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Java EE has this "mysterious shroud" around it for younger Java developers - one that I've been trying to lift myself for quite a while with little success.
Confusion arises from:
Java EE seems to be both a library and a platform - there are multiple ways to "get" the Java EE library, typically from something like Oracle's Java EE SDK download. However, the Java EE library will not work, nor compile unless if your code is being run on or has access to a Java EE application server (such as JBoss, GlassFish, Tomcat, etc). Why? Can't the libraries function outside of the application server environment? Why do I need something massive as JBoss just to compile simple code to send an email?
Why are Java EE libraries not "standard" and included in the regular JVM download and/or the SDK?
Why are there so many Java EE offerings when there is really only two main flavors of standard Java (Oracle JVM/SDK | OpenJDK JVM/JDK)?
What can one do with Java EE that they cannot do with standard Java?
What can one do with standard Java that they cannot do with Java EE?
When does a developer decide they "need" Java EE?
When does a developer decide they do not need Java EE?
Why is Java EE library version not in sync with standard Java library releases (Java EE 6 vs. Java 7)?
Thanks for helping me clear the flog!
Why can't the libraries function outside of the application server environment?
Actually they can. Most of the libraries can be directly used standalone (in Java SE) or included in a .war (practically that's nearly always Tomcat). Some parts of Java EE, like JPA, have explicit sections in their respective specifications that tells how they should work and be used in Java SE.
If anything, it's not so much an application server environment per se that's at stake here, but the presence of all other libraries and the integration code that unites them.
Because of that, annotations will be scanned only once for all your classes instead of every library (EJB, JPA, etc) doing this scanning over and over itself. Also because of that, CDI annotations can be applied to EJB beans and JPA entity managers can be injected into them.
Why do I need something massive as JBoss just to compile simple code to send an email?
There are a few things wrong with this question:
For compiling you only need the API jar, which is below 1MB for the Web Profile, and a little over 1MB for the full profile.
For running you obviously need an implementation, but "massive" is overstating things. The OpenJDK for example is around 75MB and TomEE (a Web Profile implementation containing mail support) is only 25MB. Even GlassFish (a Full Profile implementation) is only 53MB.
Mail works perfectly fine from Java SE (and thus Tomcat) as well using the standalone mail.jar and activation.jar.
Why are Java EE libraries not "standard" and included in the regular JVM download and/or the SDK?
Java EE in a way was one of the first attempts to split up the already massive JDK into chunks that are easier to manage and download. People are already complaining that the graphical classes (AWT, Swing) and Applets are inside the JRE when all they do is run some commands on a headless server. And then you also want to include all the Java EE libraries in the standard JDK?
With the eventual release of modularity support we'll just have a small base JRE with many things separately installable as packages. Perhaps one day many or even all classes that now make up Java EE will be such package as well. Time will tell.
Why are there so many Java EE offerings when there is really only two main flavors of standard Java (Oracle JVM/SDK | OpenJDK JVM/JDK)?
There are more than just two flavors of Java SE. There is at least the IBM JDK, the previous BEA one (JRocket, which is being merged into the Oracle/Sun one because of the acquisition), various other open source implementations and a slew of implementations for embedded use.
The reason behind Java SE and EE being a specification is that many vendors and organizations can implement it and thus it encourages competition and mitigates the risk of vendor lock-in.
It's really no different with C and C++ compilers, where you have many competing offerings as well all adhering to the C++ standard.
Why is Java EE library version not in sync with standard Java library releases (Java EE 6 vs. Java 7)
Java EE builds on Java SE, so it trails behind. The versions do correspond though. Java EE 5 requires Java SE 5. Java EE 6 requires Java SE 6 and so on. It's just that mostly when Java SE X is current, Java EE X-1 is current.
Here are a few quickly composed answers to your questions...
Why can't JavaEE libraries function without an application server?
