从@Async案例找到Spring框架的bug：exposeProxy=true不生效原因大剖析+最佳解决方案【享学Spring】(中)

@Service
public class B implements BInterface {
  ...
    @Async
    public void fun2(){
        System.out.println("线程名称：" + Thread.currentThread().getName());
    }
}

BInterface bInterface = applicationContext.getBean(BInterface.class); // 正常获取到容器里的代理对象
applicationContext.getBean(B.class); //报错  NoSuchBeanDefinitionException
// 原因此处不再解释了，若是CGLIB代理，两种获取方式均可~

// @since 13.03.2003
public final class AopContext {
  private static final ThreadLocal<Object> currentProxy = new NamedThreadLocal<>("Current AOP proxy");
  private AopContext() {
  }
  // 该方法是public static方法，说明可以被任意类进行调用
  public static Object currentProxy() throws IllegalStateException {
    Object proxy = currentProxy.get();
    // 它抛出异常的原因是当前线程并没有绑定对象
    // 而给线程版定对象的方法在下面：特别有意思的是它的访问权限是default级别，也就是说只能Spring内部去调用~
    if (proxy == null) {
      throw new IllegalStateException("Cannot find current proxy: Set 'exposeProxy' property on Advised to 'true' to make it available.");
    }
    return proxy;
  }
  // 它最有意思的地方是它的访问权限是default的，表示只能给Spring内部去调用~
  // 调用它的类有CglibAopProxy和JdkDynamicAopProxy
  @Nullable
  static Object setCurrentProxy(@Nullable Object proxy) {
    Object old = currentProxy.get();
    if (proxy != null) {
      currentProxy.set(proxy);
    } else {
      currentProxy.remove();
    }
    return old;
  }
}

final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {
  ...
  @Override
  @Nullable
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    ...
      if (this.advised.exposeProxy) {
        // Make invocation available if necessary.
        oldProxy = AopContext.setCurrentProxy(proxy);
        setProxyContext = true;
      }
    ...
    finally {
      if (setProxyContext) {
        // Restore old proxy.
        AopContext.setCurrentProxy(oldProxy);
      }
    }
  }
}

public abstract class AopConfigUtils {
  public static void forceAutoProxyCreatorToUseClassProxying(BeanDefinitionRegistry registry) {
    if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
      BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
      definition.getPropertyValues().add("proxyTargetClass", Boolean.TRUE);
    }
  }
  public static void forceAutoProxyCreatorToExposeProxy(BeanDefinitionRegistry registry) {
    if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
      BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
      definition.getPropertyValues().add("exposeProxy", Boolean.TRUE);
    }
  }
}