Question: What makes J2EE suitable for distributed multitiered Applications?
Answer:The J2EE platform uses a multitiered distributed application model and application logic is divided into components according to function.
The various application components that make up a J2EE application are installed on different machines depending on which tier the
multitiered J2EE environment application component belongs.
The J2EE application parts are:
Client-tier components run on the client machine.
Web-tier components run on the J2EE server.
Business-tier components run on the J2EE server.
Enterprise information system (EIS)-tier software runs on the EIS server.
Question:What is J2EE?
Answer: J2EE is an environment for developing and deploying enterprise applications.The J2EE platform consists of
a set of services,
application programming interfaces (APIs), and
that provide the functionality for developing multitiered, web-based applications.
Question: What are the components of J2EE application?
Answer: A J2EE component is a self-contained functional software unit that is assembled into a J2EE application with its related classes and files and communicates with other components.
The J2EE specification defines the following J2EE components:
The Application client and Java applets represent the client components.
Java Servlet and JavaServer Pages technology components are classified as web components.
Enterprise JavaBeans components (enterprise beans) are business components. They reside on the EJB tier (busines logic tier).
Resource adapter components provided by EIS and tool vendors.
Question:What do Enterprise JavaBeans components contain?
Answer:Enterprise JavaBeans components contain business code, which represents algorithms and workflow.
This logic solves or meets the needs of a particular business domain such as
is handled by enterprise beans running in the business tier (EJB Tier).
All the business code is contained inside an Enterprise Bean which receives data from client programs, processes it (if necessary), and sends it to the (EIS Tier) enterprise information system tier for storage.
An enterprise bean also retrieves data from storage, processes it (if necessary), and sends it back to the client program.
Question: Is J2EE application only a web-based?
No, It depends on type of application that client wants.
A J2EE application can be web-based or non-web-based. if an application client executes on the client machine, it is a non-web-based J2EE application.
The J2EE application can provide a way for users to handle tasks such as J2EE system or application administration.
It typically has a graphical user interface created from Swing or AWT APIs, or a command-line interface.
When user request, it can open an HTTP connection to establish communication with a servlet running in the web tier.
Question:Are JavaBeans J2EE components? Answer:
No. JavaBeans components are not considered J2EE components by the J2EE specification.
They are written to manage the data flow between an application client or applet and components running on the J2EE server or between server components and a database.
JavaBeans components written for the J2EE platform have instance variables and get and set methods for accessing the data in the instance variables.
JavaBeans components used in this way are typically simple in design and implementation, but should conform to the naming and design conventions
outlined in the JavaBeans component architecture.
Question: Is HTML page a web component? Answer: No. Static HTML pages and applets are bundled with web components during application assembly, but are not considered web components
by the J2EE specification. Even the server-side utility classes are not considered web components, either.
Question: What can be considered as a web component?
Answer: J2EE Web components can be either servlets or JSP pages. Servlets are Java programming language classes that dynamically process requests and
construct responses. JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content.
Question: What is the container? Answer: Containers are the interface between a component and the low-level platform specific functionality that supports the component.
Before a Web, enterprise bean, or application client component can be executed, it must be assembled into a J2EE application and deployed into its container.
Question:What are container services? Answer:
A container is a runtime support of a system-level entity. Containers provide components with services such as lifecycle management, security, deployment, and threading.