GoF J2EE Design Patterns

1. @Diego
Thanh
Nguyen
-­‐
http://free.smartbiz.vn
J2EE
DESIGN
PATTERN
10/8/12
www.smartbiz.vn
1

2. Table
Of
Content
q I.
GoF
Design
Pattern
v I.1.
Creation
Patterns
v I.2.
Structural
Patterns
v I.3.
Behavioral
Patterns
q II.
J2EE
Presentation:
q III.
J2EE
Business:
q IV.
J2EE
Integration
10/8/12
www.smartbiz.vn
2

3. I.
How
Design
Patterns
Arise
?
Pattern
1.
Context
Problem
a design situation giving rise to a design problem
Problem
a set of forces occuring in that context
Solution
2.
Context
a form or rule that can be applied to resolve these forces
Forces
IF
you
Nind
yourself
in
CONTEXT
3.
for
example
EXAMPLES,
Solution
with
PROBLEM,
entailing
FORCES
THEN
for
some
REASONS,
apply
DESIGN
FORM
AND/OR
RULE
BeneFits
Consequences
to
construct
SOLUTION
Related
Patterns
leading
to
NEW
CONTEXT
&
OTHER
PATTERNS
10/8/12
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3

4. I.
Design-­‐Pattern
Catalog
! ! Purpose!
Creational! Structural! Behavioral!
Class! • Factory!Method! • Adapter! • Interperter!
• Singleton! • Façade! • Observer!
• Factory! • Decorator! • Command!
• Abstract!Factory! • Composite! • Iterator!
Scope! • Builder! • Adapter! • Chain!of!Responsibility!
Object! • Prototype! • Bridge! • Mediator!
• Object!Pool! • Flyweight! • Momento!
• Proxy! • State!
• Strategy!
• Visitor!
!
! Defer
object
creation
to
Describe
algorithms
and
another
object
Nlow
control
Describe
ways
to
assemble
objects
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5. I.1.
Creation
Patterns
q Creational
Patterns
prescribe
the
way
that
objects
are
created.
These
patterns
are
used
when
a
decision
must
be
made
at
the
time
a
class
is
instantiated.
q Singleton:
ensure
a
class
has
one
Instance,
and
provide
a
global
point
of
access
to
it.
q Abstract
Factory:
provide
an
interface
for
creating
families
of
related
or
dependent
objects
without
specifying
their
concrete
classes.
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6. I.1.1
Abstract
Factory
q Intent:
create
families
of
related
objects
without
specifying
subclass
names
q Applicability:
when
clients
cannot
anticipate
groups
of
classes
to
instantiate
q Concrete
factories
create
groups
of
strategies
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7. I.2.
Structural
Patterns
q Structural
Patterns
prescribe
the
organization
of
classes
and
objects.
q Adapter
v
Convert
the
interface
of
a
class
into
another
interface
that
clients
expect
v
Adapter
lets
classes
work
together
that
couldn’t
otherwise
because
of
incompatible
interfaces
q Decorator
v
Extend
the
functionality
of
the
original
class
in
a
way
that
is
transparent
to
the
client
class
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8. I.2.1.
Composite
q Intent
v treat
individual
objects
&
multiple,
recursively-­‐
composed
objects
uniformly
q Applicability
v Objects
must
be
composed
recursively,
v and
no
distinction
between
individual
&
composed
elements,
v and
objects
in
structure
can
be
treated
uniformly
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9. I.2.1.
Composite
q CORBA
Naming
Service
example
using
CosNaming::BindingIterator
(which
is
an
example
of
the
“Batch
Iterator”
pattern
compound
from
POSA5)
Composite
Node
Leaf
Node
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10. I.3.
Behavioral
Patterns
q Behavioral Patterns prescribe the way
objects interact with each other. They help
make complex behavior manageable by
specifying the responsibilities of objects and
the ways they communicate with each other.
q State:
allow
an
object
to
alter
its
behavior
when
its
internal
state
changes
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11. I.3.1.
Strategy
q Intent
v deNine
a
family
of
algorithms,
encapsulate
each
one,
&
make
them
v interchangeable
to
let
clients
&
algorithms
vary
independently
q Applicability
v When
object
is
conNigurable
with
one
of
many
algorithms,
v and
all
algorithms
can
be
encapsulated,
v and
one
interface
covers
all
encapsulations
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12. I.3.1.
