Hi,I have a few confusions about J2SE and J2EE. If you can help toclarify, that would be great.1. What is the biggest difference between J2SE  and J2EE? Is it justthat J2EE contains a few more extras libraries?2. When I installed Java EE 5, the JRE installed is Java SE Run Timelibrary 6. Does it mean that J2EE and J2SE uses the same JRE?3. Another question is regarding the J2EE implementations, like JBossand Sun Java System Application Server. Where does this piece comeinto play? What is it used for? If I wrote an application with J2EE,do I only need the JRE to run it, or I need the application servers torun it?Thanks.

zhangyuewuliu@gmail.com wrote:> Hi,> > I have a few confusions about J2SE and J2EE. If you can help to> clarify, that would be great.> > 1. What is the biggest difference between J2SE  and J2EE? Is it just> that J2EE contains a few more extras libraries?JSE (they dropped the "2") is the core Java language and APIs.  JEE (they dropped the "2") is a collection of specifications for web-enabled development.The phrase "just that X contains a few more extras [sic] libraries" makes it sound like libraries aren't important.  They are.  It isn't "just" that JEE specifies more libraries, it's what those libraries can do.> 2. When I installed Java EE 5, the JRE installed is Java SE Run Time> library 6. Does it mean that J2EE and J2SE uses the same JRE?The JRE is an implementation of JSE.  Let me say that again: the JRE /is/ your JSE.  JSE doesn't "use" the JRE - the JRE is your JSE.  Similarly, Tomcat or JBoss or Sun App Server or WebSphere or Oracle App Server or BEA ... is your JEE.> 3. Another question is regarding the J2EE implementations, like JBoss> and Sun Java System Application Server. Where does this piece come> into play? What is it used for? If I wrote an application with J2EE,> do I only need the JRE to run it, or I need the application servers to> run it?JBoss or Tomcat or whatever is your JEE.  Without one (or more) of those you don't have JEE.  You need an application server to run such an application.Put another way, to run JEE you must have JEE.There are tutorials on java.sun.com.  Also, GIYF and WIYF.-- Lew

Thanks for the reply. I still have one question that confuses me.1. I know JBoss and the Sun App Server is an implementation for JEE.but is Tomcat a complete implementation for JEE, or it only supportsthe servlet and JSP part of the JEE specification?2. So for JSE, sun provides the implementation as JRE. But for JEE, alot of vendors are providing different implementations. Is there areason for that?Thanks.

zhangyuewuliu@gmail.com wrote:> 1. What is the biggest difference between J2SE  and J2EE? Is it just> that J2EE contains a few more extras libraries?J2SE/JSE = compiler and other tools + virtual machine + basic libraryJ2EE/JEE = enterprise library + some specifications that provide a            contract between the compliant applications and the            compliant app servers> 2. When I installed Java EE 5, the JRE installed is Java SE Run Time> library 6. Does it mean that J2EE and J2SE uses the same JRE?J2EE/JEE needs a J2SE/JSE implementation.> 3. Another question is regarding the J2EE implementations, like JBoss> and Sun Java System Application Server. Where does this piece come> into play? What is it used for? If I wrote an application with J2EE,> do I only need the JRE to run it, or I need the application servers to> run it?Your J2EE/JEE application needs an J2EE/JEE application serverand both need a J2SE/JSE implementation.Arne

Lew wrote:> zhangyuewuliu@gmail.com wrote:>> 1. What is the biggest difference between J2SE  and J2EE? Is it just>> that J2EE contains a few more extras libraries?> > JSE (they dropped the "2") is the core Java language and APIs.  JEE > (they dropped the "2") is a collection of specifications for web-enabled > development.Actually JEE can be used in non web context. It is not so common,but it is seen.Arne

zhangyuewuliu@gmail.com wrote:> 1. I know JBoss and the Sun App Server is an implementation for JEE.> but is Tomcat a complete implementation for JEE, or it only supports> the servlet and JSP part of the JEE specification?No - Tomcat is not a complete JEE implementation.> 2. So for JSE, sun provides the implementation as JRE. But for JEE, a> lot of vendors are providing different implementations. Is there a> reason for that?Same thing.SUN, IBM, BEA, Oracle and possible other does all provide a JSEimplementation (both in JDK and JRE flavour - JDK has compilerand some other development tools - JRE does not).Redhat/JBoss, IBM, BEA, SUN, Apache (Geronimo not Tomcat !),ObjectWeb, Pramati etc. all provide JEE application servers.Arne