Java Reference
In-Depth Information
• New features for Enterprise JavaBeans (EJB) components (see
“
Enterprise
JavaBeans Technology
”
on page
25
for details)
• New features for servlets (see “
Java Servlet Technology
” on page
26
for details)
• New features for JavaServer Faces components (see “
JavaServer Faces Techno-
Java EE Application Model
The Java EE application model begins with the Java programming language and the Java
virtual machine. The proven portability, security, and developer productivity they provide
forms the basis of the application model. Java EE is designed to support applications that
implement enterprise services for customers, employees, suppliers, partners, and others
who make demands on or contributions to the enterprise. Such applications are inherently
complex, potentially accessing data from a variety of sources and distributing applications
to a variety of clients.
To better control and manage these applications, the business functions to support these
various users are conducted in the middle tier. The middle tier represents an environment
that is closely controlled by an enterprise's information technology department. The
middle tier is typically run on dedicated server hardware and has access to the full services
of the enterprise.
The Java EE application model defines an architecture for implementing services as mul-
titier applications that deliver the scalability, accessibility, and manageability needed by
enterprise-level applications. This model partitions the work needed to implement a mul-
titier service into the following parts:
• The business and presentation logic to be implemented by the developer
• The standard system services provided by the Java EE platform
The developer can rely on the platform to provide solutions for the hard systems-level
problems of developing a multitier service.
Distributed Multitiered Applications
The Java EE platform uses a distributed multitiered application model for enterprise ap-
plications. Application logic is divided into components according to function, and the
application components that make up a Java EE application are installed on various ma-
chines, depending on the tier in the multitiered Java EE environment to which the applic-
ation component belongs.
