I have seen some comments around the interwebs about ColdFusion 8 application specific mappings solving the problem of using frameworks in shared hosting environments and in environments where global mapping is discouraged. I know that I have come across at least one situation where this is not the case, and I though I would share.
Don't get me wrong, I think application specific mappings are wonderful, and the commenters are mostly right in what they say, in MOST cases, application specific mappings will make hosting in a shared environment much easier.
Firstly, one caveat to having Application Specific Mapping on your shared host is for them to allow it. Of course, the advice here is, if they won't allow it, go elsewhere. There are plenty of other hosts out there that will allow it.
The second issue can be seen in this little snippet from Application.cfc on a standard Mach-II site.
<cfcomponent displayname="Application" extends="MachII.mach-ii" output="false">
If you see the problem, raise your hand.
Of course, the problem is, the Application.cfc is Extending MachII.mach-ii before we are able to declare the mapping for MachII. This means that any existing mapping would override our and it would mean that if the MachII folder was not at the root level of the site, that the application would not be able to find it at all.
There are two solutions to this, the first being to move MachII to the webroot. The second option is to create a server side mapping. Now to be a good Shared Hosting Neighbor, you do not want to create a global mapping called MachII, since others on the server are probably using a different version of MachII than you. So you should create a server-side mapping with a unique name. For example, I would place my MachII folder in c:\wwwroot\MyFrameworks\Robot\. Then I would have my host create a mapping called "/robot".
Now, I can extend robot.MachII.mach-ii and then create my application specific mapping to "/MachII", using the same copy of MachII, for the rest of the app to use.