spring boot: Introduction to Aspect

Aspect is a block of code that is injected into application at run time.

In a typical application, application is devided into multiple modules, and each module should handle concerns like logging, security, transactions etc., apart from the business logic.

Aspects are used to solve cross-cutting concerns.

Examples of cross-cutting concerns

a.   Caching

b.   Logging

c.    Transaction Management

d.   Security (Authorization and Authentication)

Key terms in Aspect Oriented Programming

a.   Join Point: It is the line of code that Aspect is going to target (Ex: a method).

b.   Pointcut: It is an expression used to identify the Join Point.

c.    Advice: it is the code that you actually executes at a join point that is selected by Pointcut expression.

d.   Aspect: It is a module that contains all the pointcuts and advices.

Example

@Configuration
@Aspect
public class LoggingAspect {

 @Pointcut("@annotation(com.sample.app.annotations.Loggable)")
 public void executionTimeExpr() {
 }

 @Around("executionTimeExpr()")
 public Object executionTime(ProceedingJoinPoint joinPoint) throws Throwable {
  .....
  .....
  Object result = joinPoint.proceed();
  .....
  .....

  return result;
 }

}

In the above Example,

Aspect: LoggingAspect

Pointcut: executionTimeExpr

Advice: executionTime

JoinPoint: It is the method that matches to given point cut expression.

      Introduction to Aspect

      Aspect: Hello World Application

      Aspects: Before Advice

      Aspect: @After Advice

      Aspects: @Around advice

      Aspect: @Pointcut example

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