CGLIB 프록시 제약 사항 테스트.
@Component
public class FinalHello implements Hello {
public class FinalHello implements Hello {
public String hi() {
return "hi";
}
public final void finalHi(){
System.out.println("안녕");
}
}
위 클래스에 모든 메소드 호출을 포인트컷으로 간단한 Adivce를 적용하여 CGLIB 프록시를 생성했을 때, 다음과 같은 결과를 확인할 수 있었습니다.
1. final 메소드를 호출할 경우 Advice를 적용하지 않음.
2. final이 아닌 메소드에는 Advice가 적용됨.
이런 간단한 테스트를 해보기 전에는 막연히 final 메소드가 있으면 CGLIB 프록시를 못 만드는 건가 싶었는데, 그게 아니었습니다.
한 가지 더 확인해봤습니다. 기본 생성자(인자가 없는 생성자)가 반드시 있어야 한다고 본것 같아서, 그걸 확인해봤습니다. 위의 경우에는 기본 생성자가 있는 상태로 테스트를 했으니까 기본 생성자 없이 테스트를 한 번 더 해보면 되겠죠.
@Component
public class FinalHello implements Hello {
String hi;
public FinalHello(String hi) {
this.hi = hi;
}
public class FinalHello implements Hello {
String hi;
public FinalHello(String hi) {
this.hi = hi;
}
public String hi() {
return hi;
}
public final void finalHi(){
System.out.println("안녕");
}
}
그리고 위에서 실행했던 테스트 코드와 애스팩트를 그대로 사용해봤습니다.
java.lang.IllegalStateException: Failed to load ApplicationContext
at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:203)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:109)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:255)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:93)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.invokeTestMethod(SpringJUnit4ClassRunner.java:130)
at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51)
at org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:44)
at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27)
at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37)
at org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:42)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'finalHello' defined in file [C:\workspace\osaf\target\test-classes\org\opensprout\sandbox\proxy\withfinal\FinalHello.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.opensprout.sandbox.proxy.withfinal.FinalHello]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:883)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:839)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:221)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:84)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:42)
at org.springframework.test.context.TestContext.loadApplicationContext(TestContext.java:173)
at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:199)
... 16 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.opensprout.sandbox.proxy.withfinal.FinalHello]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:58)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:877)
... 33 more
Caused by: java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at java.lang.Class.getConstructor0(Class.java:2706)
at java.lang.Class.getDeclaredConstructor(Class.java:1985)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:54)
... 34 more
at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:203)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:109)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:255)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:93)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.invokeTestMethod(SpringJUnit4ClassRunner.java:130)
at org.junit.internal.runners.JUnit4ClassRunner.runMethods(JUnit4ClassRunner.java:51)
at org.junit.internal.runners.JUnit4ClassRunner$1.run(JUnit4ClassRunner.java:44)
at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:27)
at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:37)
at org.junit.internal.runners.JUnit4ClassRunner.run(JUnit4ClassRunner.java:42)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'finalHello' defined in file [C:\workspace\osaf\target\test-classes\org\opensprout\sandbox\proxy\withfinal\FinalHello.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.opensprout.sandbox.proxy.withfinal.FinalHello]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:883)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:839)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
at java.security.AccessController.doPrivileged(Native Method)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:221)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:729)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:381)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:84)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:42)
at org.springframework.test.context.TestContext.loadApplicationContext(TestContext.java:173)
at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:199)
... 16 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.opensprout.sandbox.proxy.withfinal.FinalHello]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:58)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:877)
... 33 more
Caused by: java.lang.NoSuchMethodException: org.opensprout.sandbox.proxy.withfinal.FinalHello.<init>()
at java.lang.Class.getConstructor0(Class.java:2706)
at java.lang.Class.getDeclaredConstructor(Class.java:1985)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:54)
... 34 more
맞네요. 두 번쨰 제약 사항까지 살펴봤습니다.
CGLIB 프록시가 JDK 프록시에 비해 성능도 좋고, concrete 클래스의 프록시도 만들어 주기 때문에, 좋긴 한데, 위의 두 개의 제약 사항(final 메소드에는 어드바이스 적용 불가(상속을 못하니까.), 기본 생성자 필요.)에 주의 하면서 사용해야겠습니다.
만약에 이런 경우엔 어떻게 해야 할까요.
1. 구현하는 인터페이스 없음 ==> JDK 프록시 사용불가
2. 기본 생성자 없음 ==> CGLIB 사용불가
3. 어드바이스 적용하고자 하는 메소드가 fianl ==> 역시 CGLIB 사용불가
4. 하지만 AOP 하고파. ==> Spring AOP로는 불가능.
결론(지금은 머리로만 생각한 겁니다. 검증은 조금 뒤에..)
==> Spring AOP + AspectJ 연동해서, 빌드 타임에 aspectj-waever를 사용하던가, 클래스 로딩 타임에 loadtime-weaving을 하면 될 것입니다. AspectJ를 사용한 위빙은 프록시를 만드는게 아니라, 바이트코드랑 .aj 파일을 조작해서 타겟 클래스에 대한 .class파일을 다시 생성하고 그 코드를 사용하는 것이기 때문에 런타임시에 부하도 없고 위와 같은 Spring AOP 제약에서 벗어날 수 있으리라 봅니다.