Introductions（引用），在 Aspect 中称为类型间的声明，使切面能够声明被通知的对象（拦截的对象）实现给定的接口，并提供该接口的实现。
简单点说可以将一个类的实现方法复制到未实现的类中，动态的扩展类没有的方法。
通过 @DeclareParents 注解进行声明，声明在一个父类型的属性上（比如接口），其中注解的属性 value 指定对哪些路径（包）下的类进行类方法扩展，defaultImpl 指定以哪个类为模板。
如下案例：
1）切面类：
@Aspect @Component public class LogAspects { @DeclareParents(value = "com.hrh.aop.*", defaultImpl = IndexDao.class) public static Dao dao; @Pointcut("execution(public * com.hrh.aop.*.*(..))") public void pointcut() { } @Before("pointcut()") public void LogStart() { System.out.println("LogStart..."); } }
2）接口和实现类：
public interface Dao{ void query(); } @Repository public class IndexDao implements Dao{ public void query(){ System.out.println("query："+this.getClass().getSimpleName()); } }
3）配置类：
@Configuration @EnableAspectJAutoProxy @ComponentScan("com.hrh.aop") public class Config { }
4）空类：
@Repository("orderDao")
public class OrderDao{}
5）测试和结果：
public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Config.class); Dao bean = (Dao) context.getBean("indexDao"); bean.query(); System.out.println("----------"); Dao dao = (Dao) context.getBean("orderDao"); dao.query(); } =========结果========== LogStart... query：IndexDao ---------- query：IndexDao
根据前文Spring笔记(3) - SpringAOP基础详解和源码探究可以得知如下：
- @EnableAspectJAutoProxy(proxyTargetClass=false)，表示使用JDK动态代理（默认）；
- @EnableAspectJAutoProxy(proxyTargetClass=true)，表示使用CGLIB代理；
debug运行后查看beanFactory的OrderDao和IndexDao代理后的对象，如下图：
从上面可以看到IndexDao的对象是使用JDK代理的，而OrderDao的对象是CGLIB代理的。
那么当设置@EnableAspectJAutoProxy(proxyTargetClass=true)时，是如下图：
由此可以判定@DeclareParents注解给拦截到的类进行代理使用的是CGLIB代理（其实OrderDao没有实现任何接口，所以最终实现的是CGLIB），那么可以查看下代理类生成的内容是什么，可以在context前面加一行代码将代理类class文件存入本地磁盘：
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "xxx");//xxx是存放代理类class的本地路径 AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(Config.class);
下面是代理类class反编译后的完整代码（感兴趣可以完全打开，完全的很多内容，包含了各种父类的方法，比如toString、clone、equals、hashCode）：
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package com.hrh.aop; import java.lang.reflect.Method; import java.lang.reflect.UndeclaredThrowableException; import org.aopalliance.aop.Advice; import org.springframework.aop.Advisor; import org.springframework.aop.SpringProxy; import org.springframework.aop.TargetClassAware; import org.springframework.aop.TargetSource; import org.springframework.aop.framework.Advised; import org.springframework.aop.framework.AopConfigException; import org.springframework.cglib.core.ReflectUtils; import org.springframework.cglib.core.Signature; import org.springframework.cglib.proxy.Callback; import org.springframework.cglib.proxy.Dispatcher; import org.springframework.cglib.proxy.Factory; import org.springframework.cglib.proxy.MethodInterceptor; import org.springframework.cglib.proxy.MethodProxy; import org.springframework.cglib.proxy.NoOp; public class OrderDao$$EnhancerBySpringCGLIB$$ee33136 extends OrderDao implements Dao, SpringProxy, Advised, Factory { private boolean CGLIB$BOUND; public static Object CGLIB$FACTORY_DATA; private static final ThreadLocal CGLIB$THREAD_CALLBACKS; private static final Callback[] CGLIB$STATIC_CALLBACKS; private MethodInterceptor CGLIB$CALLBACK_0; private MethodInterceptor CGLIB$CALLBACK_1; private NoOp CGLIB$CALLBACK_2; private Dispatcher CGLIB$CALLBACK_3; private Dispatcher CGLIB$CALLBACK_4; private MethodInterceptor CGLIB$CALLBACK_5; private MethodInterceptor CGLIB$CALLBACK_6; private static Object CGLIB$CALLBACK_FILTER; private static final Method CGLIB$equals$0$Method; private static final MethodProxy CGLIB$equals$0$Proxy; private static final Object[] CGLIB$emptyArgs; private static final Method CGLIB$toString$1$Method; private static final MethodProxy CGLIB$toString$1$Proxy; private static final Method CGLIB$hashCode$2$Method; private static final MethodProxy CGLIB$hashCode$2$Proxy; private static final Method