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Data Access Object & Value Object

 
Johny Sam
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What design pattern does the Data Access Object & Value Object match to?
Can some one help !
 
JeanLouis Marechaux
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Data Access Object (DAO) is used to encapsulate all data access (RDMS, OOMS, LDAP, XML...) in 1 object.
For instance, if your data are in a RDB, all the SQL code (select, update, delate) is within a DAO, and your application have to use this DAO in order to perform a db access
Many advantages... let's say, more OO, better for scalability (if you change the data from a DB to a LDAP just need to change the DAO accordingly ), easier to migrate from BMP to CMP etc..

A value object is a java class which represents data from the DB and is accessible without RMI calls.
When you perform a DB read, you store the result in Value objects. Each value object is loaded in memory and is available for futur calls.
Hope this is clear.
 
Jun Hong
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Hi there,
In fact, DAO and VA are core J2EE design patterns. These patterns are mentioned at javasoft web site. Also, there is a book core J2EE Patterns.
 
Johny Sam
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Thank you so much for clearing my doubts with DAO &VO.
 
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