and then I add a remote debug configuration to eclipse ide.
The remote debug config seems to work (in the debug windows appears the remote debug stack) but when I add a break point tand execute the web appl
it doesn't stop.
PS I tried also to configure the wls as a server with the eclipse plug in but I have the same problem.
Sounds like your source code in Eclipse and the class files on the remote application aren't in sync with each other. If the source code isn't the same code that produced the class you're debugging, a breakpoint may be set, but it might be set on a completely different statement within the class. And if you do hit the breakpoint, the Eclipse display won't match what the class is doing there.
An IDE is no substitute for an Intelligent Developer.