The services provided by JavaEE (container managed transactions, container managed dependency injection, timer service, etc..) inherently involve JavaEE compliant Application Servers (for example: GlassFish, JBoss, WebSphere, etc...). Therefore the JavaEE libraries serve no purpose without such a container. "Why do I need something as massive as JBoss just to compile simple code to send an email?" You don't. There are ways to send an email without JavaEE... But if you want to do it the JavaEE way, you need a JavaEE container.
Why are JavaEE libraries not included with JavaSE download?
The same reason that many libraries aren't included: it would be overkill. Since you can't even use the JavaEE libraries without an application server, why bother to include them? JavaEE should be downloaded if and when a developer installs an application server and decides to use JavaEE.
Why are there so many JavaEE offerings?
Are there really "so many" JavaEE offerings? If so, please list some of them. More accurately I believe there are multiple implementations of the same APIs.
What can one do with JavaEE that they can't do without standard Java?
Lots. You can't rely on an application server to manage transactions or persistence contexts without JavaEE. You can't allow an application server to manage EJB dependency injection without JavaEE. You can't use an application managed timer service without JavaEE. The answer to this question should make the answer to the first question quite clear... Most of the services provided by JavaEE require a JavaEE container.
What can you do with JavaSE that you can't do with JavaEE?
Um... I don't know.
When does a developer decide they need JavaEE?
This question is completely subjective... But if you need any of the services provided by JavaEE, you start to think about it. If you don't know what JavaEE is... you probably don't need it.
When does a developer decide they do not need JavaEE?
See previous answer.
Why is JavaEE library version not in sync with JavaSE version?
Good question. I won't pretend to know how to answer it... But I would guess the answer is: "because they're not in sync".
At bird's eye view, Java EE is a platform, i.e. something that we can build on.
Taking a more technical perspective, the Java Enterprise Edition standard defines a set of APIs commonly used for building enterprise applications. These APIs are implemented by application servers - and yes, different application servers are at liberty to use different implementations of the Java EE APIs.
However, the java ee library will not work, nor compile unless if your code is being run on or has access to a Java EE application server (such as JBoss, GlassFish, Tomcat, etc).
You compile against the Java EE APIs, so you only need those APIs at compile time. At runtime, you'll also need an implementation of these APIs, i.e. an application server.
Why do I need something massive as JBoss just to compile simple code to send an email?
You don't. However, if you wish to use the Java EE API for sending mail, you will need an implementation of that API at runtime. This can be provided by an application server, or by provided by a stand alone library you add to your classpath.
Why are Java EE libraries not "standard" and included in the regular JVM download and/or the SDK?
Because only the APIs are standardized, not the implementations.
Why are there so many Java EE offerings
Because people disagree on the right way to implement certain features. Because different vendors compete for market share.
What can one do with Java EE that they cannot do with standard Java?
Since Java EE implementations are built with "standard Java": Nothing. However, leveraging the existing libraries can save a great deal of effort if you are solving typical enterprise problems, and using a standardized API can prevent vendor lock-in.
What can one do with standard Java that they cannot do with Java EE?
Nothing, since Java EE includes Java SE.
When does a developer decide they "need" Java EE? When does a developer decide they do not need Java EE?
Generally speaking, the Java EE APIs solve typical, recurring problems in enterprise computing. If you have such problems, it usually makes sense to use the standard solutions - but if you have different problems, different solutions may be called for. For instance, if you need to talk to a relational database, you should consider using JPA. But if you don't need a relational database, JPA won't help you.
What is Java EE?
Let's start from canonicity definition at wiki:
Java Platform, Enterprise Edition or Java EE is Oracle's enterprise
Java computing platform. The platform provides an API and runtime
environment for developing and running enterprise software, including
network and web services, and other large-scale, multi-tiered,
scalable, reliable, and secure network applications.
The main point here is that Java EE is a platform provides an API, not some concrete library.
What for Java EE needed?