CGLIB$clone$3$Method; private static final MethodProxy CGLIB$clone$3$Proxy; private static final Method CGLIB$query$4$Method; private static final MethodProxy CGLIB$query$4$Proxy; static void CGLIB$STATICHOOK5() { CGLIB$THREAD_CALLBACKS = new ThreadLocal(); CGLIB$emptyArgs = new Object[0]; Class var0 = Class.forName("com.hrh.aop.OrderDao$$EnhancerBySpringCGLIB$$ee33136"); Class var1; Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods()); CGLIB$equals$0$Method = var10000[0]; CGLIB$equals$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$0"); CGLIB$toString$1$Method = var10000[1]; CGLIB$toString$1$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$1"); CGLIB$hashCode$2$Method = var10000[2]; CGLIB$hashCode$2$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$2"); CGLIB$clone$3$Method = var10000[3]; CGLIB$clone$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$3"); CGLIB$query$4$Method = ReflectUtils.findMethods(new String[]{"query", "()V"}, (var1 = Class.forName("com.hrh.aop.Dao")).getDeclaredMethods())[0]; CGLIB$query$4$Proxy = MethodProxy.create(var1, var0, "()V", "query", "CGLIB$query$4"); } final boolean CGLIB$equals$0(Object var1) { return super.equals(var1); } public final boolean equals(Object var1) { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_5; if (this.CGLIB$CALLBACK_5 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_5; } if (var10000 != null) { Object var4 = var10000.intercept(this, CGLIB$equals$0$Method, new Object[]{var1}, CGLIB$equals$0$Proxy); return var4 == null ? false : (Boolean)var4; } else { return super.equals(var1); } } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } final String CGLIB$toString$1() { return super.toString(); } public final String toString() { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$1$Method, CGLIB$emptyArgs, CGLIB$toString$1$Proxy) : super.toString(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } final int CGLIB$hashCode$2() { return super.hashCode(); } public final int hashCode() { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_6; if (this.CGLIB$CALLBACK_6 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_6; } if (var10000 != null) { Object var3 = var10000.intercept(this, CGLIB$hashCode$2$Method, CGLIB$emptyArgs, CGLIB$hashCode$2$Proxy); return var3 == null ? 0 : ((Number)var3).intValue(); } else { return super.hashCode(); } } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } final Object CGLIB$clone$3() throws CloneNotSupportedException { return super.clone(); } protected final Object clone() throws CloneNotSupportedException { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } return var10000 != null ? var10000.intercept(this, CGLIB$clone$3$Method, CGLIB$emptyArgs, CGLIB$clone$3$Proxy) : super.clone(); } catch (Error | CloneNotSupportedException | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } final void CGLIB$query$4() { super.query(); } public final void query() { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { var10000.intercept(this, CGLIB$query$4$Method, CGLIB$emptyArgs, CGLIB$query$4$Proxy); } else { super.query(); } } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public static MethodProxy CGLIB$findMethodProxy(Signature var0) { String var10000 = var0.toString(); switch(var10000.hashCode()) { case -1166709331: if (var10000.equals("query()V")) { return CGLIB$query$4$Proxy; } break; case -508378822: if (var10000.equals("clone()Ljava/lang/Object;")) { return CGLIB$clone$3$Proxy; } break; case 1826985398: if (var10000.equals("equals(Ljava/lang/Object;)Z")) { return CGLIB$equals$0$Proxy; } break; case 1913648695: if (var10000.equals("toString()Ljava/lang/String;")) { return CGLIB$toString$1$Proxy; } break; case 1984935277: if (var10000.equals("hashCode()I")) { return CGLIB$hashCode$2$Proxy; } } return null; } public final int