Modifying the static file before Shelf handler returns it

[David Notik]

Hi! I'm trying to replace a string in my index.html (which is my SPA) with another string.

It's for this issue (basically trying to inject user object server-side): http://stackoverflow.com/questions/34883984/can-i-avoid-round-trip-to-get-user-for-session-on-spa-load?noredirect=1#comment57506409_34883984

Shelf serves my index.html with the shelf_static lib:

final shelf.Handler staticHandler = shelf_static.createStaticHandler(
 config['server']['directory'],
 defaultDocument: 'index.html',
 serveFilesOutsidePath: true);

...

static serveApp(App app, shelf.Request request, [String path]) {
  return app.staticHandler(
      new shelf.Request('GET', Uri.parse(app.serverPath + '/')));
}

Where/how might you recommend I modify the returned index.html? Read the file in as string, replace, then return it back? So then don't use shelf_static?

--D

[Natalie Weizenbaum]

You probably don't want to entirely avoid using shelf_static, since it has a bunch of nice caching logic that would be a pain to re-implement. I'd suggest you write a simple piece of middleware that detects responses to GET /index.html, reads in the response body, does the search-and-replace, and then uses Response.change() to return an updated response.

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[Anders Holmgren]

I suspect that most use cases for variable substitution are cases where the response may change per request (e.g. per user) and shouldn't be cached. For such caches a template engine like mustache is likely a better fit

[David Notik]

Makes sense to me. Natalie would you concur?

[Natalie Weizenbaum]

Sure. A clever template engine handler may even be able to cache based on a combination of template age and variable identity.

[David Notik]

Sure! It'd be a tiny improvement given my little change to the file contents. For now, injecting my user data into the file gave me a little server-side magic and substantially improved the load times for my Polymer SPA. (I was waiting until hasTriedLoadingUser, which was round-trip, before.) Woot!

ᐧ

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http://woven.co
206-351-3948

@DaveNotik