15. 스프링 AOP 기능

public class LoggingAdvice
        implements MethodBeforeAdvice {

    @Override
    public void before(
            Method method,    // 실행된 메서드
            Object[] args,    // 메서드 인자
            Object target     // 대상 객체
    ) throws Throwable {
        System.out.println(
            "[LOG] " + method.getName() + " 호출"
        );
    }
}

public class AfterLogAdvice
        implements AfterReturningAdvice {

    @Override
    public void afterReturning(
            Object returnValue, // 반환값
            Method method,      // 실행된 메서드
            Object[] args,      // 메서드 인자
            Object target       // 대상 객체
    ) throws Throwable {
        System.out.println(
            "[LOG] " + method.getName() + " 완료"
        );
    }
}

public class ExceptionAdvice
        implements ThrowsAdvice {

    public void afterThrowing(
            Method method,     // 실행된 메서드
            Object[] args,     // 메서드 인자
            Object target,     // 대상 객체
            Exception ex       // 발생한 예외
    ) {
        System.out.println(
            "[예외] " + ex.getMessage()
        );
    }
}

public class AroundAdvice
        implements MethodInterceptor {

    @Override
    public Object invoke(
            MethodInvocation invocation)
            throws Throwable {

        // ── before ──
        System.out.println("[전처리] 시작");

        Object result;
        try {
            // 주기능 실행
            result = invocation.proceed();
        } catch (Exception e) {
            // ── throws ──
            System.out.println("[예외] " + e);
            throw e;
        }

        // ── after ──
        System.out.println("[후처리] 완료");
        return result;
    }
}

// 인터페이스
public interface Calculator {
    int add(int a, int b);
    int sub(int a, int b);
}

// 구현체 (Target)
public class CalculatorImpl
        implements Calculator {

    @Override
    public int add(int a, int b) {
        return a + b;
    }

    @Override
    public int sub(int a, int b) {
        return a - b;
    }
}

<beans ...>
    <!-- 1. Target 빈 -->
    <bean id="calcTarget"
        class="com.aop.CalculatorImpl" />

    <!-- 2. Advice 빈 -->
    <bean id="loggingAdvice"
        class="com.aop.LoggingAdvice" />

    <!-- 3. Pointcut 설정 (정규식) -->
    <bean id="calcPointcut"
      class="org.springframework.aop.support
             .JdkRegexpMethodPointcut">
        <property name="pattern"
            value=".*add.*" />
    </bean>

    <!-- 4. Advisor = Advice + Pointcut -->
    <bean id="calcAdvisor"
      class="org.springframework.aop.support
             .DefaultPointcutAdvisor">
        <property name="pointcut"
            ref="calcPointcut" />
        <property name="advice"
            ref="loggingAdvice" />
    </bean>

    <!-- 5. ProxyFactoryBean -->
    <bean id="calculator"
      class="org.springframework.aop.framework
             .ProxyFactoryBean">
        <property name="target"
            ref="calcTarget" />
        <property name="interceptorNames">
            <list>
                <value>calcAdvisor</value>
            </list>
        </property>
    </bean>
</beans>

ApplicationContext ctx =
    new ClassPathXmlApplicationContext(
        "aop.xml"
    );

Calculator calc =
    (Calculator) ctx.getBean("calculator");

// add → Pointcut 매칭 → Advice 실행
calc.add(10, 20);
// [LOG] add 호출
// 30

// sub → Pointcut 미매칭 → Advice 미실행
calc.sub(20, 5);
// 15