The main scope of Java EE is the network based applications, unlike Java SE oriented to the desktop applications development with simple network support. This is the main diference between them.
Scalability, messaging, transactioning, DB support for every application... the need in all of this has increased with the evolution of the network.
Of course a lot of ready solutions which Java SE provides are useful for network development, so Java EE extends Java SE.
Why do we need application servers to run our code?
Why do we need operation systems? Because there are a lot of painful work with hardware we need to do to make even simpliest application. And without OS you need to do it again and again. Oversimplified OS is just a programmatic container, which provides us a global context to run our applications.
And this is what the application servers are. They are allows us to run our applications in their context and provides us a lot of highlevel functionality which is needed for enterprise highloaded network applications. And we are don't want to write our own bicycles to solve this problems, we are want to write code which will satisfy our business needs.
Another example here could be JVM for Java.
Why Java EE doesn't contains onboard app server?
Hard to say for me. I think, it was done for more flexibility. Java EE says what they should do, they decide how to do it.
Why JVM doesn't include Java EE?
Because they directed to different market sectors. Java EE has a bunch of functionality which is doesn't need for usual desktops.
Why are there so many Java EE offerings?
Because Java EE only describes the behaviour. Everybody can implement it.
What can one do with Java EE that they cannot do with Java SE?
To conquer the internet. It's really hard to do with Java SE applets and sockets :)
What can one do with Java SE that they cannot do with Java EE?
As mentioned above Java EE extends Java SE, so with Java EE you should be able to do everything what is available for Java SE.
When does a developer decide they "need" Java EE?
When they need the power of Java EE. All what is mentioned above.
When does a developer decide they do not need Java EE?
When they write a usual console or desktop application.
Why versions of Java SE and Java EE are unsynced?
Java always had troubles with it's technologies naming and versioning. So this situation is not an exception.
Java EE is all about container concept. Container is an execution context within which will run your application and which provide this last a set of services. Each kind of service is defined by a specification named JSR. For example JSR 907, JTA (java transaction Api) which provide a standard way to manage distributed transaction against different resources. There are generally many different implementations for a given JSR, the implementation you will use depends on the container provider, but you don't really mind about that as you are sure the behavior respect the predefined contract : the JSR API. So to take advantage of Java EE, you need to run your application inside a container. The two main ones are EJB and servlet container which are both present on any Java EE certified application server.
The aim of all of this is to defined a standard execution environment to allow to package your application with only the essentials, id.est. your business. It avoids to depend on a unknown and various set of third-party libraries that you would have to package and provide with your app otherwise, and which may be sources of conflict with other apps on the server. In Java EE you know that all standard non functional requirements like security, transaction, scalability, remote invocation, and many more will be provided by the container (factorized for all apps running inside it) and you just have to base your work on its.
I have been doing Java SE for some years now and moving on to Java EE. However, I have some trouble understanding some aspects of Java EE.
Is Java EE just a specification? What I mean is: Is EJB Java EE?
Are EJB/Spring different implementations of Java EE?
I am sorry to ask but I have some difficulties to understand what Java EE is.
Could someone explain what Java EE is? And EJB?
(Updated Feb 2022)
First of all, "Java EE" has since Sep 2019 been renamed to "Jakarta EE", starting with version 8. Historically, there was also the term "J2EE" which covered versions 1.2 until 1.4. The term "Java EE" covered versions 5 until 8. See also Jakarta EE, History on Wikipedia.
Is Jakarta EE just a specification? What I mean is: Is EJB Jakarta EE?
Jakarta EE is indeed an abstract specification. Anybody is open to develop and provide a working implementation of the specification. The concrete implementations are the so-called application servers, like WildFly, TomEE, GlassFish, Liberty, WebLogic, etc. There are also servlet containers which implement only the JSP/Servlet part of the huge Jakarta EE API, such as Tomcat, Jetty, etc.
