Spring CglibSubclassingInstantiationStrategy

public Object instantiate(@Nullable Constructor<?> ctor, Object... args) {
   // 创造 CGLIB 对原有 BeanClass 的增强类
   Class<?> subclass = createEnhancedSubclass(this.beanDefinition);
   Object instance;
   if (ctor == null) {
      // 构造函数为空的情况下创建
      instance = BeanUtils.instantiateClass(subclass);
   }
   else {
      try {
         // 从 subClass 中查询对应的 构造函数
         Constructor<?> enhancedSubclassConstructor = subclass.getConstructor(ctor.getParameterTypes());
         // 创建对象
         instance = enhancedSubclassConstructor.newInstance(args);
      }
      catch (Exception ex) {
         throw new BeanInstantiationException(this.beanDefinition.getBeanClass(),
               "Failed to invoke constructor for CGLIB enhanced subclass [" + subclass.getName() + "]", ex);
      }
   }
   // SPR-10785: set callbacks directly on the instance instead of in the
   // enhanced class (via the Enhancer) in order to avoid memory leaks.
   Factory factory = (Factory) instance;

   // 设置 Factory 的回调
   factory.setCallbacks(new Callback[] { NoOp.INSTANCE,
         new LookupOverrideMethodInterceptor(this.beanDefinition, this.owner),
         new ReplaceOverrideMethodInterceptor(this.beanDefinition, this.owner) });
   return instance;
}

/**
 * Create an enhanced subclass of the bean class for the provided bean
 * definition, using CGLIB.
 * 创造出 CGLIB 对 BeanClass 的增强子类
 */
private Class<?> createEnhancedSubclass(RootBeanDefinition beanDefinition) {
   Enhancer enhancer = new Enhancer();
   enhancer.setSuperclass(beanDefinition.getBeanClass());
   enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
   if (this.owner instanceof ConfigurableBeanFactory) {
      ClassLoader cl = ((ConfigurableBeanFactory) this.owner).getBeanClassLoader();
      enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(cl));
   }
   enhancer.setCallbackFilter(new MethodOverrideCallbackFilter(beanDefinition));
   enhancer.setCallbackTypes(CALLBACK_TYPES);
   return enhancer.createClass();
}

private static class CglibIdentitySupport {

   private final RootBeanDefinition beanDefinition;

   public CglibIdentitySupport(RootBeanDefinition beanDefinition) {
      this.beanDefinition = beanDefinition;
   }

   public RootBeanDefinition getBeanDefinition() {
      return this.beanDefinition;
   }

   @Override
   public boolean equals(@Nullable Object other) {
      return (other != null && getClass() == other.getClass() &&
            this.beanDefinition.equals(((CglibIdentitySupport) other).beanDefinition));
   }

   @Override
   public int hashCode() {
      return this.beanDefinition.hashCode();
   }
}

if (methodOverride == null) {
   return PASSTHROUGH;
}
else if (methodOverride instanceof LookupOverride) {
   return LOOKUP_OVERRIDE;
}
else if (methodOverride instanceof ReplaceOverride) {
   return METHOD_REPLACER;
}

@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy mp) throws Throwable {
   // Cast is safe, as CallbackFilter filters are used selectively.
   LookupOverride lo = (LookupOverride) getBeanDefinition().getMethodOverrides().getOverride(method);
   Assert.state(lo != null, "LookupOverride not found");
   Object[] argsToUse = (args.length > 0 ? args : null);  // if no-arg, don't insist on args at all
   if (StringUtils.hasText(lo.getBeanName())) {
      return (argsToUse != null ? this.owner.getBean(lo.getBeanName(), argsToUse) :
            this.owner.getBean(lo.getBeanName()));
   }
   else {
      return (argsToUse != null ? this.owner.getBean(method.getReturnType(), argsToUse) :
            this.owner.getBean(method.getReturnType()));
   }
}