How to do Java 5 on the Mac?

I've installed Java 5 in the past on the Mac from a site I found, but as soon as Apple pushes another Java 6 version, it wipes out my carefully-installed Java 5.

I do not understand why Apple will not let me manage my own Java installations (or at least leave the existing installation alone or ask me if I want to remove it)?

The problem I often run into is if I compile a Java file on the Mac and try to deploy it to Tomcat where the application uses Java 5, I get a "bad class number found in file" or similar exception.

Is there a workaround to this problem without recompiling the entire application in Java 6?

Thanks.

- M