Re: Loading a class using the applet class loader
Andr? Wagner wrote:
Hello,
I'm loading classes during the execution of a applet, like this:
ClassLoader cl = getClass().getClassLoader();
Class c = cl.loadClass(className);
MyObject o = (MyObject)c.newInstance();
It works fine, but if the class is big, the applet execution hangs
until the whole class is downloaded from the server and loaded. Is
there any way I can download the class (showing the user a progressbar
for that) and load the bytecode? I tried using the defineClass method,
but I can't overwrite in the applet class loader it because of the
applet security restrictions.
I don't see why not, but I'm not an expert, so take this with a grain of
salt.
Subclass an appropriate classloader so you have your own classloader to
play with. Probably, you will need to subclass URLClassLoader.
Override the findClass() method to check the size of any class it finds,
and throw up a progress bar if the size is over X, where X is some
number of bytes that you think will take "too long" to download. Then
use your new classloader to load the rest of the app (you'll need a
small stub at the beginning of the app to start things off).
Alternate, make your own classloader and override it's findClass()
method. Make a second class that just does a regular old HTTP or FTP
download of a lot of different stuff: several classes and resources. In
other words, this second class downloads everything in one go. Your own
classloader in this case will know about this second class and look
there for any files first, before handing them off to the default
classloader. This way, you can download everything in one shot, and
have it available so the user doesn't have to wait.
Just a couple of ideas. I've never tried this, so good luck.