially what I want to do is (something like) this:

ClassLoader imagesURL = this.getClass().getClassLoader();
MediaTracker tracker = new MediaTracker(this);
Enumeration<URL> images = imagesURL.getResources("resources/images/image*.gif");
while (images.hasMoreElements()){
    tracker.add(getImage(images.nextElement(), i);
    i++;
}

I know I'm probably missing some obvious function, but I've spent hours searching through tutorials and documentation for a simple way to do this within an unsigned applet.

Upvotes: 1

Views: 1065

Answers (1)

dma_k
dma_k

Reputation: 10639

You can do it in two ways:

  1. Rename your images, so you can enumerate them via some algorithm (e.g. image_1, image_2, image_3), then you can collect all resources you need in one go.

  2. Otherwise you need to code a lot. The idea is that you have to:

    • determine the path to your JAR file:

      private static final String ANCHOR_NAME = "some resource you know";

URL location = getClass().getClassLoader().getResource(ANCHOR_NAME);
URL jarLocation;
String protocol = location.getProtocol();
if (protocol.equalsIgnoreCase("jar"))
{
    String path = location.getPath();
    int index = path.lastIndexOf("!/" + ANCHOR_NAME);
    if(index != -1)
       jarLocation = new URL(path.substring(0, index));
}
if (protocol.equalsIgnoreCase("file"))
{
    String string = location.toString();
    int index = string.lastIndexOf(ANCHOR_NAME);
    if(index != -1)
        jarLocation = new URL(string.substring(0, index));
}

    • open it as java.util.jar.JarFile

      JarFile jarFile = new JarFile(jarLocation);

    • iterate through all entries and match their name with a given mask

      for (Enumeration entries = jarFile.entries(); entries.hasMoreElements();)
{
     JarEntry entry = (JarEntry) entries.nextElement();
     String entryPath = entry.getName();
     if (entryPath.endsWith(".jpg"))
     {
        // do something with it
     }
}

For additional code support, I will refer you to Spring PathMatchingResourcePatternResolver#doFindPathMatchingJarResources().

Upvotes: 1

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