Monday, January 18, 2010

Definitions of JRE JDK JVM J2SE J2EE

Java SE Overview

There are two principal products in the Java SE platform family: Java SE Runtime Environment (JRE) and Java Development Kit (JDK).



Java Runtime Environment (JRE)
The Java Runtime Environment (JRE) provides the libraries, the Java Virtual Machine, and other components to run applets and applications written in the Java programming language. In addition, two key deployment technologies are part of the JRE: Java Plug-in, which enables applets to run in popular browsers; and Java Web Start, which deploys standalone applications over a network. It is also the foundation for the technologies in the Java 2 Platform, Enterprise Edition (J2EE) for enterprise software development and deployment. The JRE does not contain tools and utilities such as compilers or debuggers for developing applets and applications.
Java Development Kit (JDK)
The JDK is a superset of the JRE, and contains everything that is in the JRE, plus tools such as the compilers and debuggers necessary for developing applets and applications. The conceptual diagram above illustrates all the component technologies in Java SE platform and how they fit together.

Java SE API

The Java SE application programming interface (API) defines the manner by which an applet or application can make requests to and use the functionality available in the compiled Java SE class libraries. (The Java SE class libraries are also part of the Java SE platform.)
The Java SE API consists of core technologies, Desktop (or client) technologies, and other technologies.
  • Core components provide essential functionality for writing powerful enterprise-worthy programs in key areas such as database access, security, remote method invocation (RMI), and communications.
  • Desktop components add a full range of features to help build applications that provide a rich user experience – deployment products such as Java Plug-in, component modeling APIs such as JavaBeans, and a graphical user interface.
  • Other components round out the functionality.
Java Virtual Machine
The Java Virtual Machine is responsible for the hardware- and operating system-independence of the Java SE platform, the small size of compiled code (bytecodes), and platform security.
Java Platform Tools
The Java SE platform works with an array of tools, including Integrated Development Environments (IDEs), performance and testing tools, and performance monitoring tools.

Java EE Overview

The Java 2 Platform, Enterprise Edition (J2EE) defines the standard for developing multitier enterprise applications. The J2EE platform simplifies enterprise applications by basing them on standardized, modular components, by providing a complete set of services to those components, and by handling many details of application behavior automatically, without complex programming.

The J2EE platform takes advantage of many features of the Java 2 Platform, Standard Edition (J2SE), such as "Write Once, Run Anywhere" portability, JDBC API for database access, CORBA technology for interaction with existing enterprise resources, and a security model that protects data even in internet applications. Building on this base, the Java 2 Platform, Enterprise Edition adds full support for Enterprise JavaBeans components, Java Servlets API, JavaServer Pages and XML technology. The J2EE standard includes complete specifications and compliance tests to ensure portability of applications across the wide range of existing enterprise systems capable of supporting the J2EE platform. In addition, the J2EE specification now ensures Web services interoperability through support for the WS-I Basic Profile.
The J2EE specification also supports emerging Web Services technologies through inclusion of the WS-I Basic Profile . WS-I Basic Profile compliance means that the developers can build applications on the J2EE platform as Web services that interoperate with Web services from non-J2EE compliant environments.

With simplicity, portability, scalability, and legacy integration, the J2EE platform is the platform for enterprise solutions.

For more info
                    Source(J2SE) sun.com
                    Source(J2EE) sun.com

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