Bhaskar,
Patterns are, in general, a proven software technique for capturing recurring problems and solving them in a standard way. They reduce time in the development cycle by providing the common terminology and implementation strategy that allows developers to coomunicate the problem and implement it in a reusable fashion. The patterns in the our book are focused on solving recurring security problems in
J2EE and Web Services-based applications. You don't have to use them, but you will most likely end up trying to solve the same problems that they describe. If you choose not use them (or similiar industry patterns), you will just end up re-inventing the wheel. And that may be O.K., depending on your situation. If you want develop software quickly and have it maintained by others, using patterns is a good idea. If you need to sit around and justify time by reinventing solutions, using patterns is not a good idea.