Strategy
q Strategy
applied
in
distributed
(middleware)
Hook
for
marshaling
Hook
for
strategy
the
request
demuxing
Hook
for
the
event
strategy
demuxing
strategy
Hook
for
the
Hook
for
the
connection
concurrency
management
strategy
strategy
Hook
for
the
underlying
transport
strategy
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13. I.3.1.
Oracle
Fusion
Component
OracleFusion Groupware API: A unified interface for all connectors that
access the groupware servers via WebDAV, applying Singleton, Façade and
Factory design patterns
All connectors utilize the Jakarta
EnterConnect Groupware API
Jackrabbit (client-side) API to
send requests to and receive
Exchange OpenGroupware Lotus Domino responses from a variety of
Connector Connector Connector WebDAV-enabled groupware
servers MS Exchange 2003
Email
Jakarta Slide API
WebDAV Server
XML HTTP request Calendar
Jakarta Commons HTTP Client JDOM (JSR 102)
Contact
XML HTTP response
Jakarta Commons Logging Java Transaction API Task
Uploaded
Document
Jakarta Jackrabbit re-uses some of open source libraries such as the
Jakarta Commons library (HTTP Client &Logging), JDOM (JSR 102), JTA, JMX, …
13

14. I.3.2.
OF
Design
Pattern
q Singleton:
the
Connector
class
must
only
have
one
instance
because
it’s
wasteful
&
useless
to
keep
several
instances
on
memory.
Keeping
so
many
connectors
will
difNicult
to
manage
lifecycle
&
impact
the
performance
of
application.
q Factory
Method:
because
of
we
assume
our
API
can
be
used
against
multiple
servers
so
that
there
must
be
a
Connector
for
each
server
(i.e.
ECExchangeConnector,
ECLotusDominoConnector,
ECOpenGroupwareConnector).
Each
connector
is
responsible
for
manufacturing
its
own
managers
(MailManager,
CalendarManager,
TasksManager)
and
delegate
the
jobs
to
them.
The
connector
will
only
be
determined
by
the
client
depending
on
the
conNiguration.
v For
example,
if
a
client
(portlet)
need
to
send
a
mail
by
Exchange
server
then
it
will
call
the
ECExchangeConnector;
this
connector
then
will
use
its
localized
manager
ExchangeMailManager
to
make
life
easier.
q Abstract
Factory:
ECGroupwareFactory
is
the
abstract
factory
class
for
all
connectors
because
it
will
expose
a
uniFied
interface
for
connectors
to
client.
q Facade:
the
uniFied
interface
will
be
deFined
in
the
Façade
pattern.
As
stated
before,
a
speciNic
Connector
will
delegate
the
appropriate
jobs
to
its
subsystems
(managers).
The
façade
pattern
also
decouples
the
managers
from
the
client
and
other
managers,
thereby
promoting
independence
and
portability.
10/8/12
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15. I.3.1.
OF
Design
Pattern
<<Factory Method>>
«interface»
TasksManager
<<Abstract Factory>>
ECGroupwareFactory
<<Façade>>
ExchangeTasksManager
<<Singleton>>
ECLotusDominoConnector ECOpenGroupwareConnector ECExchangeConnector ExchangeCalendarManager
ExchangMailManager
«interface» «interface»
MailManager CalendarManager
Apache Slide Class
15
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16. I.4.1.
Observer
Pattern
q Easier
to
keep
a
consistent
and
maintainable
view
of
the
data
v Half
as
many
connections
between
actions,
views
v Views
are
independent
and
unaware
of
each
other
Data
Action
Action
Action
Action
Action
Action
Action
Action
View
à
View
&
Action
à
Data
notiNies
observers
via
events
View
Messages
about
the
data
when
the
state
of
the
data
changes
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17. I.4.2.
Implementing
an
Observer
1. Assign
the
subject
to
the
observers
(MainForm_Load)
IssueSubject
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18. I.4.3.
Implementing
an
Observer
1. Assign the subject to the
observers (MainForm_Load)
m_subject = new IssueSubject()
paneA.Subject = m_subject
b paneB.Subject = m_subject ...
c d
a
IssueSubject
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19. I.4.4.
