J2EE study(二)-----J2EE Components

A J2EE Components is a self-contained functional software unit that is assembled into to a J2EE application with its related classes and files and that communicates with other components.

The J2EE specification defines the following J2EE Application:

Application clients and applets are components that run on the client

Java Servlet and JSP technology components are web components that run on the server

EJB components are business components that run on the server

The difference between J2EE Components and Standard Java Classes is that J2EE components are assembled into J2EE application,are verified to be well formed and in compliance with the J2EE specification, and are deployed to production, where they are run and managed by the J2EE Server

A J2EE Client can be a web client and application client

Web client consists of two parts:

dynamic web pages containing various types of markup language,which are generated by the web components running in the web tier

a web browser ,which renders the web pages received from the server

Application Client

An application client runs on a client machine and provides a way for users to handle tasks that require a richer user interface than can be provided by a markup language. It typically has a graphical user interface (GUI) created from the Swing or the Abstract Window Toolkit (AWT) API, but a command-line interface is certainly possible.