【小家Spring】面向切面编程Spring AOP创建代理的方式：ProxyFactoryBean、ProxyFactory、AspectJProxyFactory（JDK Proxy和CGLIB）（下）

@Aspect
class MyAspect {
    @Pointcut("execution(* hello(..))")
    private void beforeAdd() {
    }
    @Before("beforeAdd()")
    public void before1() {
        System.out.println("-----------before-----------");
    }
}

    public static void main(String[] args) {
        AspectJProxyFactory proxyFactory = new AspectJProxyFactory(new HelloServiceImpl());
    // 注意：此处得MyAspect类上面的@Aspect注解必不可少
        proxyFactory.addAspect(MyAspect.class);
        //proxyFactory.setProxyTargetClass(true);//是否需要使用CGLIB代理
        HelloService proxy = proxyFactory.getProxy();
        proxy.hello();
        System.out.println(proxy.getClass()); //class com.sun.proxy.$Proxy6
    }
输出：
-----------before-----------
this is my method~~
class com.sun.proxy.$Proxy6

public class AspectJProxyFactory extends ProxyCreatorSupport {
  /** Cache for singleton aspect instances */
  private static final Map<Class<?>, Object> aspectCache = new ConcurrentHashMap<>();
  //基于AspectJ时,创建Spring AOP的Advice  下面详说
  private final AspectJAdvisorFactory aspectFactory = new ReflectiveAspectJAdvisorFactory();
  public AspectJProxyFactory() {
  }
  public AspectJProxyFactory(Object target) {
    Assert.notNull(target, "Target object must not be null");
    setInterfaces(ClassUtils.getAllInterfaces(target));
    setTarget(target);
  }
  public AspectJProxyFactory(Class<?>... interfaces) {
    setInterfaces(interfaces);
  }
  // 这两个addAspect方法是最重要的：我们可以把一个现有的aspectInstance传进去，当然也可以是一个Class（下面）======
  public void addAspect(Object aspectInstance) {
    Class<?> aspectClass = aspectInstance.getClass();
    String aspectName = aspectClass.getName();
    AspectMetadata am = createAspectMetadata(aspectClass, aspectName);
    // 显然这种直接传实例进来的，默认就是单例的。不是单例我们就报错了~~~~
    if (am.getAjType().getPerClause().getKind() != PerClauseKind.SINGLETON) {
      throw new IllegalArgumentException(
          "Aspect class [" + aspectClass.getName() + "] does not define a singleton aspect");
    }
    // 这个方法就非常的关键了~~~ Singleton...是它MetadataAwareAspectInstanceFactory的子类
    addAdvisorsFromAspectInstanceFactory(
        new SingletonMetadataAwareAspectInstanceFactory(aspectInstance, aspectName));
  }
  public void addAspect(Class<?> aspectClass) {
    String aspectName = aspectClass.getName();
    AspectMetadata am = createAspectMetadata(aspectClass, aspectName);
    MetadataAwareAspectInstanceFactory instanceFactory = createAspectInstanceFactory(am, aspectClass, aspectName);
    addAdvisorsFromAspectInstanceFactory(instanceFactory);
  }
  // 从切面工厂里，把对应切面实例里面的增强器（通知）都获取到~~~
  private void addAdvisorsFromAspectInstanceFactory(MetadataAwareAspectInstanceFactory instanceFactory) {
    // 从切面工厂里，先拿到所有的增强器们~~~
    List<Advisor> advisors = this.aspectFactory.getAdvisors(instanceFactory);
    Class<?> targetClass = getTargetClass();
    Assert.state(targetClass != null, "Unresolvable target class");
    advisors = AopUtils.findAdvisorsThatCanApply(advisors, targetClass);
    AspectJProxyUtils.makeAdvisorChainAspectJCapableIfNecessary(advisors);
    AnnotationAwareOrderComparator.sort(advisors);
    addAdvisors(advisors);
  }
}