Databases Reference
In-Depth Information
C H A P T E R 1
OHS, EPG, and
APEX Listener Compared
By John Edward Scott
When I first started using APEX, I didn't really have a choice when it came to deciding which web server
to use; in a similar vein to the often-quoted Henry Ford (“any colour as long as it's black”), it was a case
of “Use any web server as long as it's the OHS”. The
OHS
is the commonly used name for the Oracle
HTTP Server.
However, as with all things technology related, times change. Oracle 9i Release 2 brought XML DB
and with it an embedded web server. As of Oracle 10g Release 2, this embedded web server can be used
as an embedded PL/SQL gateway to run PL/SQL via a browser. It is commonly known as the
EPG
(Embedded PL/SQL Gateway) and controlled via the DBMS_EPG package.
So, things were good: we now had a choice of the OHS and the EPG, both of which were officially
supported by Oracle. But, never being content to sit on their laurels, the Oracle team decided to give us a
third option, the APEX Listener, which is a J2EE alternative to the OHS. The APEX Listener was created to
explicitly fulfill the needs of the web server that has to sit between the web browser and your Oracle
APEX application, but it can also support many other configurations, since it can be deployed using
Oracle Web Logic Server (WLS), Oracle Glassfish Server, and OC4J.
Why Should I Care About This Chapter?
When I first came up with the idea for this topic (and before I'd approached the other authors), I thought
a lot about what sort of chapter I'd write. There are so many areas of APEX that interest me, particularly
with the release of APEX 4.0, it seemed like an impossible choice. I learned with my first topic,
Pro Oracle
Application Express,
that no matter what you write about, some people will love a chapter while others
won't find it that relevant to them.
So, I thought to myself, what is the one thing that everyone who uses APEX has to use, yet probably
never gives a second thought to? The answer (of course!) is the web server aspect.
You might be thinking “Okay, but I'm going to skip this chapter, because that's something my
System Admin takes care of.” Well, dear reader, please bear with me. As an APEX developer myself, I
know that there are things you can do with your web-server configuration that will really impact the
performance and scalability of your APEX applications (you should care about that!), and there are also
some really great features available in the web server than you can leverage in your applications (and
you should care about that!).
So, while at first glance this chapter might not seem as cool, sexy, or “APEX 4.0” as some of the other
chapters in this topic, I hope that you will find some things that make you think or, even better, make
you use them!
