Accessing ressources in jar file

Question

Hi,
I need some help with jar files, please.
The concept of jar files is quite new to me and I din't fully unterstand it yet I guess...
I'm loading an image by
ImageIcon image = new ImageIcon("image.gif");
now I'd like to pack that image into a jar file, for simplifying reasons when using more files, which is not the problem, so far.
But how can I access that file then in my java programm?
Do I have to use the JarFile.getInputStream() method or what?
Is there no 'easier' way, avoiding Streams and Readers?
Can I hand over the JarEntry of my gif file to the ImageIcon constructor
somehow instead of the file?
Thanks for help..

Answer 1

I guess you've set me on the right course, but I am
afraid I don't really understand the concept of those
class loaders, either.
I read the part on jar files and extensions in the
java tutorial(and therefore on class loaders, too),
but I still don' get it.JAR Files and classloaders are two different concepts. The JAR file is merely a packaging method for Java code. Classloaders on the other hand, are the way the JVM finds the code classes. All a classloader does is load binary data from somewhere and pass it to the JVM for execution. See http://java.sun.com/j2se/1.4/docs/api/java/lang/ClassLoader.html for more info.
The relevant code part we're talking about here is
used in a class extending JPanel , so thats what you
get by performing getClass(), the running instance of
a JPanel subclass.
but obviousely there is no getResource() method in
that type of class.Really? http://java.sun.com/j2se/1.4/docs/api/java/lang/Class.html#getResource(java.lang.String)
Of course, Object.getClass().getResource() is just a convienence method for Object.getClass().getClassLoader().getResource(). Just as the ClassLoader can load the binary data that creates a Class object that lends itself to the execution of the Object you're loading, it can load other forms of binary data from the same location.
what I don't understand is: where does this method
come frome? do I have to add somehow a classlistener
instance to my class? or add an implementation in the
code of my class, providing a getResource method? A Class object (See http://java.sun.com/j2se/1.4/docs/api/java/lang/Class.html) is merely a "wrapper" object that represents the running code. It exposes the methods and fields for access. Normally Class is used behind the scenes, but it can be used to execute dynamically loaded code.
You don't need to "add" a classloader. A classloader loaded the code that you are running. When it loads the class, it stamps it with its signature so that you know who loaded it.
I guess you see now I really have no idea how the
classloader system works ;)
(and believe me I'm not asking dumb questions berfore
trying to solve the prob by myself....)
Thanks for any additional helpNo prob. :-)