Introduction to J2EE

hopeacceptableSoftware and s/w Development

Oct 28, 2013 (3 years and 7 months ago)

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Introduction to J2EE

Yang Song:

28243494

Nengping Wei:
75165080



Java classification:



J2SE

J2SE stands for Java 2 standard edition and is normally for
developing desktop applications, forms the core/base API
. We
mainly using J2SE for our college projects.



J2EE

J2EE stands for Java 2 enterprise edition for applications which
run on servers,
like the
web sites
.



J2ME

J2ME stands for Java 2 micro edition for applications which run
on resource constrained devices (small scale devices) like cell
phones,
like
games.

What

is

J
2
EE?



Java Platform, Enterprise
Edition



The
J2EE platform extended from J2SE, it provides
an API
and runtime environment for developing and running
enterprise software, including network and web services, and
other large
-
scale, multi
-
tiered, scalable, reliable, and secure
network applications
.






Why

J
2
EE?

1
st
,

Specifications:



J2EE includes several API specifications, such as JDBC,
RMI, e
-
mail, JMS, web services, XML, etc., and defines how
to coordinate them.



J2EE features some specifications unique to Java EE for
components. These include Enterprise JavaBeans, Connectors,
servlets,
Java Server
Pages and several web service
technologies. This allows developers to create enterprise
applications that are portable and scalable, and that integrate
with legacy technologies.









Why

J
2
EE
?

2
nd
,

Enterprises software development:


Problems need to be solved:


Distribution / Portability

/ Web
-
Oriented

/ Easy
to
maintain /
Easy
to
extend / Concurrency

/ Security


J2EE provides:


A

distributing, portable developing architecture.


S
tandard
API for web development


It simplifies
the design for
middleware server




Why J2EE
?

3
rd
: Developers
and
users:



less developing time
consumption



re
-
useable unit, JSP,
EJP



much simpler connections: XML, JDBC,
RMI
-
IIOP

Software development process:

Most applications before J2EE consisted of 3 different parts
:



User Interface: Presentation
Tier



Application Logic: Business Logic
Tier



Data Access: Data Access Tier


Software development process:

Below
is a diagram showing the changing about how we
develop a software
application:








E
arliest:
We develop those three parts together.

1
Tier


Then: UI and AL together, Data Access part alone

2
Tiers


Then:
All apart together





3
Tiers


Now: M
ultiple
Application Logic or Data Access

N
Tiers


J2EE
N
-
tier:

J2EE
platform is a multi
-
tiered system.

A
tier is a logical or functional partitioning of a system.

The
advantages of a 3
-
tiered or n
-
tiered application:

3
-
tier or
multi
-
tier architectures force separation among presentation
logic, business logic and database logic. Let us look at some of
the key benefits:


Manageability
:

Each tier can be monitored, tuned and
upgraded independently and different people can have clearly
defined responsibilities.


Scalability
: More hardware can be added and allows
clustering (i.e. horizontal scaling).


Maintainability
: Changes and upgrades can be performed
without affecting other components.


Availability
: Clustering and load balancing can provide
availability.


Extensibility
: Additional features can be easily added.



J2EE N
-
tier
:

Each
tier is assigned a unique responsibility in a 3
-
tier system.
Each tier is logically separated and loosely coupled from each
other, and may be distributed
.



Client tier




Presentation tier




Business tier




Integration tier




Resource tier




J2EE N
-
tier:


Critical Technology of
J2EE:

EJB


Enterprise JavaBeans (EJB) is a managed, server
-
side
component architecture for modular construction of enterprise
applications
.



The EJB specification intends to provide a standard way to
implement the back
-
end 'business' code typically found in
enterprise applications (as opposed to 'front
-
end' interface
code).



General responsibilities of
EJB:



Execution:



Transactions:





Critical Technology of J2EE:

CORBA


The Common Object Request Broker Architecture (CORBA)
is a standard defined by the Object Management Group
(OMG) that enables software components written in multiple
computer languages and running on multiple computers to
work together (i.e., it supports multiple platforms
).



CORBA enables separate pieces of software written in
different languages and running on different computers to
work with each other like a single application or set of
services.



Critical Technology of J2EE:

JSP


Java Server
Pages (JSP) is a technology that helps software
developers create dynamically generated web pages based on
HTML, XML, or other document types. Released in 1999 by
Sun Microsystems,[1] JSP is similar to PHP, but it uses the
Java programming language.



Some comparison and
clarification:



JSP vs. ASP



Java Servlet vs. JSP

Thank you for listening!