Why does sbt fail with NoClassDefFoundError: play/Play$ in Play 2.2.x projects after sbt compile in Play 2.3 project?
问题 Once I run 'sbt compile' on a 2.3 play project, I can't use 'sbt compile' to compile any Play 2.2.x projects anymore. This is the error when I run sbt command. [info] Loading project definition from /Users/macbookpro/playproject/project [error] java.lang.NoClassDefFoundError: play/Play$ [error] Use 'last' for the full log. Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? 回答1: I just had this same issue. In my case I was using Play 2.4, but it's probably the same cause. I had run