Patterns & Platforms: Deprecated Patterns?

Let's say you have used a pattern many times in your implementations. And then
one day something new comes along and you no longer need to implement that old
pattern anymore. So what happens to that pattern? Does it get deprecated? I
have come across this question many times while talking to other developers.

For instance, this question of pattern deprecation is associated with some
patterns we documented in Core J2EE
. We first released these patterns in the 1st edition. And when
newer version of J2EE/EJB/Servlet specifications became available, these patterns
gained direct support in the underlying platform. The questions related to a
few of the J2EE patterns are:

  • Did Intercepting Filter pattern get deprecated since Servlet version 2.3 specification introduced an new Filter component ?
  • Is Composite Entity pattern no longer applicable since EJB 2.0 introduced local EJBs?
  • Is Service Activator pattern deprecated since EJB version 2.0 introduced Message Driven Beans (MDB)?

IMO, patterns do not get deprecated. In these cases above, the patterns were absorbed and supported into the relevant specifications. This makes the platform better because it is providing built-in support for well known patterns. So as platforms mature, some platform patterns can get assimilated into the platform as a process of improvement.

This process however does not diminish the value of those patterns. Instead the forces around the patterns can change a bit leading to new solutions and strategies for implementing the pattern in the new platform. This is what happened to some patterns in Core J2EE Patterns. As J2EE evolved, the strategies we describe for these patterns also evolved. I look at this as a process of symbiosis and maturation between patterns and platforms.



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