We, Jakarta EE developers, should write code utilizing the specification (i.e. import only jakarta.* classes in our code instead of implementation specific classes such as org.jboss.wildfly.*, com.sun.glassfish.*, etc) and then we'll be able to run our code on any implementation (thus, on any application server). If you're familiar with JDBC, it's basically the same concept as how JDBC drivers work. See also a.o. In simplest terms, what is a factory?
EJB is part of the Jakarta EE specification. Look, it's in the Jakarta EE API. Full-fledged Jakarta EE application servers support it out the box, but simple JSP/Servlet containers don't.
See also:
Where can I find a list of all the reference implementations for Java EE 6?
Java / Jakarta EE web development, where do I start and what skills do I need?
What to learn for making Java web applications in Java EE 6?
Are EJB/Spring different implementations of Jakarta EE?
No, as said, EJB is part of Jakarta EE. Spring is a standalone framework which substitutes and improves many parts of Jakarta EE. Spring doesn't necessarily require Jakarta EE to run. A bare-bones servlet container like Tomcat is already sufficient. Simply put, Spring is a competitor of Jakarta EE. E.g. "Spring" (standalone) competes EJB/JTA, Spring MVC competes JSF/JAX-RS/MVC, Spring DI/IoC/AOP competes CDI, Spring Security competes JAAS/JASPIC, etc.
Back during the old J2EE/EJB2 times, the EJB2 API was terrible to implement and maintain. Spring was then a much better alternative to EJB2. But since EJB3 (Java EE 5), the EJB API was much improved based on lessons learnt from Spring. Since CDI (Java EE 6), there's not really a reason to look at again another framework like Spring to make the developers more easy as to developing among others the service layer.
Only when you're using a bare-bones servlet container such as Tomcat and can't move on to a Jakarta EE server, then Spring is more attractive as it's easier to install Spring on Tomcat. It isn't possible to install e.g. an EJB container on Tomcat without modifying the server itself, you would basically be reinventing TomEE.
See also:
When is it necessary or convenient to use Spring or EJB3 or all of them together?
Java EE 6 vs. Spring 3 stack
Using JSF as view technology of Spring MVC
Java Enterprise Edition (Java EE) is an umbrella specification that references a number of other more detailed specifications, of which Enterprise JavaBeans (EJB) is one of the more important ones.
Read this - it explains the difference between Java EE and Spring
Thanks...
Source -- Java 2 Platform, Enterprise Edition (J2EE) defines the standard for developing component-based multitier enterprise applications. J2EE simplifies building enterprise applications that are portable, scalable, and that integrate easily with legacy applications and data .
Source -- Enterprise JavaBeans (EJB) technology is the server-side component architecture for Java Platform, Enterprise Edition (Java EE). EJB technology enables rapid and simplified development of distributed, transactional, secure and portable applications based on Java technology.
Is Java EE just a specification? What I mean is: Is EJB Java EE?
Java EE is a specification.
EJB is server side component architecture for Java EE
Are EJB/Spring different implementations of Java EE?
Both EJB and Spring are different frameworks following Java EE.
J2EE/JEE/Jakarta EE
Java Enterprise Edition (JEE) is used to develop distributed application &
web services.
It’s a component based approach to develop web app.
JEE web apps are considered as 3 tiered apps, since it is divided on 3
different machines/tiers
Client (Presentation)
J2EE sever (Application/Business)
Database (Data Access)
Everything you need to know about Java EE may be found by starting # Oracle official website, among other. You may also find interesting to read the specification APIs for release 8. It is worth taking the time to go through the Java EE 8 tutorial. You may want to start with it actually, because it provides a very good overview of the whole platform.
To put simply - JavaEE is a platform.
It is made up of many specifications which are just APIs. The specific concrete implementations of these APIs are the so called 'Reference Implementation'
EJB is just one specification within the JavaEE platform
No, Spring is a application framework that can allow you/has support for you to develop JavaEE applications
EJB is Enterprise Java Beans
Why is there so much confusion in the java world with various servers like apache, tomcat, jboss, jetty, etc and in .Net world it is just IIS that does that job. I would like to understand the need and use of it and am not starting a java vs. .net.
