The Data Reflection pattern is a pattern that keeps web application content in sync with the database and with the file it is requesting. This pattern can be used in a number of ways. In our sample, it will be used as a way to keep a user's email data current by allowing the application to receive new emails from other users. This means that if a user sends email to another user, the receiving user will get this new email whenever the data happens to be reflected in the back end of the application. This reflection will be based on a delay or time interval that we set in the code. Or, the functionality could also be extended into a user preference, which would allow a user to choose how long a delay he has for email checking, such as current desktop applications have. The limits are based on your application and what pieces of it could benefit from using this pattern because it provides niche functionality that is not always going to be necessary.
In this chapter, we will learn different ways this pattern can be useful in a web application, as well as specific sections of an application that might benefit from it.