Spring读源码系列之AOP--02---aop基本概念扫盲---下

public interface Advisor {

	//@since 5.0 Spring5以后才有的  空通知  一般当作默认值
	Advice EMPTY_ADVICE = new Advice() {};
	
	// 该Advisor 持有的通知器
	Advice getAdvice();
	// 这个有点意思：Spring所有的实现类都是return true(官方说暂时还没有应用到)
	// 注意：生成的Advisor是单例还是多例不由isPerInstance()的返回结果决定，而由自己在定义bean的时候控制
	// 理解：和类共享（per-class）或基于实例（per-instance）相关  类共享：类比静态变量   实例共享：类比实例变量
	boolean isPerInstance();

}

public interface PointcutAdvisor extends Advisor {
	Pointcut getPointcut();
}

// 实现了 Ordered接口
public abstract class AbstractPointcutAdvisor implements PointcutAdvisor, Ordered, Serializable {
	// 调用者可以手动来指定Order
	public void setOrder(int order) {
		this.order = order;
	}
	
	@Override
	public int getOrder() {
		if (this.order != null) {
			return this.order;
		}
		
		// 若调用者没有指定Order，那就拿advice的order为准（若有），否则LOWEST_PRECEDENCE表示最后执行
		Advice advice = getAdvice();
		if (advice instanceof Ordered) {
			return ((Ordered) advice).getOrder();
		}
		return Ordered.LOWEST_PRECEDENCE;
	}
	// Spring还没有使用该属性 永远返回true了
	@Override
	public boolean isPerInstance() {
		return true;
	}
	...
}

public abstract class AbstractGenericPointcutAdvisor extends AbstractPointcutAdvisor {
	private Advice advice = EMPTY_ADVICE;
	public void setAdvice(Advice advice) {
		this.advice = advice;
	}
	@Override
	public Advice getAdvice() {
		return this.advice;
	}
	...
}

public class DefaultPointcutAdvisor extends AbstractGenericPointcutAdvisor implements Serializable {

	private Pointcut pointcut = Pointcut.TRUE;

	public DefaultPointcutAdvisor() {
	}

	public DefaultPointcutAdvisor(Advice advice) {
		this(Pointcut.TRUE, advice);
	}

	public DefaultPointcutAdvisor(Pointcut pointcut, Advice advice) {
		this.pointcut = pointcut;
		setAdvice(advice);
	}

	public void setPointcut(@Nullable Pointcut pointcut) {
		this.pointcut = (pointcut != null ? pointcut : Pointcut.TRUE);
	}

	@Override
	public Pointcut getPointcut() {
		return this.pointcut;
	}
	...
}

// 实现了BeanFactoryAware接口，若在Bean容器里注册可以注入BeanFactory~~~从而访问里面的实例
public abstract class AbstractBeanFactoryPointcutAdvisor extends AbstractPointcutAdvisor implements BeanFactoryAware {
	
	// 我们发现这两个都是@Nullable，所以他们脱离容器使用也是可以的
	@Nullable
	private String adviceBeanName;
	@Nullable
	private BeanFactory beanFactory;
	
	@Nullable
	private transient volatile Advice advice;
	
	public void setAdviceBeanName(@Nullable String adviceBeanName) {
		this.adviceBeanName = adviceBeanName;
	}
	@Override
	public void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
		// 若在Spring环境下，会给AdviceMonitor重新赋值为：getSingletonMutex()
		resetAdviceMonitor();
	}
	
	// 此处加锁
	public void setAdvice(Advice advice) {
		synchronized (this.adviceMonitor) {
			this.advice = advice;
		}
	}

	// 这是它最重要的方法，获取增强器
	@Override
	public Advice getAdvice() {
		Advice advice = this.advice;
		// 非Spring环境一般手动set进来，所以就直接返回吧
		if (advice != null) {
			return advice;
		}

		//显然进来Spring容器环境了，bean工厂和beanName都是不能为null的
		Assert.state(this.adviceBeanName != null, "'adviceBeanName' must be specified");
		Assert.state(this.beanFactory != null, "BeanFactory must be set to resolve 'adviceBeanName'");
		
		// 若bean是单例的  那就没什么好说的  直接去工厂里拿出来就完事了（Advice.class）  有可能返回null哦
		if (this.beanFactory.isSingleton(this.adviceBeanName)) {
			advice = this.beanFactory.getBean(this.adviceBeanName, Advice.class);
			this.advice = advice;
			return advice;
		}
		// 若是多例的，就加锁  然后调用getBean()给他生成一个新的实例即可
		else {
			synchronized (this.adviceMonitor) {
				//这步赋值和判断不能省~~~确保万无一失
				advice = this.advice;
				if (advice == null) {
					advice = this.beanFactory.getBean(this.adviceBeanName, Advice.class);
					this.advice = advice;
				}
				return advice;
			}
		}
	}
}

public class DefaultBeanFactoryPointcutAdvisor extends AbstractBeanFactoryPointcutAdvisor {
	private Pointcut pointcut = Pointcut.TRUE;

	// 若传进来为null，还是选择 Pointcut.TRUE 匹配所有
	public void setPointcut(@Nullable Pointcut pointcut) {
		this.pointcut = (pointcut != null ? pointcut : Pointcut.TRUE);
	}
	@Override
	public Pointcut getPointcut() {
		return this.pointcut;
	}
}

// @since 3.1  毕竟Spring的整个org.springframework.cache.Cache体系都是从这里开始的。（@Cacheable...等等）
public class BeanFactoryCacheOperationSourceAdvisor extends AbstractBeanFactoryPointcutAdvisor {