There are several reasons.
A Java EE app server is a transaction monitor for distributed components. It provides a number of abstractions (e.g., naming, pooling, component lifecycle, persistence, messaging, etc.) to help accomplish this.
Lots of these services are part of the Windows operating system. Java EE needs the abstraction because it's independent of operating system.
It should also be said that the full Java EE specification isn't necessary for developing web applications. JDBC, the part of Java that deals with relational databases, is part of Java SE proper. Java EE adds on servlets, which are HTTP listeners, and Java Server Pages, which is a markup language for generating servlets. You can develop fully functional web applications using just these technologies and Java SE. Tomcat and Jetty are two servlet/JSP engines that can stand in for full Java EE app servers.
If you take note of the fact that .NET has HTTP listeners built into the System.Net module, you realize that it's as if .NET took a page from Java and folded the javax.servlet functionality into the framework.
If you add Spring and a messaging functionality like ActiveMQ or RabbitMQ, you can write complete applications without having to resort to WebLogic, WebSphere, JBoss, or Glassfish. You don't need EJBs or the full Java EE spec.
UPDATE:
Spring Boot offers the possibility of developing and running full-featured Java applications as an executable JAR file. There's no need for any Java EE app server, just JDK 8 or higher.
This is because Sun and Microsoft had very different goals with their software, and ways to reach that goal.
The Sun mantra for Java has been right from the beginning "Write once, run everywhere", and that has resulted in that much effort has been put into creating _API_s that specify how the environment should look like to allow a minimalistic piece of code do its job.
The API for "process a web request and return a web response" was named Servlets, and has been extremely successful due to it filling a void and being well specified. All mainstream Java based web servers I know of allow to run servlets. An early implementation of a complete servlet capable web server is only 1500 lines Later this was expanded to include JSP's to provide for HTML with server side code (like PHP).
For any solution to be truly scalable, including web solutions, it means that eventually the load is so high that one computer is not powerful enough to run it on its own anymore. A scalable solution MUST be able to spread over multiple computers aware of each other, and that single requirement brings a LOT of other things to the table:
Code must be able to invoke code running on a different computer (EJB's).
Data must be available to all computers in a consistent way (database).
Access to said database must be efficient (database connection pooling).
... and much much more
Sun then created API's for all of the functions they found were necessary for this to run, and named it "Java Enterprise Edition" (those days the word "Enterprise" was used for a lot of things), and created a system implementing all these API's which people could buy and use.
The difference between Microsoft and Sun now comes in play. Here Microsoft would just make IIS public, and say "use these API's" in clients but not actually want anybody to create another server providing these APIs. Because they want to sell Windows to run it!
Sun wanted people to use the language instead, so they made it possible for ANYONE to implement the Java EE specification, but they had to pass a rigorious test suite from Sun (and pay) to be allowed to use the Java EE brand. This has caused a large number of Java EE servers to be available where you usually can reuse the core business logic, but have to configure the Java EE server to provide the resources the application needs.
See http://en.wikipedia.org/wiki/Java_Platform,_Enterprise_Edition#Certified_application_servers for the state of servers today. Both commercial and open source are available based on your needs - pick the one that suits you best.
So, the reason is that Java EE is a set of well defined API's that anyone can implement, and they have.
First off, you can run .NET code off Apache using mod_mono, so it is not limited to IIS. There are also several other web servers (Cassini and XPS come to mind) that will run ASP.NET as well.
In order to run a dynamic web application you need both a web server and an application server. Sometimes these integrate so well they appear to be one and the same, sometimes not.
In regards to Java - it has always supported more platforms than .NET and has been more open, therefore got integrated to more web servers (on the Linux stack).
