Java EE is a Java platform (Java EE Components in picture) [ JavaEE Platform, Technologies, all APIs ] designed for the mainframe-scale computing typical of large enterprises, see Enterprise App. Mode. java ee
Sun Microsystems (together with industry partners such as IBM) designed J2EE to simplify application development in a thin client tiered environment. J2EE simplifies application development and decreases the need for programming and programmer training by creating standardized, reusable modular components and by enabling the tier to handle many aspects of programming automatically. [1]

Java EE Platform includes Java Standard Edition plus most of the other Java technologies including Java Specialized Topics, Activation, JMS (Java Messaging Service), EJB and more others . Most of the APIs are very component-oriented and are intended to provide pluggable interfaces for business components to form robust, distributed internet applications.     See more about: Java EE Components, Java EE Tutorials and Application Servers.

About Java Servlets, JSPs, JSFs, Portlets and EJBs

A servlet (for creating Java web-apps, 2) is a Java programming language class used to extend the capabilities of servers that host applications accessed via a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by Web servers. For such applications, Java Servlet technology defines HTTP-specific servlet classes. JSP is a technology, not a language. It allows Web page authors to put dynamic data into a Web document with Java statements embedded in special HTML tags. The embedded Java statements will be executed by the JSP enabled Web server, not by the Web browser. On the Web, a portlet (see more: Open Source Portals in Java) is a component of a portal Web site that provides access to some specific information source or application, such as news updates, technical support, or an e-mail program among many other possibilities. Portals aggregate different content into a single interface; portlets connect the user to specific content within that interface. Most portals offer a selection of portlets that the user can select for a customized interface. Portals connect to portlets through portlet APIs (application programming interfaces). JSF is a component based MVC framework which is built on top of the Servlet API and provides components in flavor of taglibs which can be used in JSP or any other Java based view technology such as Facelets. An EJB (tutorial, see also Spring and EJB Framework), Enterprise JavaBeans, is a managed, server-side component architecture for modular construction of enterprise applications.
Java web services (Building Web Services with JAX-WS) provide a standard means of interoperating between software applications running on a variety of platforms and frameworks. Whereas RESTful web services (examples: JAX-RS, Spring REST) are built to work best on the web on an architectural style REST.
Books more about the Java EE components: JSP and JSTL Tutorials, Java for the WEB, Web Development, Head first servlets & JSP, Portlets for Portals, What is portlet, Liferay Portlet Framework, Ejb 3 in Action, Liferay Portlet Framework, Pro EJB 3: Java Persistence API, Pro JPA 2, JSTL in Action, Java Server Faces In Action, Enterprise Practices, Pro JSF and Ajax: , Portlets in Action, Liferay in Action

Java EE Tutorials

Other Tools: Java Toolkit • API's • Programmer's Corner • WebDev. Tools • Database Tools • Modeling & Design • Multimedia • Maths and Science

Application Servers ⇧

An application server is a server program that handles all application operations between users and an organization's backend business applications or databases. Application servers are typically used for complex transaction-based applications. To support high-end needs, an application server has to have built-in redundancy, monitors for high-availability, high-performance distributed application services and support for complex database access. See the following application servers and other Web Servers in Java, Network Servers in Java:

  • Apache Geronimo - is the flexible Java App. server, designed by component based architecture and enables to customize server functions. About, Tutorial, Users
  • WildFly (JBoss) - is a J2EE platform for developing and deploying enterprise Java apps, Web apps and services, and portals. Home, JBoss, JBossIDE, JBoss Seam, 2
  • Glassfish - Glassfish Application Server is fully JEE 7 complaint application app. server. It is open source, which can be used to develop and deploy java based enterprise applications. About, QuickStart, integration, Tutorial, 2
  • WebSphere - enables programmers to develop, deploy and integrate the secure, scalable, and flexible e-business apps. About, API, Base, Migration
  • Weblogic - is a server software application that runs on a middle tier, between back-end databases and related apps and browser-based thin clients. Home, About

Comparision of application servers: J2EE Performance, Resin, Apache ISS, Tomcat alternatives, App.Servers, Comparison, 2, 3, is Tomcat ..?

Suggested Reading: J2EE Containers • Web Container • WebLogic • Load Balancing • L.B. Architectures • L.B and failover • Clustering and L.B
• JBoss clustering • CORBA Technology • with Java • 2 • CORBA Technology • JOnAS • JBoss at Work • CORBA and Applets/SecurityManager

References

  1. 1. Java EE at a Glance
  2. Java Platform, Enterprise Edition
  3. Make the Future Java
  4. Java EE 7 Launch Webinar Technical Breakouts
  5. Java EE 7 Technologies