[Tutor] Class in a class

[Kent Johnson]

Liam Clarke wrote:
> Hi Kent, 
> 
> 
>>So the layering is
> 
> 
>>GUI - user interaction
>>Application functionality
>>CbDao - application-specific database access
>>DbAccess - generic database access, easy to use
>>JDBC connection - raw database access, not so easy to use
> 
> 
> This sounds a lot like what I'm aiming for in a project, the layers &
> objects passed up and down, are you able to provide an example of your
> CbDao class for my learning edification?
> 
> (btw, is it Dao as in Lao Tzu?)

The Way that can be known is not the true way. Which makes it hard to provide examples. :-)

Actually DAO stands for Data Access Object which a common pattern for database access, and Lao Tzu's 
version is usually spelled Tao. Though I do appreciate the pun.
http://java.sun.com/blueprints/corej2eepatterns/Patterns/DataAccessObject.html

My CbDao is work code so I can't just post it. It's actually pretty long and ugly too. But the idea 
of it is simple - it includes all of the SQL code of the main application and exposes it as 
application-specific methods. For example my app has a Category object that gets linked into a tree 
and is saved to the database. CbDao has methods like
     def saveCategory(self, category):
     def saveCategoryAsChild(self, category, parent):
     def moveCategory(self, catToMove, newParent, pos):
     def deleteCategory(self, cat):
     def findOneCategory(self, uniqueGroupId, treeId):

The higher levels of the application don't have to worry about the implementation of these methods 
in terms of database operations.

Kent