You want to create templates for your Java based backend that runs your current site(s)? Is that what you are looking to do?
If that is the case then you want to use Pinegrow to import your pages directly from your live site and edit them in the program. Save them out and then replace the sections that were generated by your markup with the actual markup tags you need. Then upload these page(s) back to your site.
I use a custom CMS written in PHP and this is the process I go through with Pinegrow to create my templates or themes. Working directly in Pinegrow as an IDE is not really it’s purpose. It is more like Dreamweaver without the direct server connection stuff. You design the pretty with Pinegrow then in your IDE or whatever you use to code with, you tear the page apart and make your template with the markup you need.
The only CMS that Pinegrow works natively with is Wordpress and you need that special version of Pinegrow to do it right.
I would not want to use Pinegrow as a code editor, even with the changes coming in the next release. The reason I ended up buying the Pro version of Pinegrow was to easily create the final look and feel of my pages, the HTML and CSS without having to manually code everything from scratch.