Matthias Noback: Context passing

In a new post to his site Matthias Noback shares some of his recent experience working with a multi-tenant application and the current "contexts" that exist during the user's session. In the most he makes some suggestions about how to generate this context on each request without having to resort to a "data clumping" approach.

In the beginning we start out with a framework that has some authentication functionality built-in. We can get the "current user" from the session, or from some other session-based object. We'll also need the "current company" (or the "current organization") of which the current user is a member.

In the web controller, we take this information out of the session (which we can possibly reach through the "request" object passed to the controller action as an argument). Then we start doing the work; making queries, making changes, sending mails, etc. All on behalf of the current user and the current organization. [...] Soon this starts to feel like a code smell known as a Data Clump: the same data hanging around together.

He offers a few different steps to follow to make sure you're correctly implementing this functionality and not violating the SRP (Single Responsibility Principle):

• Injecting the session
• The Context class
• Passing contextual values on a need-to-know basis
• Fetching more data when needed

For each item on the list there's a paragraph or two explaining the changes and functionality with code examples included where necessary for illustration.