indexOf(Advice var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).indexOf(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final int indexOf(Advisor var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).indexOf(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final boolean isFrozen() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).isFrozen(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final void setTargetSource(TargetSource var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).setTargetSource(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final Advisor[] getAdvisors() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).getAdvisors(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final boolean isProxyTargetClass() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).isProxyTargetClass(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final void addAdvice(Advice var1) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).addAdvice(var1); } catch (Error | AopConfigException | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final void addAdvice(int var1, Advice var2) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).addAdvice(var1, var2); } catch (Error | AopConfigException | RuntimeException var3) { throw var3; } catch (Throwable var4) { throw new UndeclaredThrowableException(var4); } } public final boolean replaceAdvisor(Advisor var1, Advisor var2) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).replaceAdvisor(var1, var2); } catch (Error | AopConfigException | RuntimeException var3) { throw var3; } catch (Throwable var4) { throw new UndeclaredThrowableException(var4); } } public final void addAdvisor(int var1, Advisor var2) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).addAdvisor(var1, var2); } catch (Error | AopConfigException | RuntimeException var3) { throw var3; } catch (Throwable var4) { throw new UndeclaredThrowableException(var4); } } public final void addAdvisor(Advisor var1) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).addAdvisor(var1); } catch (Error | AopConfigException | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final boolean isPreFiltered() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).isPreFiltered(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final boolean removeAdvice(Advice var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).removeAdvice(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final void removeAdvisor(int var1) throws AopConfigException { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).removeAdvisor(var1); } catch (Error | AopConfigException | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final boolean removeAdvisor(Advisor var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).removeAdvisor(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final TargetSource getTargetSource() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).getTargetSource(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final void setPreFiltered(boolean var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).setPreFiltered(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final boolean isExposeProxy() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).isExposeProxy(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final void setExposeProxy(boolean var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } ((Advised)var10000.loadObject()).setExposeProxy(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final Class[] getProxiedInterfaces() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).getProxiedInterfaces(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final boolean isInterfaceProxied(Class var1) { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).isInterfaceProxied(var1); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public