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Design Patterns

 
Greenhorn
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Doing some simulate tests I notice that the real thing that we need to know about Design Patterns is where we should use each of them. So if someone could give some explanation about these patterns (Value Objects, MVC, Data Access Object, Business Delegate), or at least indicate where I can find any material to study.
[This message has been edited by Samuel Giannotti (edited November 08, 2001).]
[This message has been edited by Samuel Giannotti (edited November 08, 2001).]
 
Ranch Hand
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Hi, you�ll find information about J2EE patterns and links to other resources on the subject at: http://java.sun.com/j2ee/blueprints/design_patterns/index.html
regards.
 
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Hi samuel,
here is a brief understanding of the four design patterns
1)MVC-- When the presentation layer is more than one,i.e a webrowser for the customer, a wml front for the clients and a xml based mapping for the suppliers and retailers.In short when there is requirement of reproducing the same results across more than one medium
2)DAO- when the data storage is likely to change quite often,(no persistent data store) or there is no fixed medium for your application data, could be a Oracle,Sybase, or a LDAP, a flat file etc.. and you need to shield ur buiness logic from the data
storage.
3)Buisness delegate: when there is a requirement to shield the presentation layer from the buisness logic .i.e if your presentation layer is dependent on ur buiness layer, and it gets affected.
4)Value Object: When there is a reqirement to retrieve values of different properties remotely in a distributed framework one has to make a lot of calls and that is an overhead in terms of network connection, so there is one call made to the EJB which collects all the values and returns you back.
hope this helps....
 
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