I guess I wouldn't consider it a bug, but rather a consequence of how classes are loaded and which class loader holds the files in question. But I see your point in that you don't want Hashtable(and more) in all your webapps...
you can open a bug for this and one of the developers(I'm not a developer) will look at it. Feel free to include my responses and I will help best I can. To restate, the classes stored in the Hashtable(and Vector,etc) would have to be in the same classloader as the Hashtable(and Vector,etc) when serializing a class containing a Hashtable. Classloaders can only delegate requests to one 'parent'. So the common classloader either delegates to the 'system' classloader(which it does) or to the 'webapp' classloader(then which one of those?) I guess you would need to provide more detail as to why this would still be a problem for you. Other than having the java classes(Hashtable,etc) in your webapp instead of in the JVM's Bootstrap and having to maintain this with each JVM upgrade, I don't see why this wouldn't work. You *may* be able to move classes that will be in the hashtable to the /jre/lib/ext directory for your JVM, but that's not ideal either as they won't be able to see your other classes loaded by tomcat, but those classes loaded by tomcat will see them. Charlie > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Thursday, August 29, 2002 11:05 AM > To: [EMAIL PROTECTED] > Subject: RE: RE: RE: Problems with class loader > > > Hi Charlie, > > I gave it a try. And guess what: it worked! Now, in this > very simple case > one can argue that adding the collection classes to the > application's lib > directory is not a bad thing to do. But what would one do if > the scenario > wasn't that simple? (Actually, it isn't!) > > Anyway, I consider this still a bug in the classloader hierarchy! > > So, where do we go from here? > > > --- J�rgen > > NB: As for your concerns with loading the classes more than > once: I think > that's what classloaders are for: I would always let it be > their problem... ;-) > > NB(2): Actually, the problem already shows up when an application is > serializing a hashtable that contains an object of a class > that is defined in the > application only. - Yet one reason why I think that's a bug > in the classloader > hierarchy. > > ----------- original post ------------ > > ok, StandardClassLoader means that the class is trying to be > loaded from > \tomcat\lib. If it were being loaded from \web-inf\lib, it would be > WebappClassLoader throwing the error. > > >From your stack trace, it looks as if it is loading the Hashtable > ok(through > reflection), but it is the contents of the hashtable that > can't be loaded. > This would make sense since you put the Hashtable in \tomcat\lib. > > How about if you try to put Hashtable in the \web-inf\lib so > that the first > reflection call will find it in the current(webapp) > classloader, then the > second reflection call(from hashtable) will occur in your webapp's > classloader. Of course being a java class, I'm not sure if it > will have > problems being(or can be) loaded multiple times. > > Charlie > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > > Sent: Friday, August 09, 2002 9:07 AM > > To: [EMAIL PROTECTED] > > Subject: RE: RE: Problems with class loader > > > > > > see intermixed, too > > > > From: [EMAIL PROTECTED] > > To: [EMAIL PROTECTED] > > Date: Fri, 9 Aug 2002 08:42:05 -0400 > > Subject: RE: Problems with class loader > > > > see intermixed > > > > > > > > Hello, > > > > > > we have problems with the tomcat class loaders. > > > > > > scenario: > > > Tomcat 4.0.4, jdk1.3 > > > 2 Applications > > > > > > App1:webapps/App1/WEB-INF/lib/x.jar > > > App2:webapps/App2/WEB-INF/lib/x.jar (the same .jar-file) > > > > > > x.jar: a.class, b.class, c.class > > > > > > b.class has a Hashtable > (com.sun.java.util.collections.Hashtable) as > > > member-variable. (Hashtable is in the directory > > $CATALINA_HOME/lib/). > > > > why is hashtable defined in $CATALINA_HOME/lib ? Is there a > reason why > > allowing the JVM to provide the java classes is a problem? > > This shouldn't > > really matter in this case, but could cause problems keeping > > in sync with > > the current JVM version. > > --> yes, this jar-file doesn't have to defined there but this > > is not the > > problem > > > > > In the Hastable are Objects of the c.class. > > > > > > class a in App1 serialize class b and save it in persistence > > > (poet-)classes > > > in directory ($CATALINA_HOME/lib/). > > so, this poet(I'm not familiar with it) is located in > > $CATALINA_HOME/lib ? > > Is this the class that tries to create an instance of b.class? > > --> no, class a in x.jar tries to create an instance with the > > ObjectInputStream > > > > If so this is your problem. Classes in the /tomcat/lib or > > /common/lib can > > *NOT* see classes in the /web-inf/lib directories. Try > moving x.jar to > > /tomcat/lib and see if it fixes your problem. > > --> I can`t do it because there are dependances to other > > classes in the > > application-directory. > > > > Alternatively you could move poet to each web-inf/lib with > > x.jar, but they > > need to stay together. > > --> this is also impossible because the poet-classes can only > > be loaded from > > one class loader. > > > > j�rgen > > > > Charlie > > > > > In App2 class a load the serialized class from the > > > persistence classes and > > > deserialize it (--> class b). > > > Then, a ClassNotFoundException (class c) is thrown (see > > lower). Why??? > > > > > > class b and the Hashtable are loaded, but not class c. > > > > > > It is as follows: ? > > > The applicationClassLoader finds the class b and then the > > > StandardClassLoader finds the Hashtable and then (however??) the > > > StandardClassLoader try to load class c. And of course the > > > class loader > > > can't find the class c! > > > > > > > > > thanks > > > j�rgen > > > > > > > > > at > > > org.apache.catalina.loader.StandardClassLoader.loadClass(Stand > > > ardClassLoade > > > r.java:1127) > > > at > > > org.apache.catalina.loader.StandardClassLoader.loadClass(Stand > > > ardClassLoade > > > r.java:992) > > > at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313) > > > at java.lang.Class.forName0(Native Method) > > > at java.lang.Class.forName(Class.java:195) > > > at > > java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:654) > > > at > > > java.io.ObjectInputStream.inputClassDescriptor(ObjectInputStre > > > am.java:918) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:366) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:236) > > > at > > java.io.ObjectInputStream.inputObject(ObjectInputStream.java:1186) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:386) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:236) > > > at > > > > > > com.sun.java.util.collections.Hashtable.readObject(Hashtable.java:773) > > > at java.lang.reflect.Method.invoke(Native Method) > > > at > > > java.io.ObjectInputStream.invokeObjectReader(ObjectInputStream > > > .java:2213) > > > at > > java.io.ObjectInputStream.inputObject(ObjectInputStream.java:1410) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:386) > > > at > > > java.io.ObjectInputStream.inputClassFields(ObjectInputStream.j > > > ava:2262) > > > at > > > java.io.ObjectInputStream.defaultReadObject(ObjectInputStream. > > > java:519) > > > at > > java.io.ObjectInputStream.inputObject(ObjectInputStream.java:1411) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:386) > > > at > java.io.ObjectInputStream.readObject(ObjectInputStream.java:236) > > > > > > -- > > > GMX - Die Kommunikationsplattform im Internet. > > > http://www.gmx.net > > > > > > > > > -- > > > 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]> > > > > -- > > GMX - Die Kommunikationsplattform im Internet. > > http://www.gmx.net > > > > > > -- > > 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]> > > -- > GMX - Die Kommunikationsplattform im Internet. > http://www.gmx.net > > > -- > 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]>
