Hello Vladimir,
Thursday, March 15, 2001, 12:25:24 PM, you wrote:
VG> What you describe should work... Unless Tomcat web-app CL doesn't
VG> adhere to standard CL delegation rules. Where did you put your classes?
VG> I think $TOMCAT_HOME/classes is automatically appended to system classpath
VG> by startup script.
VG> I don't think _bootstrap_ CL is the one
VG> that's loading classes if you put them on system classpath.
VG> Probably it's SystemClassLoader. You can test
VG> it like this from your servlet to find out what's going on:
VG> _statesBean=
VG> getServletContext().getAttribute(StatesBean.STATES_BEAN_NAME);
VG> ClassLoader cl = _statesBean.getClass().getClassLoader();
VG> if (cl.getParent() == null)
VG> System.out.println("Bootstrap Class Loader");
VG> if (cl == ClassLoader.getSystemClassLoader())
VG> System.out.println("System Class Loader")
VG> if (cl == this.getClass().getClassLoader())
VG> System.out.println("Current WebApps Class Loader");
In case StatesBean in web-inf/classes - "Current WebApps Class Loader"
In case StatesBean in %CLASSPATH% - "System Class Loader"
VG> BTW, did you try to use reflection like I suggested before
VG> (scroll down...)?
Not yet. :)
<from previous post>
> >> Now, when your servlet class is loaded, Tomcat asks the webapp class
> >> loader to load it. Following the standard Java delegation model, the web
> >> app class loader first asks it's parent class loader to try to find the
> >> class -- and so on up the hierarchy. If your servlet class is actually in
> >> WEB-INF/classes or WEB-INF/lib, all of these attempts to delegate upwards
> >> will fail. Therefore, the web app class loader will load the class
> >> itself.
> >>
> >> The same thing happens for every other class that your servlet references
> >> -- it gets loaded by whichever class loader finds that class. If the load
> >> happens from a class loader *above* the calling class's class loader, that
> >> is fine. However, trouble occurs if you try the opposite direction,
> >> because there are no links *downward* in the class loader hierarchy.
</from previous post>
I have my StatesBean loaded by SystemClassLoader. OK.
MyServlet by WebAppLoader. Good.
So when WebAppLoader reloads my servlet it should ask its parents
about loaded class. Ang guess what? StatesBean loaded already with
SystemClassLoader. What's wrong with it?
Why do I get java.lang.NullPointerException in
_statesBean=
getServletContext().getAttribute(StatesBean.STATES_BEAN_NAME);
after reloading servlets?
--
Best regards,
Andrey mailto:[EMAIL PROTECTED]
