1. A O P & IO C
V u Co n g T h a n h
V i Qu o c Ha n h
Social team
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2. Agenda
W h a t is IO C ?
IO C – Tim e o f In je c t o r
IO C – P r o s & C o n s
IO C - S c o p e
De mo
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3. In v e r s io n O f
C o n t r o l ( IO C )
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5. Implementation with NOT IOC
» Construction by Hand.
» Factory Pattern.
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6. Dependencies Problems
» Code is tightly coupled
» Difficult to isolate when testing
» Difficult to maintain.
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7. What is IOC?
» Hollywood principle “Don't call us, we'll call you.”
» Creating, Assembling and Wiring the dependencies into
Object graph.
» Type of Dependency Injector:
– Constructor
– Setter
– Method
– Field(Guice)
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8. IOC: Pros and Cons
» Pros:
– Loosely Coupled
– Increases Tesability
– Separates component clearly.
– Allows for use of Inversion of Control Container.
» Cons:
– Increases code complexity
– Difficult to understand at First
– Complicate Debugging at First
– Complicates following Code Flow.
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9. Time for Injector - BoorStrapping the Injector
» Constructed and prepared before
it can be used.
– In the init lifecycle stage of a
web application.
– On startup of a desktop
program
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10. IOC - Metadata and Injector Configuration
» XML configuration file.
» Annotations(@Injector, @Singleton, …)
» Invoking into a programmatic API.
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11. Boorstrapping the Injector(Cont)
» Constructed and prepared before
it can be used.
– On demand, every time it is
needed
– Lazily, when it is first needed
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12. IOC - What is Scope?
Fixed duration of time or method calls in which an object
exist. General-purpose scopes: Singleton and No-scope.
» Web Application:
– Request, Session and Conversation scope
– Transaction scope
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13. IOC - Benefit of Scope
» Lets injector manage the latent state of your objects
» Ensures that your services get new instances of
dependencies as needed
» Implicitly separates state by context.
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17. What?
AOP
- Enables encapsulation of functionality that affects multiple
classes in separate
units
- Complements object oriented programming
- Is not about “patching” pieces of code. About performing an
action
systematically upon recognition of a behavior in the code.
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18. Why?
Benefits:
- Separates persistence and specific functionality (logging,
security...)
- Promotes code reuse and modularization
- Decouples codes (the LogFactory from the DAO impl’s)
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19. AOP vs OOP
Object Oriented Aspect Oriented
Class – code unit that Aspect – code unit that
encapsulates methods and encapsulates pointcuts, advice,
attributes. and attributes.
Method signatures – define Pointcut – define the set of
the entry points for the entry points (triggers) in which
execution of method bodies. advice is executed.
Method bodies – Advice – implementations of the
implementations of the cross cutting concerns.
primary concerns.
Compiler – converts source Weaver – instruments code
code into object code. (source or object) with advice.
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20. Concepts
- Crosscutting Concerns
- Aspect: The merger of advice and pointcuts.
All information about where, when and what
job is to be done.
- Advice: The job of an aspect. Defines the what
and when of an aspect.
- Pointcut: Pointcuts help narrow down the
joinpoints advised by an aspect. Define the
where of an aspect.
- Joinpoint: A point in the execution of an
application where an aspect can be plugged
in. All the opportunities for advice to be
applied.
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21. Concepts
- Target: Object being advised.
- Proxy: The object created after applying advice to the target object. To the client
making use of the target object the proxy looks the same.
- Weaving: Process of applying aspects to a target object to create a new, proxied
object.
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22. How it works?
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24. Th a n k yo u !
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Notes de l'éditeur
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