Component Diagrams by Mark Cade

[Lukas Moser]

The component diagrams in the case study, chapter 8 (Sun Certified Enterprise Architect for J2EE Technology) by Mark Cade look rather simple.
E.g. they do not use any EntityBeans at all. Instead, DAOs are used.

Of the well known presentation tier patterns only a controller is used. Intercepting Filter, View Helper etc are not used.

Is it possible to pass the assignment in this way.
Is there anybody who passed with very similar component diagrams?

[Pham Huy Anh]

Hello,

I am thinking about component diagram. And I have larger concern. Many books said :"A component is a named physical and replaceable part of a system" and that the component is represented by interface(s).
- I think Intercepting Filter, View Helper are part of Web component, is that right?
- Should we show JSP/Servlet part on component diagram?
- Is that Web component?
- Could we consider Web component as normal component?

Thanks,

[Awais Bajwa]

I am thinking about component diagram. And I have larger concern. Many books said :"A component is a named physical and replaceable part of a system" and that the component is represented by interface(s).
- I think Intercepting Filter, View Helper are part of Web component, is that right?
- Should we show JSP/Servlet part on component diagram?
- Is that Web component?
- Could we consider Web component as normal component?
Thanks,

In raw form, any independent module or group of objects that can be plugged to any system is a component. All components must need to define an interface or a set of interfaces, no component can live in isolation. Intercepting filter sounds like a component, as it can be associated to any servlet container, i m not sure what a view helper is.
We can show any JSP/Servlet as a part of component diagram for sure, web component can be supposed as a normal component as far as they satisfy the component agreement.

A.B

[Pham Huy Anh]

In raw form, any independent module or group of objects that can be plugged to any system is a component

==> Agree. And I quote from Developing Enterprise Java Applications with J2EE and UML

Components that perform specific tasks can be bought and sold. These can be
assembled together into larger applications. This reduces time to market, overall resource requirements, expertise required, and so on.

But a component have dependencies on other components. A depends on B, C, D... I think component A can't work well in new system without B and/or C... Please explain to me?

Moreover, component in Java may be expressed as an JAR file, right?
Can I consider struts.jar as a component!?

Thanks

[Frank Kuepper]

Hi Lukas,

Originally posted by Lukas Moser:
E.g. they do not use any EntityBeans at all. Instead, DAOs are used.

Of the well known presentation tier patterns only a controller is used. Intercepting Filter, View Helper etc are not used.

Is it possible to pass the assignment in this way.

I don't know Cade's book, so I can not judge his diagrams.

But remember, that architecturing is not simply combining a bunch of common patterns. The fact, that a pattern exists, does not mean, that is to be used in all cases ;-)

It's all up to the architect to decide, which patterns to use, and to justify that decision. Consider, that it is sometimes better not to use a pattern than to use it, because all patterns - besides their benefits - also introduce drawbacks.

And the same goes for the use of EntityBeans and DAO - it's up to you and the justification of your choice.

Just my 2 cents...
Frank

[Marc Peabody]

Originally posted by Lukas Moser:
Of the well known presentation tier patterns only a controller is used. Intercepting Filter, View Helper etc are not used.[/b]

I have not viewed them in a while, but I recall that Cade's component diagrams have no presentation tier patterns. If he called something a "controller", the closest J2EE pattern to his intentions would be a Session Facade, which is a business tier pattern.

Additionally, if I were scoring the submissions and someone included something like an Intercepting Filter without an incredibly darn good reason for it, I would knock off a significant amount of points.

[Marc Peabody]

I stand corrected. I see that Cade's component diagrams include a servlet labeled as a Controller and 4 JSP components interfacing with it.

[Frank Kuepper]

Originally posted by Marc Peabody:

Additionally, if I were scoring the submissions and someone included something like an Intercepting Filter without an incredibly darn good reason for it, I would knock off a significant amount of points.

Totally agree with you, Marc! I constantly have to fight unexperienced co-workers going "pattern crazy" with no reason Architects have to know better