subjunctive mood

If the execute method returns "input" or "error" then the view page rendered would have been hello-input.jsp or hello-error.jsp.

 

这里if条件句用的是一般现在时，而主句用的却是would have been，是基于过去的虚拟语气，它没有用would be，可能条件句是描述一般事实，而主句又不是针对现在的虚拟。