As both .NET and IIS are technologies that came from Microsoft, ASP.NET and the application server aspects of it (aspnet_isapi.dll) were bundled with IIS and the different .NET installers integrate with IIS. Of course, Microsoft only implemented it on their OS and for their web server.
Apache is very analogous to IIS, and doesn't have much to do with Java.
Application Servers in Java provide additional services that .NET provides in various ways, with different products or from the Windows operating system.
Apache is typically used in Java deployments as a proxy to an application server behind it, and potentially serves static content, or handles SSL, and similar concerns. It is entirely optional, although there are good reasons to use it.
Tomcat and Jetty are basically java web servers, which provide a defined framework (Servlets among other things) for creating dynamic web sites with Java code. They are often components of a larger application server, or can be deployed alone.
JBoss is an example of an application server (Glassfish and Weblogic are two very common others), which provides the full J2EE specification. The idea behind the J2EE specification is to allow a defined way to build an application server so that an application can be switched between different application servers from different vendors that comply with the spec. The specification is about how to interact with defined services that are useful for server-side program.
Because Java EE is a specification, not a product itself. Remember that Java is a lot more open than .NET (In the specification sense).
Each application server has different features, different performance, different target users/enterprises, different price tags, runs in different platforms, require different hardware. Differentiation is why those all application servers exists, one size does not fit all.
One reason is that writing a servlet is as easy as implementing the javax.servlet.Servlet interface in a concrete class. Servlet containers, then, only need to support a fairly simple API in order to call themselves web servers. This makes setting out to develop a servlet container extremely simple because of this limited contract of functionality.
The choices off tools are one of the advantages and disadvantages of Java, look at the available Java Web Developement Frameworks,you could evaluate them endlessly just to decide. in .Net it's pretty much MVC. With servers it's relatively simple. Most go to Tomcat if they need a web server and JBoss if they need a free application server though. The reasons for this have already been said, J2EE is a specification.
in a tutorial they asked me to install the application server which could be downloaded from their site.
what do they mean with application server?
the link they provided: http://java.sun.com/javaee/downloads/index.jsp
i mean come on sun, all these names. jdk then j2ee..and when i wanna download j2se it says jdk6. r they insane? a lot of people are wondering what is what...they just dont know how to name things.
however, back to the question. so with application they mean java ee server?
i've got a mac and people say java is already installed. what is installed exactly? the j2ee or j2se? do i have do download j2ee? Java is just killing me...
EDIT: read something about that the application server is a name for ee server. and there are many ee servers like tomcat, jetty and glassfish. and i know these sometimes are called servlet containers.
so that makes application server = ee server = servlet container?
and jdk = j2se? so j2ee != jdk?
Sun's Application Server has been superseded by the community app server, GlassFish.
The JavaEE download page only has two JavaEE6 download links and both contain versions GlassFish v3. Chances are you only need the web profile, but download the full version if you aren't sure.
Note that GlassFish is just the reference Application Server. You also have other Application servers, such as Apache Geronimo and Oracle Weblogic... as well as ones that are just servlet containers, like Apache Tomcat and Jetty. These types should correspond to GlassFish's normal and web profiles respectively.
These other servers only require a JRE to run applications, or the JDK to develop for them.
Side Note: GlassFish v3 is the only JavaEE 6-compliant server... JavaEE 6 is brand new. The others should be JavaEE 5 compliant.
Also, JavaEE is the new name for J2EE, as sun tries to move away from the Java 2 name.
What do they mean with application server? The link they provided: http://java.sun.com/javaee/downloads/index.jsp
An application server is a component-based middleware used in server centric N-tier architecture. It manages the life-cycle of components deployed on it, it provides services for state maintenance, data access (with pooling of resources), security, clustering and fail-over.
AFAIK, one of the first application server (as just defined above) was ATG Dynamo. Other proprietary application servers include BroadVision, ColdFusion, etc. But none of them really survived to the advent of Java application servers (understand application servers based on the standards defined by Java EE and the Java language).
