Hi Charlie,
> did you restart tomcat since your class is in common/classes? Yes, I did. > you may want to wrap the loadlibrary() in a singleton. I'm not sure that you > can use Class.forName on a class with no methods or fields. You may also > want to see if the native functions are available even if the Class.forName > is throwing an error. The static block should be run automatically by the > classloader, but I'm not sure if it does this when the class is loaded, or > when it is first called. > > you do want your class in /common/classes so that it can only be loaded > once. This is very important because I would like to access the library from several different applications. > I have my library on the system path(win2k) and it works fine. If you had it > working before(if only the first time), then the library was in the right > place. This is the part that's giving me a headache. I don't know why it makes a difference if initialise it in static block in a servlet or my InitMapserver class. Andreas > > -----Original Message----- > > From: Andreas Hirner [mailto:[EMAIL PROTECTED]] > > Sent: Tuesday, June 25, 2002 7:41 AM > > To: Tomcat Users List > > Cc: [EMAIL PROTECTED] > > Subject: Re: Native library cannot be loaded twice > > > > > > Hi, > > > > > A bit off-topic (this goes into native programming), but there is > > something > > > whirling through my head: > > > > > > Static classes/members are instantiated once. But what happens if > > multiple > > > classloaders are used? Such as you have this one class static but > > use it in > > > several web applications? > > > > > > Seems like it MUST reside in common/lib instead of > > webapp/*/web-inf/lib? > > > > > > Hiran > > > > This is where my problem is. I was developing a servlet, which loaded > > a native library and subsequently called some native functions. > > Everything was working fine, but whenever I made changes to the > > servlet and reloaded the application with the manager/relaod call the > > native library was instanciated a second time and crashed. I had to > > stop and restart tomcat in order to see any changes made to the > > servlet. > > > > So I wrote and compiled a class called InitMapserver, which looks like > > that: > > > > public class InitMapserver > > { > > > > static { > > try { > > System.loadLibrary("mapscript"); > > System.err.println("libmapscript.so loaded"); > > } catch (UnsatisfiedLinkError e) { > > System.err.println("libmapscript.so not loaded: " + e); > > } > > } > > > > } > > > > and put it into the common/classes directory. Then I try to load this > > class in a servlet > > doing: > > > > public void init(ServletConfig config) throws ServletException > > { > > try > > { > > Class.forName("InitMapserver"); > > } catch (ClassNotFoundException ex) { > > file://throw new ServletException(ex.getMessage() + "Class > > InitMapserver not found"); > > System.err.println(ex.getMessage() + "Class InitMapserver not > > found"); > > } > > } > > > > Unfortunately this does not work. Any suggestions??? > > > > Thanks > > Andreas > > > > > > > Concerning the JDK documentation a native lib should be loaded > > in a > > > > static > > > > > scope. Static resources are processed differently, because the > > > > runtime > > > > > systems has to initialize all static resources at the beginning. > > > > After that > > > > > the runtime system tries to initialize objects and these objects > > > > can - of > > > > > course - use all static resources. > > > > > > > > > > A look into your code (InitMapserver) shows, that the runtime > > system > > > > cannot > > > > > initialize the static resource in the common way, because it > > first > > > > must > > > > > generate an object and this object contains code for doing some > > > > static > > > > > stuff. Maybe this is the reason for the strange behavior. > > > > > > > > I am sorry, but I am not a skilled Java Programmer and I don't > > quite > > > > understand what you mean. Can you try to explain it more > > explicitly or > > > > give some examples. I hope I am not asking to much.... > > > > > > > > > > -- > > To unsubscribe, e-mail: > > <mailto:[EMAIL PROTECTED]> > > For additional commands, e-mail: > > <mailto:[EMAIL PROTECTED]> > > > > -- > To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> > > > -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
