Classes in /common and /shared can not see classes in /WEB-INF. A class loaded by the nth classloader will not see any classes loaded by (n-1) classloader. However, it will see classes loaded by n+1 loader. This is the classloader hierarchy. Any classloader only has one parent to which it can delegate any classes that it can not resolve. Since multiple classloaders(one for each webapp) can have the same parent, the common classloader would not know which "WEB-INF" to reference when searching for a class.
Therefore all your classes need to be in /common if any within /common reference them. As an alternate, you can copy all classes to each /WEB-INF. Charlie > -----Original Message----- > From: Larry Levin [mailto:[EMAIL PROTECTED] > Sent: Friday, June 25, 2004 9:30 AM > To: [EMAIL PROTECTED] > Subject: class loader interdependencies > > Hi all; > > I am trying to share some jars across multiple web-apps, each of which > runs in its own environment (i.e, JVM). To do this I make use of the > CATALINA_BASE environment variable. My problem is in regards to class > loading. > > I have a number of jar files that are common to each webapp but I also > have a couple that are unique to each app. According to the > documentation for Tomcat 4.1: "from the perspective of a web > application, class or resource loading looks in the following > repositories, in this order:" > > 1) /WEB-INF/classes of your web application > 2) /WEB-INF/lib/*.jar of your web application > 3) Bootstrap classes of your JVM > 4) System class loader classes > 5) $CATALINA_HOME/common/classes > 6) $CATALINA_HOME/common/endorsed/*.jar > 7) $CATALINA_HOME/common/lib/*.jar > 8) $CATALINA_BASE/shared/classes > 9) $CATALINA_BASE/shared/lib/*.jar > > I have therefore tried two different approaches, both of which fail for > the same reason. > > 1st approach: I modified the standard startup script to add the shared > jars to the CLASSPATH, thereby treating them as System class loader > classes (i.e., category #4 in the above sequence). > > 2nd approach: I placed the shared jars in $CATALINA_HOME/common/lib > (i.e., category #7 in the above sequence). > > In both cases everything works fine UNTIL one of these shared classes > needs to access a class located in one of the /WEB-INF/lib/*.jar of a > web application (i.e., category #2). At that point my code throws a > ClassNotFoundException. > > My impression is that something in the class loader procedures prevents > "loading backwards" by which I mean: > > IF Class X was loaded by the nth loader in the sequence (e.g., #4, > the system loader), > AND Class X references a previously unloaded class, > THEN Tomcat will ignore any loader lower in the sequence the > Class X's loader > (e.g., loaders 1-3 (the /WEB-INF and bootstrap loaders > in this example)) > when attempting to resolve the reference. > > Is this a correct assumption and does anyone have a suggestion for > working around this "feature"? > > Thanks > > Larry > > > > > > -- > > Lawrence J Levin > Critical Architectures, LLC > Skillman NJ 08558 > email: [EMAIL PROTECTED] > voice: (609) 333-9750 > cell: (908) 227-8485 > fax: (609) 333-9751 > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED]
