why I cannot convert an existing Eclipse project to the dynamic web project?

I have an开发者_如何学Python existing Eclipse java project, and need to export it to the war file for deployment. By googling, it turns out that I need to covert it to a dynamic web project at first. But the menu item for this conversion is disabled. I would like to know why.

You want to edit the project properties and go to project facets. In there you can select the Dynamic Web Module facet.

you need to select the Dynamic Web Module as mut1na said and the java server faces box if you're importing a jsf project. You will probably need to check the runtime too.