J2SE,J2EE,JRE confused?

[Mike Jones]

As a developer, when (if ever) do I need to install J2EE rather than J2SE? For example, I am running jdk1.3.1 standard edition only on my client PC, and can still test JSP via Forte and Tomcat. Does that mean Web and EJB servers provide the J2EE specification support, and I only need to install the base J2SE jdk in my development environment? And one more lame question. I am running an application server on a server (second PC) with just the runtime (JRE) installed. I don't need to compile on the server, just deploy to, so that should be fine. But, is there a difference between J2SE JRE and J2EE JRE. I have searched the Sun site and can't determine the answer.
Confused,
Mike

[JeanLouis Marechaux]

J2EE has to be installed if you need enterprise features, like EJB , Servlets....
J2xRE is the Runtime environment, to be able to "run" java programs without having the full J2xE installed
[This message has been edited by Bill Bailey (edited December 19, 2001).]
[This message has been edited by Bill Bailey (edited December 19, 2001).]

[Mike Jones]

Bill,
I know JRE is the runtime, and I know J2EE is the overall spec which includes EJB, JSP, yada yada yada.
I just don't get when or if ever I need to install J2EE as a developer. You would think I would not be able to test JSP pages on my client machine, since I have only installed J2SE jdk1.3.1. However, I can using Forte which includes Tomcat. This leads me to believe application\web servers (i.e. Tomcat) and tools will provide me with J2EE additions to the J2SE, and as a developer, I will not need to install J2EE, just J2SE. What am I missing?
Also, is there a J2SE JRE and a J2EE JRE, or only one? Definitely rookie questions, but I find the Sun site very confusing.
Mike

[Mike Jones]

OK, after spending some more time on the Sun website, I will try and answer my own question. I would appreciate anyone pointing out where I am off base.
J2EE is based on J2SE. A developer can install the J2EE SDK which includes the RI (Reference Implementation), and use that to develop J2EE applications with.... OR you can use commercial products which implement the J2EE specification (which would make the premise that you don't need to install the J2EE SDK correct). This also would explain why there is only one JRE. It takes the JRE plus the Sun J2EE SDK RI, or JRE plus commercial J2EE products for the J2EE dance.
Have I got it, or am I smoking something?
Also, assuming the above is correct. If I do go ahead and install the J2EE SDK, do I need to install anything else (i.e. JRE? and / or J2SE SDK). On linux, an install of the J2SE SDK does not automatically include the JRE.
Mike

[JeanLouis Marechaux]

My apologies for my misunderstanding of your first question.
And I can't answer the second as I don't know Forte
But there is no JRE "enterprise" as the enterprise code is run in a server container and of course, the container is able to run Java without any JRE.
In your case, having Tomcat installed on each machine is just like having a servlet container on each machine...That's why you can run servlet and JSP
HTH

[Tim Holloway]

Forte contains Tomcat and Tomcat requires J2EE, so Forte contains that as well. Essentially when you install Forte, you get the kitchen sink. And it shows. Although I can run a Tomcat server on a P-233 with about 160MB RAM, Forte sends a 384MB P400 near the melting point.
There's no overlap between the JDK/JRE (aka J2SE) and J2EE libraries. If you want the extra features of J2EE (servlet and EJB compilation for example), you have to have J2EE installed. J2SE is a prerequisite for all standard Java development. "Standard" meaning you're not running a special platform like J2ME.

[Mike Jones]

Bill and Tim,
Thanks. This is the stuff they should nail down in the SCPJ2 exam, rather than File IO.
Not to beat a dead, horse, but one more question, Tim. You said if I want the extra features of J2EE (servlets,EJB,...), I have to install J2EE. Obviously I get the servlet portion of J2EE with Forte without any extra install. I proved that by running a JSP page and compiling into a servlet with Forte. What about EJBs. I haven't got there yet with Forte. Do I have to install something extra (EJB container) to COMPILE EJB, or just something extra to RUN EJB?
Thanks in advance,
Mike

[JeanLouis Marechaux]

Mike,
there is 2 different thinks.
First, to be able to compile EJB classes, you need the J2EE package in your classpath.
It meens you have to download it or to use an IDE EJB compliant (Jbuilder, PowerJ, VAJ... ).
Forte for java 3.0 is EJB compliant
Then if you want to "run" EJBs, you need an EJB container.
Then take a look at products like BEA WebLogic, IBM WebSphere, Sybase EAServer, jBoss ...

[Mike Jones]

Originally posted by Bill Bailey:
Mike,
there is 2 different thinks.
First, to be able to compile EJB classes, you need the J2EE package in your classpath.
It meens you have to download it or to use an IDE EJB compliant (Jbuilder, PowerJ, VAJ... ).
Forte for java 3.0 is EJB compliant
Then if you want to "run" EJBs, you need an EJB container.
Then take a look at products like BEA WebLogic, IBM WebSphere, Sybase EAServer, jBoss ...

Hey Bill. Two different Thinks. I like that. Discussing J2EE via a bulletin board is a challenge. I don't think I asked my question very clearly, but your answer is pretty much what I came up with also. I'm familiar with the J2EE spec (I have ORION and JRUN installed on a linux server). My questions are strictly related to setting up a development environment on my client box. I just need to try and compile an EJB with Forte CE. Forte CE provides for JSP, but alot of the Forte EJB features require the Enterprise version. My guess is, you are good to go for compiling EJB with Forte CE, but not for running. I suspect running EJBs on my client box will require installing either the Sun RI J2EE or some other EJB container on my client PC.
It never changes. Half the battle of learning any language or platform is learning how to setup the development environment. I find the Java world and the Sun website in particular very confusing. That's fine. That's why we will be worth the big $$$.
Thanks,
Mike
[This message has been edited by Mike Jones (edited December 21, 2001).]
[This message has been edited by Mike Jones (edited December 21, 2001).]