I mean come on sun, all these names. (...)
Wikipedia does a pretty good job at defining what Java SE is:
Java Platform, Standard Edition or Java SE is a widely used platform for programming in the Java language. It is the Java Platform used to deploy portable applications for general use. In practical terms, Java SE consists of a virtual machine, which must be used to run Java programs, together with a set of libraries (or "packages") needed to allow the use of file systems, networks, graphical interfaces, and so on, from within those programs.
The JRE (Java Runtime Environment) provides the virtual machine and the set of libraries i.e. everything you need to run Java software. The JDK (Java Development Kit) provides a JRE plus a compiler (javac) and some other tools i.e. everything you need to run and develop Java software.
Java EE is a specification (more precisely, a set of specifications) built on top of the libraries provided by Java SE and is more server-side oriented. Implementations of this specification are provided by Java application servers: GlassFish is Sun's implementation, JBoss is RedHat's implementation, WebLogic is BEA Oracle's implementation, WebSphere is IBM's implementation, etc.
Regarding the versions and nomenclature, yes, Sun is crazy. It was an horrible mistake to introduce this "Java 2 Platform, Standard Edition" naming when the version 1.2 came out. I can imagine how confusing this is. But, again, Wikipedia does a great job at clarifying this in the section Nomenclature, standards and specifications:
Java SE was known as Java 2 Platform, Standard Edition or J2SE from version 1.2 until version 1.5. The "SE" is used to distinguish the base platform from Java EE and Java ME. The "2" was originally intended to emphasize the major changes introduced in version 1.2, but was removed in version 1.6. The naming convention has been changed several times over the Java version history. (...)
This should make things more clear.
(...) however, back to the question. so with application server they mean java ee server?
Yes, this is what they mean or, more precisely, they mean Sun GlassFish Enterprise Server (previously named Sun Java System Application Server). Source: http://developers.sun.com/appserver/.
I've got a mac and people say java is already installed. what is installed exactly? the j2ee or j2se? do i have do download j2ee? Java is just killing me...
A JRE or a JDK (if javac available, it's a JDK), so only the Java SE part. And actually, if you are still following me, you don't download Java EE, you download something providing an implementation of it (i.e. an application server).
(...) so that makes application server = ee server = servlet container?
No. To simplify, a Java EE server = Servlet container + EJB Container. Some server are only Servlet container (like Tomcat, Jetty), they don't provide the EJB container part and thus don't fully implement the Java EE specification and can't be considered as full Java EE servers.
and jdk = j2se? so j2ee != jdk?
I hope I covered this with my answer.
In order to run you Java EE applications you need an application server.
The link you provided is to download GlassFish that is one application server.
There are others application servers like Apache Tomcat, Jboss.
JDK stands for Java Development Kit
You need this to develop Java applications.
JRE stands for Java Runtime Environment
You need this to run Java applications.
GlassFish with the Java EE SDK (provided on the link you gave) is what you need. Java EE server = application server.
What is installed on your Mac by default is probably only a JRE (runtime environment) and not a JDK (development kit). Which means, you can run Java apps but not develop. By downloading GlassFish with the Java EE SDK, you'll get the full-blown SDK you need and a server to deploy on.
Hope that helps.
This question already has answers here:
Difference between Java SE/EE/ME?
(14 answers)
Closed 7 years ago.
What's the main difference between Java SE and Java EE?
Java SE (formerly J2SE) is the basic Java environment. In Java SE, you make all the "standards" programs with Java, using the API described here. You only need a JVM to use Java SE.
Java EE (formerly J2EE) is the enterprise edition of Java. With it, you make websites, Java Beans, and more powerful server applications. Besides the JVM, you need an application server Java EE-compatible, like Glassfish, JBoss, and others.
Java SE stands for Java standard edition and is normally for developing desktop applications, forms the core/base API.
Java EE stands for Java enterprise edition for applications which run on servers, for example web sites.