final String toProxyConfigString() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((Advised)var10000.loadObject()).toProxyConfigString(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public final Class getTargetClass() { try { Dispatcher var10000 = this.CGLIB$CALLBACK_4; if (this.CGLIB$CALLBACK_4 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_4; } return ((TargetClassAware)var10000.loadObject()).getTargetClass(); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public OrderDao$$EnhancerBySpringCGLIB$$ee33136() { try { super(); CGLIB$BIND_CALLBACKS(this); } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) { CGLIB$THREAD_CALLBACKS.set(var0); } public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) { CGLIB$STATIC_CALLBACKS = var0; } private static final void CGLIB$BIND_CALLBACKS(Object var0) { OrderDao$$EnhancerBySpringCGLIB$$ee33136 var1 = (OrderDao$$EnhancerBySpringCGLIB$$ee33136)var0; if (!var1.CGLIB$BOUND) { var1.CGLIB$BOUND = true; Object var10000 = CGLIB$THREAD_CALLBACKS.get(); if (var10000 == null) { var10000 = CGLIB$STATIC_CALLBACKS; if (CGLIB$STATIC_CALLBACKS == null) { return; } } Callback[] var10001 = (Callback[])var10000; var1.CGLIB$CALLBACK_6 = (MethodInterceptor)((Callback[])var10000)[6]; var1.CGLIB$CALLBACK_5 = (MethodInterceptor)var10001[5]; var1.CGLIB$CALLBACK_4 = (Dispatcher)var10001[4]; var1.CGLIB$CALLBACK_3 = (Dispatcher)var10001[3]; var1.CGLIB$CALLBACK_2 = (NoOp)var10001[2]; var1.CGLIB$CALLBACK_1 = (MethodInterceptor)var10001[1]; var1.CGLIB$CALLBACK_0 = (MethodInterceptor)var10001[0]; } } public Object newInstance(Callback[] var1) { try { CGLIB$SET_THREAD_CALLBACKS(var1); OrderDao$$EnhancerBySpringCGLIB$$ee33136 var10000 = new OrderDao$$EnhancerBySpringCGLIB$$ee33136(); CGLIB$SET_THREAD_CALLBACKS((Callback[])null); return var10000; } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public Object newInstance(Callback var1) { try { throw new IllegalStateException("More than one callback object required"); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) { try { CGLIB$SET_THREAD_CALLBACKS(var3); OrderDao$$EnhancerBySpringCGLIB$$ee33136 var10000 = new OrderDao$$EnhancerBySpringCGLIB$$ee33136; switch(var1.length) { case 0: var10000.<init>(); CGLIB$SET_THREAD_CALLBACKS((Callback[])null); return var10000; default: throw new IllegalArgumentException("Constructor not found"); } } catch (Error | RuntimeException var4) { throw var4; } catch (Throwable var5) { throw new UndeclaredThrowableException(var5); } } public Callback getCallback(int var1) { try { CGLIB$BIND_CALLBACKS(this); Object var10000; switch(var1) { case 0: var10000 = this.CGLIB$CALLBACK_0; break; case 1: var10000 = this.CGLIB$CALLBACK_1; break; case 2: var10000 = this.CGLIB$CALLBACK_2; break; case 3: var10000 = this.CGLIB$CALLBACK_3; break; case 4: var10000 = this.CGLIB$CALLBACK_4; break; case 5: var10000 = this.CGLIB$CALLBACK_5; break; case 6: var10000 = this.CGLIB$CALLBACK_6; break; default: var10000 = null; } return (Callback)var10000; } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } public void setCallback(int var1, Callback var2) { try { switch(var1) { case 0: this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2; break; case 1: this.CGLIB$CALLBACK_1 = (MethodInterceptor)var2; break; case 2: this.CGLIB$CALLBACK_2 = (NoOp)var2; break; case 3: this.CGLIB$CALLBACK_3 = (Dispatcher)var2; break; case 4: this.CGLIB$CALLBACK_4 = (Dispatcher)var2; break; case 5: this.CGLIB$CALLBACK_5 = (MethodInterceptor)var2; break; case 6: this.CGLIB$CALLBACK_6 = (MethodInterceptor)var2; } } catch (Error | RuntimeException var3) { throw var3; } catch (Throwable var4) { throw new UndeclaredThrowableException(var4); } } public Callback[] getCallbacks() { try { CGLIB$BIND_CALLBACKS(this); return new