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From "Remy Maucherat" <>
Subject Re: Class Loader Triggers
Date Thu, 28 Feb 2002 03:56:58 GMT
> Shouldn't the servlet.jar file be placed on the system classpath by the
> startup scripts?  The servlet container itself supports a specific version
> of the servlet API and the web applications should not be able to pick and
> choose which version they wish to use.  Placing these classes on the
> classpath (along with changing the class/resource loading algorithm) would
> fix this, because webapps would check the system classloader first.

There are some tricks which can be used to put some JARs in the system
classpath (for example, Xerces), but it's not a robust solution and would
break if the user decides it wants to use JAXP 1.2 instead (or just renames
the JARs). So I don't think we should use that kind of solution.
With servlet.jar, it's even harder to do, because of Jasper, which uses
filesystem based compilation, and which would cause compilation errors if
the webapps repositories contained some older version of the servlet API
(the trigger for the Servlet class in the WebappClassLoader avoids this, but
at a price). Note: This was the most often reported user error.

The upcoming 4.0.3 b1 (coming tomorrow or friday; or you can try one of the
nightly builds) will provide a nice compromise, with non intrusive class
filtering, while allowing you to put almost anything you want in the webapp


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