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MVC August 19, 2005

Posted by Coolguy in Software Design.
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  • The essence of MVC is that you separate the business logic from the presentation and put something in between them so that the business logic can stand on its own as a reusable java class and doesn’t have t0 know anything about the view
  • MVC takes the business logic out of the servlet and puts it in a model – a reusable plain old java class.
  • The model is a combination of the business data and rules that operate on the data.
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Classifying patterns July 22, 2005

Posted by Coolguy in Software Design.
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The authors divided these patterns into three types:

Creational,

Structural

Behavioral.

Creational patterns are ones that create objects for you, rather than

having you instantiate objects directly. This gives your program more flexibility in deciding which objects need to be created for a given case. This often involves isolating the details of object creation so your code isn’t dependent on what types of objects there are and thus doesn’t have to be changed when you add a new type of object. Singleton,Factory Method,Prototype are classified as a creational patterns

Structural patterns help you compose groups of objects into larger structures, such as complex user interfaces or accounting data. This invloves designing objects to satisfy particular project constraints. These work with the way objects are connected with other objects to ensure that changes in the system don’t require changes to those connections.

Behavioral patterns help you define the communication between objects in your system and how the flow is controlled in a complex program. These encapsulate processes that you want to perform, such as interpreting a language, fulfilling a request, moving through a sequence (as in an iterator), or implementing an algorithm.Observer and the Visitor patterns are common examples.

What is a pattern? July 22, 2005

Posted by Coolguy in Software Design.
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You can think of a pattern as an especially clever and insightful way of solving a particular class of problems. That is, it looks like a lot of people have worked out all the angles of a problem and have come up with the most general, flexible solution for it. The problem could be one you have seen and solved before, but your solution probably didn’t have the kind of completeness you’ll see embodied in a pattern.

How many design patterns? July 22, 2005

Posted by Coolguy in Software Design.
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The 23 design patterns selected for inclusion in the original Design

Patterns book were ones which had several known applications and which

were on a middle level of generality, where they could easily cross

application areas and encompass several objects.

Do I have to use the design pattern? July 22, 2005

Posted by Coolguy in Software Design.
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If you want to be a professional Java developer, you should know at least some popular solutions to coding problems. Such solutions have been proved efficient and effective by the experienced developers. These solutions are described as so-called design patterns.

Defining Design Patterns: July 22, 2005

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Design patterns are recurring solutions to design problems you see over and over.

The design patterns are language-independent strategies for solving common object-oriented design problems.

Design patterns help you learn from others’ successes instead of your own failures.