Erik Brakkee

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since Jun 21, 2004
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Recent posts by Erik Brakkee

Hi Munwar,


As with many of the CMSes it is often difficult to start to learn them.

Therefore, I have the following questions:
* is there a well-defined model to define pages? Is it based on templating?
Is the template fixed for all pages or can it easily be changed?
* What knowledge do I need to have if I want to write a custom component
for Alfresco? Do I need to know JSR-170, Hibernate, JSF, XSLT, or proprietary API of Alfresco? What tools does Alfresco provide to support development of add-ons?

Cheers
Erik
13 years ago
Hi,


Just for completeness, www.certmanager.net/~sun shows the status pending after completing part III and www.certmanager.net/sun_assignment does not show anything (in my case).

Cheers
Erik
Hi,


What I am doing is to include a section on the UML modeling conventions I use. This is basically a collection of how I model many situations in a simplified form. Since the complete form can always be derived straight from the simplified form, I can simplify the modeling in the sequence diagrams.

As far as call and return parameters are concerned, I am using names whereever appropriate, for instance to show that the result of one call is input to another call I name the return and call parameters. I just show enough to understand the general concept.

Also, I include text to explain the sequence diagrams. I am assuming that those people who are grading the exams are sensible people.

Cheers
Erik
Hi,


I am just using UML 2.0. It's the only version my tool (magicdraw) supports, and I haven't seen any mention of the UML version to use. I think you can choose it just like the J2EE version.

Cheers
Erik
Hi Roger,

Unfortunately, I am not well versed enough on EJB 3.0 to use that one in the assignment. I am just going for EJB 2.1. I am leaving EJB 3.0 for some later time.

Off topic:
By the way, with EJB 3.0, will my entity beans be concrete classes instead of abstract? Can I test my EJB 3.0 entity beans with CMR in a standalone environment or do I still need to use a container to test them?

Cheers
Erik
Hi,

This is one of the very frequently asked questions.
Part I of the exam is about EJB 1.1.

So take your time machine and go back in time.

Cheers
Erik
Hi Karim,


I didn't actually read anywhere that this was possible, but could find any place that said it wasn't. Anyway, your reply clarifies a lot.

Thanks
Erik
Hi Roger,


You understand exactly what I mean.

As for the reasons to use wrap CMP entity beans with DAOs. There are many:
  • It makes your code independent on J2EE and thus also testable outside

  • of an application server which is a huge advantage. Also, it provides
    a huge simplification of the domain model since it does not have
    to deal with the intricacies of entity beans.
  • It decouples the development of your domain model from that of the

  • database. In particular you can use an assembler to map a fine grain
    domain model to a coarse grain model of entity beans.
  • It provides more freedom in the design of your domain model. In

  • particular, simple things in a regular POJO domain moasidel such as
    inheritance are difficult with entity beans.

    I think I am going for a design with DAO + CMP for these reasons because I am using inheritance in my domain model. Looking on the internet for some tricks to see how to implement inheritance with entity beans, it is apparent that this is possible, but increases complexity, and in my opinion increases it too much.

    By the way, I think there is growing consensus these days that entity beans are one of the shortcomings of J2EE. At work we are doing all new development using DAOs and Hibernate. DAO to be independent of the persistence mechanism and Hibernate for obtaining the easy mapping of a fine grain object model to a coarse grain data model, and to allow persistence also to be used outside of the container.

    Doing the certification feels a bit like selling my soul, but it is possible to do a proper design with entity beans as well. If inheritance would have been easier with entity beans, then I could have simplified my submission by using CMP entity beans directly. Now because of these shortcomings, I have to introduce DAOs because otherwise the code would get too complex for my taste.

    Cheers
    Erik
    Hi,


    I have been reading about CMR and there is one question I could not find an explicit answer to and this is how to support relations between CMP and BMP entity beans. As I can see it there are no restrictions here so any of the following is possible:
    1. a uni-directional relation from a CMP to a BMP entity bean
    2. a uni-directional relation from a BMP to a CMP entity bean
    3. a bi-directional relation between a CMP and BMP entity bean
    Of course, also in all variants: one-to-one, one-to-many, many-to-one, many-to-many.

    Can anyone confirm this?

    Cheers
    Erik
    Hi,


    Almost right. The home interface of my entity bean will be almost the same as the DAO interface, except that the DAO interface does not extend EJBHome.

    But, although I would go for such a design in practice, to make it more J2EE independent, I will probably just go for CMP entity beans for the assignment as is to keep things simple for SUN and to increase my chances of succeeding.

    Cheers
    Erik
    Hi,


    I am thinking of drawing packages on class and component diagrams to group classes and components. This is in my opinion, more clear than showing a separate package diagram. It is also UML compliant since UML does not limit the elements that can be drawn on a specific diagram (see last sentence of appendix A, UML user guide, Booch et.al.).

    This is all nice, but would this give a problem when I submit my assignment?
    Does anyone have any experiences with this?

    Cheers
    Erik
    Hi James,


    In many cases, collection return values can be modeled as arrays. Then, you explain in your assignment that you use the convention to model collections as arrays. During development, the actual implementation can then be chosen (array, list, set).

    Cheers
    Erik
    Hi,


    I don't know of any 'standard' for modeling J2EE components in UML, but what I do is to define stereotypes (e.g. <<StatelessSessionBean>> and add them to the classes/components I create.

    One really good book about UML that I like is 'The Unified Modeling Language User Guide by Grady Booch et.al'.

    Cheers
    Erik
    Hi James,


    My absolute all-time favorite is magicdraw UML. There is a free edition which is probably too limited for the assignment, but you can also get demo licenses that work for a few months. Perhaps they can give you a longer tryout period if you say you are using it for your SCEA assignment (suggesting of course that you would recommend it to your boss to use at work).

    Cheers
    Erik