Java ME stands for Java micro edition for applications which run on resource constrained devices (small scale devices) like cell phones, for example games.
http://www.dreamincode.net/forums/topic/99678-j2se-vs-j2ee-what-are-main-differences/
As far as the language goes it is not as though java changes. Java EE has access to all of the SE libraries. However EE adds a set of libraries for dealing with enterprise applications.
Java EE is more like a "platform" or an general area of development.
In Java SE you write applications that run as standalone java programs or as Applets. In JavaEE you can still do this, but you can also write applications that run inside of a Java EE container. The container can do a great amount of management for you such as scaling an application across threads, providing resource pools, and management features.
Java EE has a web framework based upon Servlets. It has JSP (Java Server Pages) which is a templating language that compiles from JSP to a Java servlet where it can be run by the container.
So Java EE is more or less Java SE + Enterprise platform technologies.
Java EE is far more than just a couple of extra libraries (that is what I thought when I first looked at it) since there are a ton of frameworks and technologies built upon the Java EE specifications.
But it all boils down to just plain old java.
Java SE refers to the standard version of Java and its libraries. Java EE refers to the Enterprise edition of Java which is used to deploy web applications.
Java EE is enterprise edition.
Includes jsp, servlets, beans, and some other stuff for server programming.
Java SE is standard edition. This is plain old Java. Includes GUI stuff.
First, J2SE and J2EE have been renamed. They're now Java SE and Java EE.
Essentially, Java SE is your standard Java designed for end-users. That's what you'd develop to for desktop applications. Java EE is the enterprise edition, designed for server programming, such as SOA and web applications.
Best description i've encounter so far is available on Oracle website.
Java SE's API provides the core functionality of the Java programming language. It defines everything from the basic types and objects of the Java programming language to high-level classes that are used for networking, security, database access, graphical user interface (GUI) development, and XML parsing.
The Java EE platform is built on top of the Java SE platform. The Java EE platform provides an API and runtime environment for developing and running large-scale, multi-tiered, scalable, reliable, and secure network applications.
If you consider developing application using for example Spring Framework you will use both API's and would have to learn key concept of JavaServer Pages and related technologies like for ex.: JSP, JPA, JDBC, Dependency Injection etc.
Java SE contains all the base packages. Some of the base packages are written in Java and some are written in C/C++. The base packages are the fastest because there are no additional layers on top of their core functionality.
Java EE is a set of specifications and the respective implementations are all built using Java SE base packages which happen to already contain everything required for any application. For example, for a web application, here is a Java SE Web Server and a Java SE Database.
Java SE 9/10 is expected to contain better support for native in order to improve the inherent performance issues it has from being an interpreted language. Using the enormous Java EE implementations implies a willingness to sacrifice performance, scalability and a lot of time and money for education and updates, in exchange for project standardization.
JavaSE and JavaEE both are computing platform which allows the developed software to run.
There are three main computing platform released by Sun Microsystems, which was eventually taken over by the Oracle Corporation. The computing platforms are all based on the Java programming language. These computing platforms are:
Java SE, i.e. Java Standard Edition. It is normally used for
developing desktop applications. It forms the core/base API.
Java EE, i.e. Java Enterprise Edition. This was originally known as
Java 2 Platform, Enterprise Edition or J2EE. The name was eventually
changed to Java Platform, Enterprise Edition or Java EE in version 5.
Java EE is mainly used for applications which run on servers, such as
web sites.
Java ME, i.e. Java Micro Edition. It is mainly used for applications
which run on resource constrained devices (small scale devices) like
cell phones, most commonly games.
In Java SE you need software to run the program like if you have developed a desktop application and if you want to share the application with other machines all the machines have to install the software for running the application. But in Java EE there is no software needed to install in all the machines. Java EE has the forward capabilities. This is only one simple example. There are lots of differences.
The biggest difference are the enterprise services (hence the ee) such as an application server supporting EJBs etc.