自省或操纵Freemarker模板

Question

I am working with "dynamic" Freemarker templates, meaning templates that can change based on user-submitted input. I would like to be able to do 2 things:

1. Inspect the parsed syntax tree of a template to see what it contains, especially identifiers and ${variables}.
2. Manipulate that parsed tree, adding/removing elements.

Right now, I'm accomplishing this with some ugly regex and string manipulations. It's ugly and error prone, so I'd love to take advantage of Freemarker's template representation in Java.

According to the JavaDoc, Template.getRootTreeNode seems to be the beginning of what I want: I can retrieved a DOM-like parse tree of a template, an instance of TemplateElement. But many concrete implementations of TemplateElement are not public. The JavaDoc doesn't even document TemplateElement. It appears the only way I can get useful information from a TemplateElement is to write code that lives in the Freemarker package. Is there a Freemarker-blessed way to inspect a template?

Ideally, we'd have proper documentation of the TemplateElement hierarchy and make its subclasses public. While that won't let me directly modify the template, at least that would let me inspect the template's elements.

The following question was also asked a few years ago, with limited results:

How can I introspect a freemarker template to find out what variables it uses?

Update :

I have started a Github open source project to enable introspection of the parsed Freemarker template, to allow the kind of programmatic analysis and manipulation I discussed above. Feedback is welcome:

freemarker-introspection

Answer 1

FreeMarker currently doesn't have a published API for inspecting templates, let alone modifying them. It would be useful, but it just doesn't have it. So, I wonder if you can attack the problem from a different angle. You say you are generating templates dynamically, and unless the templates themselves are user-submitted, you could store the user-submitted information based on which you generate the template, rather than the template itself... or something like that.