Question

I have a memory class loader (here) that I am using in a custom Minecraft launcher.

Memory Class Loader

Whenever I load up Minecraft (a Java LWJGL game), I am getting the following error:

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LWJGL Version: 2.4.2
java.lang.IllegalArgumentException: input == null!
at javax.imageio.ImageIO.read(Unknown Source)
at lc.<init>(SourceFile:21)
at gi.<init>(SourceFile:10)
at net.minecraft.client.Minecraft.a(SourceFile:254)
at net.minecraft.client.Minecraft.run(SourceFile:657)
at java.lang.Thread.run(Unknown Source)

I am creating the class loader like this:

Base.cLoader = new CLoader(
    GameUpdater.classLoader,
    new JarInputStream(new ByteArrayInputStream(jarFileBytes)));

As you can see, it manages to load up the first part then suddenly after LWJGL Version it crashes with “input == null”.

Edit – Here is the new getResource method.

The error is on “URL()”, as shown.

Code:

public URL getResource(final String name) {
    URL url = new URL() { public InputStream openStream() {
        return new ByteArrayInputStream((byte[])others.get(name));
    }};

    return url;
}

Answer 1

A wild guess… it could be this: Warning: URLs for this are not yet implemented! You cannot call getResource() or getResources()!

So your code expects to retrieve an image from the JAR using the unimplemented method. An equivalent of this is probably being executed:

ImageIO.read(memClassLoader.getResource(someString));

Except that, as we have seen, the Error thrown from getResource is getting ignored and null being used as the value. ImageIO.read goes like this:

public static BufferedImage read(URL input) throws IOException {
    if (input == null) {
        throw new IllegalArgumentException("input == null!");
    }

    InputStream istream = null;
    try {
        istream = input.openStream();
    } catch (IOException e) {
        throw new IIOException("Can't get input stream from URL!", e);
    }
}

Sounds familiar? So, this is roughly what you need to implement:

public URL getResource(final String name) {
  try {
    return new URL("", "", 0, "",
        new URLStreamHandler() { public URLConnection openConnection(URL url) {
          return new URLConnection(url) {
            public void connect() {}
            public InputStream getInputStream() {
              // return the appropriate InputStream, based on the name arg
            }
          };
        }});
  } catch (MalformedURLException e) { throw new RuntimeException(e); }
}