Spring AOP

Question 1

What are cross cutting concerns?

Answer 1

Functionalities that are orthogonal to the business requirement and cut across multiple points of application are called cross cutting concerns. Some examples are like Authentication, Authorization, Logging, Metrics, etc.

Question 2

Give example of common cross cutting concerns

Answer 2

Logging, Security, Transaction management

Question 3

What does AOP provide us?

Answer 3

Ability to decouple these cross cutting concerns from main business logic and make the code resuable.

Question 4

Which are various AOP jargons?

Answer 4

1) Aspect
2) Advice
3) Pointcut
4) JoinPoint

Question 5

What is Aspect?

Answer 5

Cross cutting concerns can be modularized into special classes called aspects.

Question 6

What is Advice?

Answer 6

The piece of code that is invoked during program execution. Advice defines both when and what of aspect.

Question 7

What is Joinpoint?

Answer 7

This represents a point in your application where you can plug in AOP aspect. In spring a join point is always a method.

Question 8

What is pointcut?

Answer 8

Pointcuts define the when of aspect. It is an expression which defines filter. This is a set of one or more joinpoints where an advice should be executed.

Question 9

What is weaving?

Answer 9

Weaving is the process of linking the aspets with other application types or objects to create an adviced object. There are two types of weaving.

1) Compile time weaving
2) Runtime weaving.

Question 10

Which expression types are supported when defining pointcut?

Answer 10

1) execution
2) args
3) within
4) this
5) target

Question 11

Define execution expression in pointcut

Answer 11

For matching method execution join points, this is primary pointcut designator what you will use

Question 12

Define args expression in pointcut

Answer 12

Limits matching to joinpoints where the arguments are instances of the given types.

Question 13

Define within expression in pointcut

Answer 13

Limits matching to join points within certain types

Question 14

Define this expression in pointcut

Answer 14

Limits matching to joinpoints where the bean reference is an instance of the given type.

Question 15

Define target expression in joinpoint

Answer 15

Limits matching to joinpoints where the target object is an instance of the given type.

Question 16

Pointcut expression for any method named ‘setData’

Answer 16

@PointCut(“execution(* setData(..))”)

Question 17

Pointcut expression for execution of any method defined by the AccountService class

Answer 17

@Pointcut(“execution(* co.edureka.spring.service.AccountService.*(..)”)

Question 18

Pointcut expression for execution of any method within the controllers package or a sub-package

Answer 18

within(co.edureka.controllers..*)

Question 19

Pointcut expression for execution of any method which takes a single parameter and where the argument passed at runtime is Date

Answer 19

args(java.util.Date)

Question 20

Pointcut expression for execution of any method where the target object implements the TransactionService interface

Answer 20

target(co.edureka.service.TransactionService)

Question 21

How many ways can you do AOP

Answer 21

Spring XML based or AspectJ annotation driven aspects

Question 22

Advice types supported in spring

Answer 22

Before, After, AfterReturning, AfterThrowing, Around

Question 23

Which interface is used to implement Before advice

Answer 23

MethodBeforeAdvice interface and it has before method.

Question 24

Which interface is used to implement After returning advice

Answer 24

AfterReturningAdvice interface is used and it has method afterReturning

Question 25

How to configure advice in spring xml?

Answer 25

Need to declare bean in xml. And then configure ProxyFactoryBean. And in proxy bean need to set property "target" and "interceptorNames"

Question 26

Which interface is used to create Around advice?

Answer 26

MethodInterceptor interface is used. It has invokeMethod and provides MethodInvocation object on which proceed method can be called to execute actual method.

Question 27

Which interface is used to implement After throwing advice?

Answer 27

AfterThrowingAdvice interface is used. it has method afterThrowing

Question 28

AspectJ annotations?

Answer 28

``` @Aspect, @Before, @After, @AfterReturning, @AfterThrowing, @Pointcut ```

Question 29

How to enable aspecj annotations in spring

Answer 29

aop:asjectj-autoproxy tag

Question 30

How to define common pointcut configuration that can be reused at multiple places like multiple advices?

Answer 30

In a common class declare a method and annotate it with @Pointcut annotation and provide pointcut there. Then wherever you want to use the pointcut provide Fully qualified classname.methodname() in @Before, @After etc annotations.

Question 31

Which interface is used to implement After returning advice

Answer 31

AfterReturningAdvice interface is used and it has method afterReturning

Question 32

How to configure advice in spring xml?

Answer 32

Need to declare bean in xml. And then configure ProxyFactoryBean. And in proxy bean need to set property "target" and "interceptorNames"

Question 33

Which interface is used to create Around advice?

Answer 33

MethodInterceptor interface is used. It has invokeMethod and provides MethodInvocation object on which proceed method can be called to execute actual method.

Question 34

Which interface is used to implement After throwing advice?

Answer 34

AfterThrowingAdvice interface is used. it has method afterThrowing

Question 35

AspectJ annotations?

Answer 35

``` @Aspect, @Before, @After, @AfterReturning, @AfterThrowing, @Pointcut ```

Question 36

How to enable aspecj annotations in spring

Answer 36

aop:asjectj-autoproxy tag

Question 37

How to define common pointcut configuration that can be reused at multiple places like multiple advices?

Answer 37

In a common class declare a method and annotate it with @Pointcut annotation and provide pointcut there. Then wherever you want to use the pointcut provide Fully qualified classname.methodname() in @Before, @After etc annotations.