Spring AOP
- Aspect Oriented Programming
Concept
- Scattered duplicated code
- Caching, Logging, Transaction, Security, ...
- Devide Concerns
Terms
- JoinPoint
- Crosscutting Concerns 모듈이 삽입되어 동작할 수 있는 실행 가능한 특정 위치
- 메소드 호출, 메소드 실행 자체, 클래스 초기화, 객체 생성 시점 등
- Pointcut
- Pointcut은 어떤 클래스의 어느 JoinPoint를 사용할 것인지를 결정하는 선택 패턴
- 가장 일반적인 Pointcut은 ‘특정 클래스에 있는 모든 메소드 호출’로 구성
- 애스펙트(Aspect)
- Advice와 Pointcut의 조합
- 애플리케이션이 가지고 있어야 할 로직과 그것을 실행해야 하는 지점을 정의한 것
- Advice
- Advice는 관점(Aspect)의 실제 구현체로 결합점에 삽입되어 동작할 수 있는 코드
- Advice 는 결합점(JoinPoint)과 결합하여 동작하는 시점에 따라 before advice, after advice, around advice 타입으로 구분
- 특정 JoinPoint에 실행하는 코드
- Weaving
- Pointcut에 의해서 결정된 JoinPoint에 지정된 Advice를 삽입하는 과정
- Weaving은 AOP가 기존의 Core Concerns 모듈의 코드에 전혀 영향을 주지 않으면서 필요한 Crosscutting Concerns 기능을 추가할 수 있게 해 주는 핵심적인 처리 과정
Simple Example
Spring Boot
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
@Aspect
@Component
public class LoggingAspect {
private long startTime;
@Before("execution(* com.example..check*(..))")
public void onBeforeHandler(JoinPoint joinPoint) {
startTime = System.nanoTime();
System.out.println("start");
}
@After("execution(* com.example..check*(..))")
public void onAfterHandler(JoinPoint joinPoint) {
long endTime = System.nanoTime();
System.out.println("elapsed time: " + (endTime - startTime));
}
@Around("execution(* check*()) && within(com.example..*)")
public String around(ProceedingJoinPoint pjp) throws Throwable {
String returnValue = null;
try {
returnValue = (String) pjp.proceed();
} catch(Exception e) {
// log or re-throw the exception
}
// modify the return value
returnValue = "**" + returnValue + "**";
return returnValue;
}
}
@RestController
public class HotelController {
@GetMapping("/in")
@ResponseBody
public String checkIn() {
return "check-in";
}
@GetMapping("/out")
@ResponseBody
public String checkOut() {
return "check-in";
}
}
Spring Framework 3.x
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>3.2.18.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>3.2.18.RELEASE</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.9.5</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.9.5</version>
</dependency>
<?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="http://www.springframework.org/schema/beans
http://www.springframework.org/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/aop/spring-aop-3.2.xsd ">
<aop:config>
<aop:aspect id="log" ref="logging">
<aop:pointcut id="selectAll"
expression="execution(* com.okdevtv.spring.aop.*.*(..))" />
<aop:before pointcut-ref="selectAll" method="beforeAdvice" />
<aop:after pointcut-ref="selectAll" method="afterAdvice" />
<aop:after-returning pointcut-ref="selectAll"
returning="retVal" method="afterReturningAdvice" />
<aop:after-throwing pointcut-ref="selectAll"
throwing="ex" method="AfterThrowingAdvice" />
</aop:aspect>
</aop:config>
<!-- Definition for student bean -->
<bean id="student" class="com.okdevtv.spring.aop.Student">
<property name="name" value="Zara" />
<property name="age" value="11" />
</bean>
<!-- Definition for logging aspect -->
<bean id="logging" class="com.okdevtv.spring.aop.Logging" />
</beans>
package com.okdevtv.spring.aop;
public class Student {
private Integer age;
private String name;
public void setAge(Integer age) {
this.age = age;
}
public Integer getAge() {
System.out.println("Age : " + age);
return age;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
System.out.println("Name : " + name);
return name;
}
public void printThrowException() {
System.out.println("Exception raised");
throw new IllegalArgumentException();
}
}
package com.okdevtv.spring.aop;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
Student student = (Student) context.getBean("student");
student.getName();
student.getAge();
student.printThrowException();
}
}
package com.okdevtv.spring.aop;
public class Logging {
/**
* This is the method which I would like to execute before a selected method
* execution.
*/
public void beforeAdvice() {
System.out.println("Going to setup student profile.");
}
/**
* This is the method which I would like to execute after a selected method
* execution.
*/
public void afterAdvice() {
System.out.println("Student profile has been setup.");
}
/**
* This is the method which I would like to execute when any method returns.
*/
public void afterReturningAdvice(Object retVal) {
System.out.println("Returning:" + retVal.toString());
}
/**
* This is the method which I would like to execute if there is an exception
* raised.
*/
public void AfterThrowingAdvice(IllegalArgumentException ex) {
System.out.println("There has been an exception: " + ex.toString());
}
}
<aop:config>
<aop:aspect id="log" ref="logging">
<aop:pointcut id="selectAll"
expression="execution(* com.okdevtv.spring.aop.Student.getName(..))" />
<aop:before pointcut-ref="selectAll" method="beforeAdvice" />
<aop:after pointcut-ref="selectAll" method="afterAdvice" />
</aop:aspect>
</aop:config>
ref
OKdevTV
