Caldarale, Charles R schrieb am 24.11.2008 um 21:51:33 (-0600): > > From: Michael Ludwig [mailto:[EMAIL PROTECTED] > > > Could web app Foo, which brings its own DB2 driver - in spite > > of the same driver already offered by the common.loader or > > the bootstrap.loader, by this very fact jeopardize other web > > applications running in the same container, which rely on the > > DB2 driver offered by the "common.loader"? > > > > Or would web app Foo only harm itself? > > If an object originating in a webapp classloader is passed to code > from a more global classloader, and then another webapp accesses that > object, it will not be castable to any type the second webapp has > access to. (Class myPackage.MyClass loaded by classloader A is not the > same type as myPackage.MyClass loaded by classloader B.)
That's an interesting fact, and good to know. The very fact that object leak from one web app into another is a possibility seems to constitute a strong argument in favour of strict monitoring, be it only to shield oneself from errors that might be difficult to track down. > > Does this mean web apps have to be monitored for the classes they > > make available in order to make sure none of them has already been > > made available via the common.loader? > > If a webapp minds its own business, there shouldn't be a problem. If > it tries to use Tomcat's DB connection pooling (or logging, or some > other shared mechanism), but insists on providing its own copy of the > shared classes, then there are likely to be problems. (This is a > problem with servlet containers - not just Tomcat - because it breaks > the standard Java classloading model of always delegating upwards. As > mentioned before, this breaking is pretty much required by the servlet > spec.) May I rephrase this into there being a duty for the Tomcat admin to enforce none of the web apps loaded into his container supply a library that the container itself already supplies? Michael Ludwig --------------------------------------------------------------------- To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
