Re: JSP vs ASP

[Gary L Peskin <garyp@xxxxxxxxxxxx>]

Joe --

Not sure if I know the official differences but here is my
understanding:

JSP -- This is basically a set of HTML-like tags that you can embed in
an HTML page.  When interpreted by a JSP capable server (like
WebSphere), these tags cause pre-existing java programs to be invoked
and the return values from the programs are embedded in the resulting
HTML page.  JSP has lots of other capabilities, including embedding
actual java program statements (called scriptlets) which are also
interpreted by the JSP engine.  This basically allows a non-programmer
to invoke pre-existing programs directly from an HTML page.  This could
be used, for example, to allow a page to display a list of items in a
shopping cart by repeatedly invoking a java program that returns a new
item on each call.

Servlets -- These are java programs that run on the server.  Applets are
java progams that run on the client (ie browser).  Servlets follow
special programming rules and extend javax.servlet and
javax.servlet.http which are included in the JSDK (Java Servlet
Development Kit).  Servlets are invoked by a servlet engine (like
WebSphere) or are directly supported by some web servers.  They're sort
of like CGI programs except they use a different standard and don't
require the creation of a separate process like CGI programs so they
have much lower overhead.

You can find out all about these two items on the 400 (and more) by
visiting 

http://www.as400.ibm.com/tstudio/websphere/docs/as400v202/index.html

or 

http://www.as400.ibm.com/tstudio/websphere/docs/doc.htm

Enterprise Java Beans -- First thing to know is that EJBs have almost
nothing to do with JavaBeans, except the name.  EJBs are distributed
java programs which are accessed remotely.  In other words, a java
program running on a client can follow EJB conventions and locate an EJB
on a server somewhere, even if the client doesn't know on which server
the target EJB resides.  Then, it can cause the server to make new
copies of the component and it can invoke methods on the component on
the remote machine.  Programs written to follow the EJB standard
interact with an EJB server which provides mangement services (like
COMMIT/ROLLBACK, statistics gathering, resource management,
writing/reading from a database, etc) so that the individual programs
are freed from a lot of the bookkeeping chores.

If you've ever used CICS on the mainframe, you know that CICS programs
are written using the CICS API and that CICS performs the actual
services.  EJBs are sort of similar to an object-oriented version of a
CICS program running on a distributed system.  EJB servers, called
Component Transaction Monitors, are like souped up object-oriented
versions of CICS itself.  I've just finished reading an excellent book
on EJBs called "Enterprise JavaBeans" by Richard Monson-Haefel published
by O'Reilly.  ISBN is 1-56592-605-6.  I highly recommend it.

HTH,
Gary

Joe Teff wrote:
> I'm in the early stages of learning Java and one thing that I notice is that
> terminology is constantly growing. Can some explain (simple explanation
> is fine) what JSP, servlets and Enterprise Java Beans are? TIA
> 
> Joe Teff
+---
| This is the JAVA/400 Mailing List!
| To submit a new message, send your mail to JAVA400-L@midrange.com.
| To subscribe to this list send email to JAVA400-L-SUB@midrange.com.
| To unsubscribe from this list send email to JAVA400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner: joe@zappie.net
+---