spring core aop : proxy - type casting problem

spring-core/aop/src/test/java/com/example/aop/proxyvs/ProxyCastingTest.java

@@ -0,0 +1,42 @@
+package com.example.aop.proxyvs;
+
+import com.example.aop.member.MemberService;
+import com.example.aop.member.MemberServiceImpl;
+import lombok.extern.slf4j.Slf4j;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.springframework.aop.framework.ProxyFactory;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@Slf4j
+public class ProxyCastingTest {
+
+    @Test
+    void jdkProxy() {
+        MemberServiceImpl target = new MemberServiceImpl();
+        ProxyFactory proxyFactory = new ProxyFactory(target);
+        proxyFactory.setProxyTargetClass(false); // JDK 동적 프록시 (인터페이스 기반)
+
+        // 프록시를 인터페이스로 캐스팅 가능
+        MemberService memberServiceProxy = (MemberService) proxyFactory.getProxy();
+
+        // JDK 동적 프록시를 구현 클래스로 캐스팅 불가능, ClassCastException 예외 발생
+        assertThrows(ClassCastException.class, () -> {
+            MemberServiceImpl casingMemberService = (MemberServiceImpl) memberServiceProxy;
+        });
+    }
+
+    @Test
+    void cglibProxy() {
+        MemberServiceImpl target = new MemberServiceImpl();
+        ProxyFactory proxyFactory = new ProxyFactory(target);
+        proxyFactory.setProxyTargetClass(true); // CGLIB 프록시 (구현체 기반)
+
+        // 프록시를 인터페이스로 캐스팅 가능
+        MemberService memberServiceProxy = (MemberService) proxyFactory.getProxy();
+
+        // CGLIB 프록시를 구현 클래스로 캐스팅 가능
+        MemberServiceImpl casingMemberService = (MemberServiceImpl) memberServiceProxy;
+    }
+}

spring-core/aop/src/test/java/com/example/aop/proxyvs/ProxyDITest.java

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+package com.example.aop.proxyvs;
+
+import com.example.aop.member.MemberService;
+import com.example.aop.member.MemberServiceImpl;
+import com.example.aop.proxyvs.code.ProxyDIAspect;
+import lombok.extern.slf4j.Slf4j;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Import;
+
+@Slf4j
+//@SpringBootTest(properties = {"spring.aop.proxy-target-class=false"}) // JDK 동적 프록시
+//@SpringBootTest(properties = {"spring.aop.proxy-target-class=true"}) // CGLIB 프록시
+@SpringBootTest
+@Import(ProxyDIAspect.class)
+public class ProxyDITest {
+
+    @Autowired
+    MemberService memberService;
+
+    /**
+     * JDK 동적 프록시 생성 시 타입 캐스트 불가능 (인터페이스 기반이므로 구체클래스를 알 수 없다.)
+     */
+    @Autowired
+    MemberServiceImpl memberServiceImpl;
+
+    @Test
+    void go() {
+        log.info("memberService class={}", memberService.getClass());
+        log.info("memberServiceImpl class={}", memberServiceImpl.getClass());
+        memberService.hello("hello");
+    }
+}

spring-core/aop/src/test/java/com/example/aop/proxyvs/code/ProxyDIAspect.java

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+package com.example.aop.proxyvs.code;
+
+import lombok.extern.slf4j.Slf4j;
+import org.aspectj.lang.JoinPoint;
+import org.aspectj.lang.annotation.Aspect;
+import org.aspectj.lang.annotation.Before;
+
+@Slf4j
+@Aspect
+public class ProxyDIAspect {
+
+    @Before("execution(* com.example.aop..*.*(..))")
+    public void doTrace(JoinPoint joinPoint) {
+        log.info("[proxyDIAdvice] {}", joinPoint.getSignature());
+    }
+}