spring aop.pptx aspt oreinted programmin

SPRING FRAMEWORK
3.0
Aspect Oriented Programming with
Spring Framework -
AOP

What is
AOP?
 is a programming paradigm
 extends OOP
 enables modularization of crosscutting
concerns
 is second heart of Spring Framework

A simple service
method
public Order getOrder(BigDecimal orderId) {
return (Order) factory.openSession()
.get(Order.class, orderId);
}

Add permissions
check
if (hasOrderPermission(orderId)) {
return (Order) factory.openSession()
.get(Order.class, orderId);
} else {
throw new SecurityException("Access Denied");
}
}

Add transaction
management
Order order;
Session session = factory.openSession();
Transaction tx = session.beginTransaction();
try {
order = (Order) session.get(Order.class,
orderId);
tx.commit();
} catch (RuntimeException e) {if (tx!=null)
{tx.rollback();}
} finally {session.close();}
return order;
} else { throw new SecurityException("Access
Denied");}
}

Add
cache
Order order = (Order)cache.get(orderId);
if (order==null) {
Session session = factory.openSession();
Transaction tx = session.beginTransaction();
try {
order = (Order) session.get(Order.class,
orderId);
tx.commit();
cache.put(orderId, order);
} catch (RuntimeException e)
{if (tx!=null)
{tx.rollback();}
} finally {session.close();}
}
return order;
} else { throw new
SecurityException("Access Denied");}
}

A similar problem at enterprise
level

What does AOP
solve?
Logging
Validatio
n
Caching
Security
Transactions
Monitoring
Error
Handling
Etc…

AOP
concepts
 aspect
 advice
 pointcut
 join
point

AOP and
OOP
1. Aspect – code unit that
encapsulates pointcuts,
advice, and attributes
2. Pointcut – define the set
of entry points (triggers)
in which advice is
executed
3. Advice –
implementation of
cross cutting concern
4. Weaver – construct
code
(source or object) with
1. Class – code unit that
encapsulates methods
and attributes
2. Method signature – define
the entry points for the
execution of method
bodies
3. Method bodies –
implementation of the
business logic concerns
4. Compiler – convert source
code
to object code
AOP OOP

AOP
concepts(2)
 introduction
 target
object
 AOP proxy
 weaving
 compile
time
 load time
 runtime

Spring
AOP
 implemented in pure java
 no need for a special compilation
process
 supports only method execution join
points
 only runtime weaving is available
 AOP proxy
 JDK dynamic proxy
 CGLIB proxy
 configuration
 @AspectJ annotation-style
 Spring XML configuration-style

Declaring
aspect
@Aspect
public class EmptyAspect {
}

<aop:aspectj-autoproxy proxy-target-class="false | true"/>
<bean
class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator">
</bean>
<bean class="example.EmptyAspect"/>

Pointcut
designators
 code
based
 execution
 within
 target
 this
 args
 bean

Pointcut
designators(2)
 annotation
based
 @annotation
 @within
 @target
 @args

Format of an execution
expression
execution(
modifiers-pattern
returning-type-pattern
declaring-type-pattern
name-pattern(param-
pattern)
throws-pattern
)

Simple pointcut
expressions
@Aspect
public class ItemStatusTracker {
@Pointcut("execution(* approve(..))")
public void ifApprove() {}
@Pointcut("execution(* reject(..))")
public void ifReject() {}
@Pointcut("ifApprove() || ifReject()")
public void ifStateChange() {}
}

Execution
examples
any public method
execution(public * * (..))"
any method with a name beginning with
"get"
execution(* get*(..))
any method defined by the appropriate
interface
execution(* bank.BankService.*(..))
any method defined in the appropriate
package
execution(* com.epam.pmc.service.*.*(..))
other examples
http://static.springsource.org/spring/docs/3.0.x/spring-fra

Advic
e
 associated with a pointcut
expression
 a simple reference to a named
pointcut
 a pointcut expression declared in
place
 runs
 before
 after returning
 after throwing
 after (finally)

