In the middle of the Tomcat 5 installation, MacPorts was unable to download the required version of antlr, 2.7.7. After a bit of digging, it became clear that this was because the antlr website only has the latest versions available for download.

The required version of antlr is available in the gentoo distribution, so you can get around the problem.

  1. Download antlr-2.7.7.tar.gz from gentoo or I mirror. I got it from Planet Mirror.
  2. Edit the antlr portfile (by default it's at /opt/local/var/db/dports/sources/
    rsync.rsync.darwinports.org_dpupdate_dports/lang/antlr/Portfile (line split for readability)). You need to change master_sites to the location of the antlr source you downloaded, for example file:///Users/michael/Desktop/.
  3. Run port install tomcat5, and all should be well.