Subtlety in WebappClassLoader wrt to leading '/'

[Aaron Hamid <ar...@cornell.edu>]

Hi all,

  I have searched bugzilla, and the tc-users and tc-dev lists on MARC, as well as the source code, so hopefully this is vetted enough for this list (I have NOT posted a bug).

It appears that WebappClassLoader (in at least versions 5.0.28 and 5.5.12 which I have looked at) will accept a leading slash '/' on the resource path parameter to the 'getResource*()' calls.  This implicit support appears to be due to the File and URI/URL APIs it uses to resolve the resource.

While it is intuitive to me to support a leading slash, Sun's application class loader behavior is different.  Resource paths with leading slashes are not found.  When the slash is removed they are found.  I could not find any mention of these semantics in the standard ClassLoader (not Class, I am aware of how Class.getResource differs) documentation, however a quick Google search will confirm the notion that ClassLoader will not find resources with leading slashes (at least one old post on tomcat-dev: http://mail-archives.apache.org/mod_mbox/tomcat-dev/200108.mbox/%3C3B7854FF.2FA71171@apache.org%3E quote at bottom).

I raise this issue because I just spent a lot of time debugging a problem where a certain resource WAS found in Tomcat, but was not found when running JUnit tests from Ant or from within Eclipse.  Ultimately it was my fault for prepending a slash, but I wonder if it is worth either matching Sun's behavior, or documenting this somewhere (and again, I may have missed it).

Aaron Hamid
CIT/ATA
Cornell University

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