Spring AOP

AOP concepts

Aspect: a modularization of a concern that cuts across multiple classes.
Transaction management is a good example of a crosscutting concern in enterprise Java applications.
In Spring AOP, aspects are implemented using regular classes (the schema-based approach) or
regular classes annotated with the @Aspect annotation (the @AspectJ style).

Join point: a point during the execution of a program, such as the execution of a method or the handling of an exception.
In Spring AOP, a join point always represents a method execution.

Advice: action taken by an aspect at a particular join point.
Different types of advice include "around," "before" and "after" advice.
(Advice types are discussed below.) Many AOP frameworks, including Spring, model an advice as an interceptor,
maintaining a chain of interceptors around the join point.

Pointcut: a predicate that matches join points. Advice is associated with a pointcut expression and
runs at any join point matched by the pointcut (for example, the execution of a method with a certain name).
The concept of join points as matched by pointcut expressions is central to AOP, and
Spring uses the AspectJ pointcut expression language by default.

Types of advice:
Before advice: Advice that executes before a join point, but which does not have the ability to prevent execution flow proceeding to the join point (unless it throws an exception).

After returning advice: Advice to be executed after a join point completes normally:
for example, if a method returns without throwing an exception.

After throwing advice: Advice to be executed if a method exits by throwing an exception.

After (finally) advice: Advice to be executed regardless of the means by which a join point exits (normal or exceptional return).

Around advice: Advice that surrounds a join point such as a method invocation. This is the most powerful kind of advice. Around advice can perform custom behavior before and after the method invocation. It is also responsible for choosing whether to proceed to the join point or to shortcut the advised method execution by returning its own return value or throwing an exception.

Annotation on Aspect Class 
@AspectJ


All advice Annotation
@Around
@After
@Before
@AfterReturning
@AfterThrowing

ForExample

@Before("execution(* com.bebo.dao.EmployeeDao.*(..))")

pom.xml

<!-- Spring AOP + AspectJ -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>4.3.11.RELEASE</version>
</dependency>

<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.6.11</version>
</dependency>

<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.6.11</version>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>1.7.12</version>
</dependency>

EmployeeAspect .java

/**

 * @author anthakur

 *

 */

@Aspect

public class EmployeeAspect {

@After("execution(* com.bebo.dao.EmployeeDao.*(..))")

public void DisplayOnInsertEmployee(JoinPoint joinPoint){

System.out.println(" EmployeeDao method is invoked...."+joinPoint.getThis());

}

}

AppConfig.java

@EnableAspectJAutoProxy
@Configuration
@EnableAspectJAutoProxy
public class AppConfig {

@Bean
EmployeeAspect employeeAspect(){
return new EmployeeAspect();
}
}

Example: AspectEmployee.java

package com.bebo.aop;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class AspectEmployee {

    @Before("execution(* com.bebo.service.EmployeeService.*(..))")
    public void logServiceMethod(JoinPoint joinPoint){
        System.out.println("logServiceMethod loging the info for"+joinPoint.getSignature().getName());
       
    }
    @After("execution(* com.bebo.service.EmployeeService.*(..))")
    public void logServiceMethodAfterAfter(JoinPoint joinPoint){
        System.out.println("logServiceMethodAfterAfter loging the info for"+joinPoint.getSignature().getName());
       
    }
   
    @Around("execution(* com.bebo.service.EmployeeService.*(..))")
    public void logServiceMethodAfterAround(ProceedingJoinPoint joinPoint) throws Throwable{
        System.out.println("logServiceMethodAfterAround loging the info for"+joinPoint.getSignature().getName());
        joinPoint.proceed();
    }
   

    @AfterReturning("execution(* com.bebo.service.EmployeeService.*(..))")
    public void logServiceMethodAfterAfterReturning(JoinPoint joinPoint){
        System.out.println("logServiceMethodAfterAfterReturning loging the info for"+joinPoint.getSignature().getName());
       
    }
   
    @AfterThrowing("execution(* com.bebo.service.EmployeeService.*(..))")
    public void logServiceMethodAfterExpection(JoinPoint joinPoint){
        System.out.println("logServiceMethodAfterExpection loging the info for"+joinPoint.getSignature().getName());
       
    }

}