What is the right way to handle permalinks when th

Question

Here's the situation: I've got an application where you begin at a screen showing a list of countries. You choose a country, and this becomes the ambient country that the application uses until you change it. This ambient country is stored in the Session so the application doesn't have to pass around a CountryId in every single url. But I also want to support permalinks to country specific content, so I guess there needs to be a "Get Permalink" button, which creates a permalink that does contain the CountryId, because it obviously has to work independent of the current session.

Here's the question: My understanding is that because selecting a country changes the session state, one should only do it via POST. But then if the user comes in via GET with a permalink containing, e.g. CountryId=123, what should happen? Should the page update the Session with country 123? In this case, it would be breaking the rule that you can change the session ONLY via POST. But if it doesn't change the session, then all the code that relies on the session won't work, and I'd have to have code redundant ways to generate the page.

OR, should the page have some sort of mechanism for saying "use the session value, but override with any query string value if there is one (and don't modify the session at all)?

OR, am I misunderstanding the POST rule entirely?

Answer 1

The real issue here is the fact that you are using a Session. You cannot provide permalinks because the data that you have stored in the session might have expired when the user follows this links later. So you must somehow persist this data into a more durable datastore when someone requests you to generate a permalink. So when a user asks for a permalink you will go ahead and persist all those search criteria that were used to perform the search into your data store and obtain an unique id that will allow you to fetch them later. Then give the user the following permalink: /controller/search/id where the id represents the unique identifier tat will allow you to fetch the criteria from your data store, perform the search and reconstruct the page as it was.