Before
advice
@Aspect
public class BankAspect {
@Pointcut("execution(public * * (..))")
public void anyPublicMethod() {}
@Before("anyPublicMethod()")
public void logBefore(JoinPoint joinPoint) {
//to do something
}
}

After returning
advice
@Aspect
@AfterReturning( pointcut="executio
n(* get*(..))",
returning="retVal")
public void logAfter(JoinPoint
joinPoint, Object retVal) {
//to do something
}
}

After throwing
advice
@Aspect
@AfterThrowing(
pointcut = "execution(* bank..*ServiceImpl.add*(..))",
throwing = "exception")
public void afterThrowing(Exception exception) {
//to do something
}
}

After finally
advice
@Aspect
@Pointcut("execution(public * * (..))")
public void anyPublicMethod() {}
@After(value="anyPublicMethod() && args(from, to)")
public void logAfter(JoinPoint jp, String from, String to) {
//to do something
}
}

Around
advice
@Aspect
public class BankCacheAspect {
@Around("@annotation(bank.Cached)")
public Object aroundCache(ProceedingJoinPoint joinPoint){
//to do something before
Object retVal = joinPoint.proceed();
//to do something after
}
}

Aspect and advice
ordering
 order of advice in the same aspect
 before
 around
 after finally
 after returning or after throwing
 Spring interface for ordering aspects
 org.springframework.core.Ordered
 Spring annotation
 org.springframework.core.annotation.O
rder

Declaring an
aspect
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http
://www.w3.org/2001/XMLSchema-instance" xmlns:aop=
"http://www.springframework.org/schema/aop"
xsi:schemaLocation="…">
<aop:config>
<aop:aspect id="bankAspectId" ref="bankAspect">
<aop:pointcut id="anyPublicMethod"
expression="execution(public * *
(..))"/>
<aop:before pointcut-ref="anyPublicMethod"
method="logBefore"/>
</aop:aspect>
</aop:config>
<bean id="bankAspect" class="bank.BankAspect"/>
</beans>

Bean in Spring
container
Standard OOP implementation Implementation with AOP

AOP
proxies
Invoke directly Invoke via proxy

Introduction behaviors to
bean
@Aspect
public class CalculatorIntroduction {
@DeclareParents(
value = "calculator.ArithmeticCalculatorImpl",
defaultImpl = MaxCalculatorImpl.class)
public MaxCalculator maxCalculator;
@DeclareParents(
value = "calculator.ArithmeticCalculatorImpl",
defaultImpl = MinCalculatorImpl.class)
public MinCalculator minCalculator;
}

Introduction states to
bean
@Aspect
public class BankServiceIntroductionAspect {
@DeclareParents(
value="bank.BankServiceImpl",
defaultImpl=DefaultCounterImpl.class)
public Counter mix;
@Before("execution(* get*(..)) &&
this(auditable)")
public void useBusinessService(Counter auditable) {
auditable.increment();
}
}

Spring AOP vs
AspectJ
 no need for a
special compilation
process
 support only
method execution
pointcuts
 advise the
execution of
operations on
 need AspectJ
compiler or setup
LTW
 support all pointcuts
 advice all
domain objects
Spring AOP AspectJ

@AspectJ vs
XML
 has more
opportunities, such
as combine named
pointcuts
 encapsulate the
implementation of the
requirement it
addresses in a single
place
 can be used with
any JDK level
 good choice to
configure
enterprise
services
@AspectJ XML

Link
s
 Useful links
 Wiki: Aspect-oriented programming
http://en.wikipedia.org/wiki/Aspect-oriented_program
ming
 Spring Reference
http://static.springsource.org/spring/docs/3.0.x/sp
ring-
framework-reference/html/aop.html
 AspectJ home site
http://www.eclipse.org/aspectj/
https://www.jbktutorials.com/spring-aop/types-

spring aop.pptx aspt oreinted programmin

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