Implementing
an
Observer
1. Assign the subject to the
observers (MainForm_Load)
m_subject = new IssueSubject()
paneA.Subject = m_subject
b paneB.Subject = m_subject ...
c d 2. Observers bind and save
changes to Subject.DataSet
a
IssueSubject
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20. I.4.5.
Implementing
an
Observer
1. Assign
the
subject
to
the
observers
(MainForm_Load)
m_subject
=
new
IssueSubject()
paneA.Subject
=
m_subject
paneB.Subject
=
m_subject
...
b
c
d
2. Observers
bind
and
save
changes
to
Subject.DataSet
a
3. When
data
changes,
subject
raises
DataChanged
event
IssueSubject
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21. I.4.6.
Implementing
an
Observer
1. Assign
the
subject
to
the
observers
(MainForm_Load)
m_subject
=
new
IssueSubject()
paneA.Subject
=
m_subject
b
paneB.Subject
=
m_subject
...
c
d
2. Observers
bind
and
save
changes
to
Subject.DataSet
a
3. When
data
changes,
subject
raises
DataChanged
event
4. Observers
handle
subject
events
to
rebind
data,
if
IssueSubject
they
care
m_subject.DataChanged
+=
…
‘
rebind
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22. I.5.1.
Coordinate
Command
State
q Related
menu
and
toolbar
widgets
are
not
automatically
handled
together
q Command
Pattern
v Command
objects
unify
the
state
and
action
for
related
UI
widgets
q Example:
v “Save”
action
Ø Menu
item
Ø Toolbar
button
Ø Context
menu
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23. I.5.2.
Implementing
a
Command
1. Create
a
Command
for
each
action
in
MainForm_Load()
action
=
new
Command.Action(this.WorkOfNline_Action)
ofNlineCommand
=
new
Command(action)
2. Wire
menu
items
and
toolbar
buttons
to
the
Command
using
Commander
objects
MenuItemCommander.Connect(menuWorkOfNline,
ofFlineCommand
)
ToolBarButtonCommander.Connect(tlbOfNline,
ofFlineCommand
)
3. Control
button
and
menu
item
state
through
the
Command
'
Disable
all
UI
widgets
connected
to
this
command
ofNlineCommand.IsEnabled
=
false
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24. I.6.1.
Accelerated
J2EE
Development
q Architect
Service-­‐Oriented
Components
v Design
for
Flexible,
Agile
Applications
and
Iterative
Development
q Apply/Extend
Pre-­‐Built
COTS
Components
v Infrastructure
and
Common
Business
Components
q Generate/Extend
Custom
Components
v Rapidly
Specify
and
Provision
New
Components
q Leverage
Industry
Development
Standards
v Frameworks
(STRUTS,
Spring
/
Weld,
Hibernate)
v Patterns
(MVC)
v XML,
Best
Practices
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25. II.
J2EE
Application
Design
Patterns
Business
Logic
&
Data
Integration
Presentation
Messaging
Fabric
&
Persistence
EJB
Container
EJB
Container
Response
8.
Execute
Business
Resources
Biz
Method
13.
Request
Service
14.
CRUD
Facade
10b.
Data
Data
Query
9.
Get/Set
Access
Database
<<de-­‐serialize>>
Web
Server
&
18.
Response
Assemble
Remove
Object
Serialized
RMI
JMS
Servlet
Engine
Value
Data
Directory
Object
16.
Forward
JSF,
JSP
JMS
(Taglibs)
<<creates>>
Value
12.
1.
Request
Object
Get/Set
17.
State?
Assembler
<<uses>>
Action
Remove
Data
Servlet
10a.
Access
<<uses>>
Invoke
Proxy
4.
Dispatch
2.
Fill
State
Data
XML
11.
Entity
Connection
3.
Validate
CRUD
Connection
Action
to
Bean
Pool
(Stateless)
Data
Factory
Form
&
Value
Session
Forward
<<uses>>
Object
Bean
Mappings
Action
Form
5.
Get
Delegate
Action
Object
15.
Fill
State
<<uses>>
Key
Other
Infrastructure
6.
Execute
<<supplies>>
RMI
Business
Business
<<uses>>
EJB
Container
Value
Model
Delegate
Delegate
M
JMS
Object
Pattern
Factory
Adapter
7a.
