• Post Reply
  • Bookmark Topic Watch Topic
  • New Topic

DAO vs. entity EJB; Definition of "component"

 
Thomas Taeger
Ranch Hand
Posts: 311
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hello Saha,
I made my answer a new thread for giving it a meaningfull topic name.
Originally posted by Saha Kumar:
In another post, you said you would not put a DAO and a BMP entity together in the same component?

Are you questioning what could be packed together in a component? In UML-2 this is much clearer now. Not just "the EJB". As you know you can specify an "artifacts" compartment for the name of the physical .jar including a deployment descriptor, so today you have a better chance to think in imaginable things. In UML-1 the whole component had been seen as physical.

Or are you questioning the role of entity-EJB vs. DAO? Both access the database. You design either an entity EJB or a DAO for one given table [and sub-tables in 1.1]. I remember some people arguing to hide "technology specific" entity EJBs behind DAOs but still getting the benefits (caching, transactions) of the container.

Originally posted by Saha Kumar:
If the DAO was not to be used anywhere else, wouldn't this be considered dependent?

Also here: Dependent of what?

I try to guess your question:
For entity EJB:The EJB along with its deployment constructor is a pluggable, replacable, deployable component, and needs to be due to be ruled by the container. It provides an interface, may depend on any prepackaged sub-jars but also may be totally independent from any other component because not having any required interface.

For DAO: I can not remember having seen a single DAO forming a component, i.e. with an own deployment descriptor in the .jar of the DAO. That could make sense for ease of replacement by other DB-accessing/OR-mapping technologies like EJB-3 later - provided the DAO has a clear interface that later can just be realized by another component.

Thomas
[ May 12, 2006: Message edited by: Thomas Taeger ]
 
Saha Kumar
Ranch Hand
Posts: 218
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hello All,

I am using UML 2.0 white box component diagram. I want to show a composite entity as a component. The composite entity contains dependent POJOs and an entity EJB.(http://java.sun.com/blueprints/corej2eepatterns/Patterns/CompositeEntity.html).

I want to know if the white box component diagram allows other components to be included in the diagram (i.e. I only see java classes which are used internally by the component).

Thanks in advance.

-Saha
 
Saha Kumar
Ranch Hand
Posts: 218
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hello All,

I think I found the answer for anyone working with UML 2.0 white box components. I found

The graphical notation for a UML 2.0 Component is either a "black box" view to only show the interfaces, or a "white box" view to show the internal assembly of subcomponents if any (parts or classifiers). The component logo can be associated or replace the <<component>> keyword.


and also

that a classifier in UML 2.0 includes:

..., class, component, ...


So I think its safe to conclude that a white box component in uml 2.0 can contain other components.

references:

web page

web page

-Saha
 
Thomas Taeger
Ranch Hand
Posts: 311
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
What is going wrong?

You had a question. I took the time to answer. You just ignore it and abuse this thread for posting another question instead.

If you need a coach in this manner you should rent one outside of forums.

Please for new questions open a new thread.
 
Saha Kumar
Ranch Hand
Posts: 218
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thomas,

Thanks for the insite from your posting. I have answered my question and also see your points.

-Saha
 
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic