Pages Cached By The Cache Manifest Do Not Need To Reference The Cache Manifest

In last night's post, I discovered that non-cached pages could not make use of resources cached within the application cache. As I was experimenting with that concept, I found that when I added a cache manifest reference to the non-cached page, it both became cached and was granted access to the other cached resources. This is, of course, the expected behavior and exactly what I covered in an earlier cache manifest exploration; but, the question then rose in my mind: is it the cached status or the cache manifest reference that gives one page access to other resources stored in the application cache?

After some quick testing, the answer to this question is: cached pages do have access to the entire set of cached resources regardless of whether or not the given page makes any reference to the cache manifest. In other words, it doesn't matter how a page gets cached; but once it does, it has full access to the offline application cache.

To test this, I took yesterday's experiment and simply added the main testing page (index.cfm) to the cache manifest file. Then, as before, I had the "cacher" page reference the cache manifest while the main page remained a standard HTML page:

Cache Manifest (cache_manifest.cfm)

As you can see, all I did here was add the "index.cfm" relative URL as a line item within the cache manifest. Then, I had the "cacher" page link to this cache manifest:

Cacher (cacher.cfm)

Again, the only job of this page was to make a reference to the cache manifest such that the server would create the offline application cache and proceed to cache each file listed in the manifest. I needed to create this cache by proxy since I wanted to see whether or not the cache manifest reference was required in the main page (index.cfm).

Once I had my cache manifest and my "cacher" page set up, the main page was able to remain as-is:

Main Page (index.cfm)

As you can see, while this page has an HTML5 doc type, it makes no reference to the cache manifest. In fact, this page is not even cached until I execute the "cacher" page which initializes and populates the offline cache. However, once the "cacher" page is requested, and the cache is created, this main page is able to successfully access the images stored in the offline cache.

So, based on last nights post, we can see that non-cached pages cannot access resources in the offline cache; however, once a page does become cached, regardless of the means by which it became cached (through direct reference or by proxy), that cached page then has access to entire offline application cache. Again, this is something that might be pretty obvious; but when you live in the client-server world, the concept of persisted client caching raises a lot of questions!

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