J2EE Design Patterns

Design Patterns

A design pattern is a recurring solution to a recurring problem. From a programming perspective, a pattern provides a set of specific interactions that can be applied to generic objects to solve a known problem. Good patterns strike a balance between the size of the problem they solve and the specificity with which they address the problem.

The simplest patterns may be summed up in no more than a sentence or two. Using a database to store information for a web site is a pattern, albeit a fairly high-level and obvious one. More complex patterns require more explanation, perhaps including the use of modeling languages or a variety of other forms of longer description.

Design patterns originated outside the computer industry, originally showing up in conventional (as opposed to computer systems) architecture. Architects of buildings and architects of software have more in common than one might initially think. Both professions require attention to detail, and each practitioner will see their work collapse around them if they make too many mistakes.

The book to read, if you’re interested in the architectural origins of design patterns, is A Pattern Language: Towns, Buildings, Construction by Christopher Alexander (Oxford University Press). Widespread acceptance of design patterns in software began with the publication of Design Patterns: Elements of Reusable Object Oriented Software (Addison-Wesley), by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, also ...