Callback[]{this.CGLIB$CALLBACK_0, this.CGLIB$CALLBACK_1, this.CGLIB$CALLBACK_2, this.CGLIB$CALLBACK_3, this.CGLIB$CALLBACK_4, this.CGLIB$CALLBACK_5, this.CGLIB$CALLBACK_6}; } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } public void setCallbacks(Callback[] var1) { try { this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0]; this.CGLIB$CALLBACK_1 = (MethodInterceptor)var1[1]; this.CGLIB$CALLBACK_2 = (NoOp)var1[2]; this.CGLIB$CALLBACK_3 = (Dispatcher)var1[3]; this.CGLIB$CALLBACK_4 = (Dispatcher)var1[4]; this.CGLIB$CALLBACK_5 = (MethodInterceptor)var1[5]; this.CGLIB$CALLBACK_6 = (MethodInterceptor)var1[6]; } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } static { CGLIB$STATICHOOK6(); CGLIB$STATICHOOK5(); } static void CGLIB$STATICHOOK6() { try { ; } catch (Error | RuntimeException var0) { throw var0; } catch (Throwable var1) { throw new UndeclaredThrowableException(var1); } } }
从上面可以看到代理类里面有query方法，代理类继承了OrderDao和实现了Dao接口：
public class OrderDao$$EnhancerBySpringCGLIB$$ee33136 extends OrderDao implements Dao, SpringProxy, Advised, Factory { ............................ final void CGLIB$query$4() { super.query(); } public final void query() { try { MethodInterceptor var10000 = this.CGLIB$CALLBACK_0; if (this.CGLIB$CALLBACK_0 == null) { CGLIB$BIND_CALLBACKS(this); var10000 = this.CGLIB$CALLBACK_0; } if (var10000 != null) { var10000.intercept(this, CGLIB$query$4$Method, CGLIB$emptyArgs, CGLIB$query$4$Proxy); } else { super.query(); } } catch (Error | RuntimeException var1) { throw var1; } catch (Throwable var2) { throw new UndeclaredThrowableException(var2); } } ............................ }
从前文Spring笔记(3) - SpringAOP基础详解和源码探究可以得知在 AbstractAutoProxyCreator#wrapIfNecessary()中会对bean进行包装增强（代理），下面打下断点debug跟踪下流程：
当执行到wrapIfNecessary方法下面的代码时，bean还是原对象（未被代理）：
Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
当上面的代码执行完后，可以看到specificInterceptors数组包含了advice(通知)、introducedInterface(引用接口）、typePatternClassFilter(class过滤规则，重点)，其中advice包含了defaultImplType(默认实现类型，上面代码中定义的），可以看到是IndexDao，interfaceType(接口类型)可以看到是Dao，以上信息是通过解析@DeclareParents注解而来的：
下面typePatternClassFilter里面的详情，可以看到，上面的信息又包含在typePatternClassFilter里面，同时里面包含了过滤规则：
最后通过DefaultAopProxyFactory#createAopProxy方法创建的对象如下图：
当执行query方法时，CglibAopProxy.DynamicAdvisedInterceptor#intercept方法进行拦截时，会执行父类的方法ReflectiveMethodInvocation#ReflectiveMethodInvocation：
执行完会跳转到ReflectiveMethodInvocation#proceed执行方法的执行：
public Object proceed() throws Throwable { // We start with an index of -1 and increment early. if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) { return invokeJoinpoint(); } //获取通知 Object interceptorOrInterceptionAdvice = this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex); if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) { // Evaluate dynamic method matcher here: static part will already have // been evaluated and found to match. InterceptorAndDynamicMethodMatcher dm = (InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice; if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) { return dm.interceptor.invoke(this); } else { // Dynamic matching failed. // Skip this interceptor and invoke the next in the chain. return proceed(); } } else { // It's an interceptor, so we just invoke it: The pointcut will have // been evaluated statically before this object was constructed. return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);//执行方法 } }
下面执行delegate对象获取到IndexDao，然后AopUtils.invokeJoinpointUsingReflection执行IndexDao的query实现方法：
其中getIntroductionDelegateFor方法中的delegate通过反射对默认实现类型进行构造方法实例化后调用实例化的方法，由此可以看出上面的第二次打印结果没有打印前置通知的内容，因为此时IndexoDao的对象是原对象，不是代理对象：
总结：Introductions（引用）通过 @DeclareParents 注解实现，可以给一个空白类进行方法复制，它通过解析@DeclareParents 注解信息，代理时将定义的静态接口变量作为它的父类，并实现它的方法，方法执行时调用的是defaultImpl 指定的类模板的实现方法；
参考：https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#aop-introductions