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Java Forum / First Aid / March 2005

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from j2sdk to j2ee ?

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Dado - 19 Mar 2005 22:53 GMT
Until today I developed, small but usefull, desktop applications, using
j2sdk. Now, I'm thinking about developing a web appllication.
When I started learning java, I was thinking that the natural progress is
from j2sdk to j2ee, but somewhere I red that it isn't so simple.
1.
Is it really so big step ?
I must admit that in this moment I'm a little confuse with all this
tehnologies: JSP, Servlet.. .what to choose for my first web application.
2.
Could you please write me an example from real life with which technology is
developed: for example:
Servlet -> web app. for a table reservations in a restoran
Tom Dyess - 20 Mar 2005 05:19 GMT
> Until today I developed, small but usefull, desktop applications, using
> j2sdk. Now, I'm thinking about developing a web appllication.
[quoted text clipped - 9 lines]
> developed: for example:
> Servlet -> web app. for a table reservations in a restoran

No, I wouldn't say it isn't too big of a step, at least I can't think of a
good intermediary step. You will need to learn how web servers work from a
programming perspective, you will need to learn the j2ee api for
servlets/jsp/ejb and you will need to learn how to get it set up in a
server. I would start off by downloading tomcat and searching for jsp
tutorials. If you've ever done web with M$ technologies, JSP is similar to
ASP and Servlets are similar to ISAPI/NSAPI. I started off learning Servlets
because I've done a lot of ISAPI in the past. I don't particularly care for
ASP/scripting languages like that. I wrote an event driven tag parser for
the servlet that is capable of handling nested templates, so I don't have
any HTML in the servlet. Most people don't like Servlets as the web
application though, but I'm weird like that. Check out www.jsptut.com for
starters.

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Tom Dyess
OraclePower.com

HansF - 20 Mar 2005 14:48 GMT
> Until today I developed, small but usefull, desktop applications, using
> j2sdk. Now, I'm thinking about developing a web appllication.
[quoted text clipped - 4 lines]
>  I must admit that in this moment I'm a little confuse with all this
> tehnologies: JSP, Servlet.. .what to choose for my first web application.

Big?  Possibly.  Significant?  Absolutely, as you will be extending past
pure Java and need to be aware of other environments while developing.
Scary big?  No.

J2EE operates inside a J2EE container, which is a JVM with the required
J2EE libraries that runs 24x7. The container is made aware of your app by
placing the app components into a structured directory tree, by updating
the container's XML-based configuration, and (if necessary) by restarting
(virtual reboot) of the container.  Several apps could run in one
container, and an app can be spread across several containers.  SO you
will need to learn a new set of libraries.   Pick a container, such as
TomCat, to get started.

J2EE can be considered a superset of Java. You need to make sure your Java
is really solid, as you will be stepping into a world that references Java
through shortcuts and non-Java mechanisms such as tags. You will be
looking up things from external information sources and using the results
to affect code. Proficiency in XML as well as knowledge and understanding
of directory principals are an asset.

J2EE has 2 distinct sides - the Web side and the Business side. Perhaps a
contraversial statement, but I believe these take to distinct skill sets.
I point to the separate & independent certifications by Sun to support
this assertion. And I think it is rare to find excellence in both within
one person.

The Web side is largely represented by the JSP/Servlet world.  IMO, this
side shows the power of J2EE.  Reasonably easy to learn and very useful.
Points to a person with strong graphical serse as well as a strong Java
sense.  Especially when extending the JSP tag libraries, this requires a
good handle on how and when to split routines and expose functionality
segments.  Quite interesting and potentially very challenging.

The Business logic side can truly be a mind-twister at first. It comes
from a distributed object mind-set and requires a developer to think
concurrently in terms of local and remote controllers and local and remote
implementors.  I'd encourage waiting for this, or even looking for
alternatives to this side as I happen to agree with the authors of
"Better, Faster, Lighter Java".  

I refer you to the excellent http://www.theserverside.com site for
information and especially to the free downloadable reference books under
the articles section.

Also there is a misguided belief that one can write universally performant
database independent applications using J2EE. It is true that J2EE does
support database independence, but it does not (IMO, as yet 'can not')
take into account internal mechanisms such as locking, which can
dramatically affect programming methods. As a result I've found, except
for the most basic, even simplistic, applications, simply switching data
sources can give startling differences in performance.  

/Hans

The above is my opinion based on my experience.  I expect many challenges,
especially by people who have misread what I wrote.  Although I intend to
read responses, I will probably not respond to challenges. So let the
flames begin <g>!!


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