Categorizing Design Patterns

Patterns focus on different types of problems. Related patterns are grouped together and assigned a type. This helps programmers to identify similar types and further it simplifies the process of comparing similar patterns to find the appropriate one(s) to utilize. 

I.  Classification of Design Patterns in general spectrum
    1. Creational Patterns
    2. Structural Patterns
    3. Behavioral Patterns

II. JEE-specific Design Patterns
    1. Presentation tier patterns     
    2. Business tier patterns
    3. Data Access tier patterns

1. Creational Patterns

This design category is all about the class instantiation. Creational pattern uses class-creation patterns and object-creational patterns. The class-creation pattern uses inheritance effectively in the instantiation process while object-creation pattern uses delegation to get the job done. All the creational patterns define the best possible way to instantiate an object. They describes the best way to create the object instances. Many times, nature of the created object changes according to the nature of the program. In such scenarios, we use patterns to give this a more general and flexible approach, for example a object instance can be created using a new operator, which is a hard coding methodology ( hard coding should be the last option to go with).

There are five types of Creational Patterns.
1. Factory Pattern
2. Abstract Factory Pattern
3. Builder Pattern
4. Prototype Pattern
5. Singleton Pattern


2. Structural Patterns

Structural Patterns describe how objects and classes can be combined to form larger structures. The difference between class patterns and object patterns is that class patterns describe abstraction using inheritance and describe how it can be used to provide more useful program interface. Object patterns, on other hand, describe how objects can be associated and composed to form larger, more complex structures.

There are seven structural patterns described. They are as follows:
1. Adapter Pattern
2. Bridge Pattern
3. Composite Pattern
4. Decorator Pattern
5. Facade Pattern
6. Flyweight Pattern
7. Proxy Pattern

3. Behavioral Patterns

Behavioral patterns are those patterns which are specifically concerned with communication (interaction) between the objects. The interactions between the objects should be such that they are talking to each other and still are loosely coupled. The loose coupling is the key to n-tier architectures. In this, the implementations and the client should be loosely coupled in order to avoid hard-coding and dependencies.
The behavioral patterns are:
1. Chain of Resposibility Pattern
2. Command Pattern
3. Interpreter Pattern
4. Iterator Pattern
5. Mediator Pattern
6. Momento Pattern
7. Observer Pattern
8. State Pattern
9. Strategy Pattern
10. Template Pattern
11. Visitor Pattern

II JEE-specific Design  patterns

The term JEE is tossed around a lot because it covers the widest range of applications development in the enterprise and distributed environments. Infact, the JEE modules and environment is still growing with a rapid pace. So, it is important to take advantage of the most efficient and effective strategies while re-factoring the existing projects and developing newer ones. These efficient and effective strategies in JEE scenario are known as the JEE-specific Design patterns.

JEE-specific design patterns identify the minimal set of known problems that application architecture should solve. These patterns are based on the experiences of the JEE community (involved with JEE development) to solve the problems. 
 
 
Classification of JEE Design Patterns :

1. Business Tier Patterns
These business tier patterns tackle problems occuring in an application resulting from the presentation tier accessing distributed business services, network performances degradation due to multiple calls between client and server, memory impact due to retrieval of a large list of data, and so on. The patterns demonstrated here focus on and solve design problems occuring in the middle tier of a J2EE application.
    Session Facade Design Pattern
    Service Locator Design Pattern
    Value List Handler Pattern

2. Presentation Tier Patterns
The presentation tier patterns deal with the common problems occuring in the presentation layer such as - view management and navigation, processing of dynamic business data, efficiently accessing the read-only data, and so on. The patterns under this category focus on and solve design problems occuring in the presentation tier of a J2EE application for example : 
    Fast Lane Reader Pattern

3. Data Access Tier Patterns
These data access tier patterns tackles best practices for an application accessing the database or the underlying persistence layer from the business tier. The patterns demonstrated here focus on and solve design problems occurring in the data tier of a J2EE application.
    Data Access Object Design Pattern