Own URLClassloader...

[Christian Neudorfer]

Hi, I want to hot-swap the implementation of a class which is packed in a jar-file.
for example:

URL url = ...
String compName = ...
URLClassLoader loader = new URLClassLoader(new URL[] {url});
Component c = (Component)loader.loadClass(compName).newInstance();

Later I want to swap the implementation by providing a new jar-file.

URL newUrl = ...
URLClassLoader newLoader = new URLClassLoader(new URL[] {newUrl});
Component c = (Component)loader.loadClass(compName).newInstance();

This doesn't work. The new class gets never loaded.
I thought, that I have to write my own classloader to change the order of searching for classes in the method

 loadClass(...) 

.
Everytime I try to call

 findClass(...) 

, I get the following exception:
java.lang.ClassNotFoundException: com.test.compA.ServiceAImpl
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at com.test.OwnClassLoader.loadClass(OwnClassLoader.java:43)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.test.ComponentManager.loadComponent(ComponentManager.java:176)
at myTest.MyTest.main(MyTest.java:12)
Caused by: java.util.zip.ZipException: invalid block type
at java.util.zip.InflaterInputStream.read(Unknown Source)
at sun.misc.Resource.getBytes(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
The ZipException does occur, when i call the method

 findClass  

.
Any ideas? Thx in advance...
Chris

[Jean-Francois Briere]

This doesn't work. The new class gets never loaded.

It should work with URLClassLoader.
You must be sure that your jar files are NOT in the class path, so that the bootstrap class loader does not see them.