Event
Security
Messaging
Event
Execute
View
Interceptor
Management
Command
NotiFication
Biz
Method
Business
V
Pattern
Framework
Framework
Factory
Framework
Service
Proxy
<<uses>>
Controller
C
Pattern
<<uses>>
7b.
CRUD
Data
Data
Message
Q
Filter
Service
Access
&
Channel
Other
Interceptors
Activation
Proxy
To
DAO
P
Pattern
Locator
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26. II.
Model-­‐View-­‐Controller
–
Passive
:Controller :Model :View
handleEvent
service
update
getData
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27. II.
Model-­‐View-­‐Controller
–
Active
Controller
<<interface>>
Observer
Model
+update()
View
:Model :View
handleEvent
notify
update
getData
data
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28. II.1.
Presentation
Tier
Patterns
q Intercepting
Filter
q Front
Controller:
Use
of
a
Controller
to
handle
all
web
requests
q Dispatcher
View:
The
controller
works
with
a
Dispatcher
that
handles
navigation
q Composite
View
q View
Helper
q Service
to
Worker
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29. II.2.
Intercepting
Filter
q Problems:
v Verify
authentication
v Check
type
of
client
v Is
the
session
valid?
q Solution:
implement
one
or
more
Intercepting
Nilters.
q Sample:
Filter-­‐servlet
-­‐
can
transparently
pre
and
post
process
all
requests
in
an
unlimited
length
Nilter
chain.
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30. II.3.
Front
Controller
&
Dispatcher
q Front
Controller
-­‐
Problems:
v Multiple
views.
v Navigation
logic
embedded
in
views.
v DifNicult
to
maintain
view
logic
as
application
grows.
v Want
to
reuse
view
navigation
within
multiple
clients.
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31. II.3.
Front
Controller
-­‐
Dispatcher
Client FrontController Dispatcher Vi ew Helper
1: Send Request
1.1: Delegate Request
1.1.1: Forward Request
2: Send Request
2.1: Forward Request
3: Send Request
3.1: Process Request
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32. III.4.
View
Helper
q Problem:
v Many
common
operations
in
each
view.
v Often
view
output
is
dependant
on
business
data.
v Create
more
cohesive
look
and
feel.
v Like
to
hand
off
UI
to
web
design
group
q Solution:
v Basically
anything
that
helps
you
display
your
model
data
in
a
reusable
fashion.
v Implemented
as
JavaBeans,
Tags
or
XML/XSLT
q See
the
JSTL,
JSF
and
Struts.
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33. II.5.
Composite
View
q Problem:
v Many
common
&
recurring
components
in
a
view.
v Fragments
may
display
differently
given
user
type
(i.e.
faculty,
student).
v Look
and
feel
in
Nlux
needs
to
be
easily
updateable.
q Differs
from
View
Helper
as
the
Composite
View
decides
which
sub-­‐views
to
include
while
View
Helper
generally
decides
how
to
display
a
given
sub-­‐view.
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34. III.
Business
Tier
Patterns
q Business
Delegate:
use
of
a
Business
Delegate
to
hide
Implementation
Detail.
q Session
Façade
q Service
Locator
q Value
Object
q Composite
Entity
q Value
Object
Assembler
q Value
List
Handler
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35. III.1.
Business
Delegate
Cl ient BusinessService
1: Creat e wi th ID BusinessDelegate
1.1: Convert ID to Handle
Handle
1.1.1: Create
2: Invoke
2.1: Get Business Service
2.1. 1: Connect
2.1. 2: Return Business Service
2.2: Invoke
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36. III.2.
Session
Façade
Pattern
q Problem:
v Need
very
loose
coupling
between
client
and
ever
changing
business
tier.
v Data
tier
changing;
need
to
improve
reuse.
q Session
Bean
EJB Tier
provides
uniNied
approach
q Façade
hides
Entity
Bean
Details
Session
Client Entity Bean
Bean
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37. IV.
Integration
q Data
Access
Object
q Service
Activator
q User
WorkNlow
Integrator
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37

38. IV.1.
Data
Access
Object
Business DataAcces
accesses
Object sObject
inherits inherits inherits
Oracle Sybase
DB2DAO
DAO DAO
adapts adapts adapts
Oracle DB2 Sybase
Database Database Database
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39. 10/8/12
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