	// 显然它最重要的是持有这个引用,后面cache系列会详细讲解
	@Nullable
	private CacheOperationSource cacheOperationSource;

	// Pointcut使用的是CacheOperationSourcePointcut
	private final CacheOperationSourcePointcut pointcut = new CacheOperationSourcePointcut() {
		@Override
		@Nullable
		protected CacheOperationSource getCacheOperationSource() {
			return cacheOperationSource;
		}
	};


	public void setCacheOperationSource(CacheOperationSource cacheOperationSource) {
		this.cacheOperationSource = cacheOperationSource;
	}
	public void setClassFilter(ClassFilter classFilter) {
		this.pointcut.setClassFilter(classFilter);
	}
	@Override
	public Pointcut getPointcut() {
		return this.pointcut;
	}

}

public class AsyncAnnotationAdvisor extends AbstractPointcutAdvisor implements BeanFactoryAware {
	// 处理异步发生的异常的====
	private AsyncUncaughtExceptionHandler exceptionHandler;
	
	private Advice advice;
	private Pointcut pointcut;

	// 构造函数们
	public AsyncAnnotationAdvisor() {
		this(null, null);
	}
	// executor：可以自己指定异步任务的执行器
	// exceptionHandler：异步异常的处理器
	public AsyncAnnotationAdvisor(@Nullable Executor executor, @Nullable AsyncUncaughtExceptionHandler exceptionHandler) {
		Set<Class<? extends Annotation>> asyncAnnotationTypes = new LinkedHashSet<>(2);
		asyncAnnotationTypes.add(Async.class);
		
		// 支持EJB的注解：@Asynchronous
		try {
			asyncAnnotationTypes.add((Class<? extends Annotation>)
					ClassUtils.forName("javax.ejb.Asynchronous", AsyncAnnotationAdvisor.class.getClassLoader()));
		} catch (ClassNotFoundException ex) {
			// If EJB 3.1 API not present, simply ignore.
		}
		if (exceptionHandler != null) {
			this.exceptionHandler = exceptionHandler;
		} else {
			// SimpleAsyncUncaughtExceptionHandler：只是一个简单的logger.error的输入打印
			this.exceptionHandler = new SimpleAsyncUncaughtExceptionHandler();
		}
		
		// buildAdvice: new AnnotationAsyncExecutionInterceptor(executor, exceptionHandler)   它是个MethodInterceptor  环绕通知器
		this.advice = buildAdvice(executor, this.exceptionHandler);
		// 把asyncAnnotationTypes交给buildPointcut，它最终是个ComposablePointcut，会把这两种注解都支持。union起来 或者的关系
		this.pointcut = buildPointcut(asyncAnnotationTypes);
	}

	public void setTaskExecutor(Executor executor) {
		this.advice = buildAdvice(executor, this.exceptionHandler);
	}
	...
}

public class AspectJPointcutAdvisor implements PointcutAdvisor, Ordered {
	
	//AbstractAspectJAdvice通知：它的子类看下面截图，就非常清楚了
	private final AbstractAspectJAdvice advice;
	//可以接受任意的Pointcut，可谓非常的通用（当然也包含切点表达式啦）
	private final Pointcut pointcut;

	@Nullable
	private Integer order;
	
	//只有这一个构造函数，包装一个advice
	public AspectJPointcutAdvisor(AbstractAspectJAdvice advice) {
		Assert.notNull(advice, "Advice must not be null");
		this.advice = advice;
		// 然后pointcut根据advice直接给生成了一个。这是AbstractAspectJAdvice#buildSafePointcut的方法
		this.pointcut = advice.buildSafePointcut();
	}
...
}

	public final Pointcut buildSafePointcut() {
	//拿到AbstractAspectJAdvice内部维护的AspectJExpressionPointcut pointcut
		Pointcut pc = getPointcut();
		MethodMatcher safeMethodMatcher = MethodMatchers.intersection(
				new AdviceExcludingMethodMatcher(this.aspectJAdviceMethod), pc.getMethodMatcher());
		return new ComposablePointcut(pc.getClassFilter(), safeMethodMatcher);
	}

// 由SpringAOP顾问包装AspectJ实现的接口 可能具有延迟初始化策略的方面。
// 例如，一个PerThis实例化模型意味着对建议的初始化太慢
public interface InstantiationModelAwarePointcutAdvisor extends PointcutAdvisor {

	// 该Advisor是否需要懒加载
	boolean isLazy();
	// 判断此Advisor它所拥有的Advice是否已经初始化了
	boolean isAdviceInstantiated();
}

// 默认的访问权限，显然是Spring内部自己用的
class InstantiationModelAwarePointcutAdvisorImpl
		implements InstantiationModelAwarePointcutAdvisor, AspectJPrecedenceInformation, Serializable {
	private static final Advice EMPTY_ADVICE = new Advice() {};
	// 和AspectJExpression
	private final AspectJExpressionPointcut declaredPointcut;
	..
	
	// 通知方法
	private transient Method aspectJAdviceMethod;
	
	private final AspectJAdvisorFactory aspectJAdvisorFactory;
	private final MetadataAwareAspectInstanceFactory aspectInstanceFactory;

	@Nullable
	private Advice instantiatedAdvice;
	@Nullable
	private Boolean isBeforeAdvice;
	@Nullable
	private Boolean isAfterAdvice;
	
	...
	@Override
	public boolean isPerInstance() {
		return (getAspectMetadata().getAjType().getPerClause().getKind() != PerClauseKind.SINGLETON);
	}
	@Override
	public synchronized Advice getAdvice() {
	//第一次获取Adivce时，才去创建---懒加载
		if (this.instantiatedAdvice == null) {
			this.instantiatedAdvice = instantiateAdvice(this.declaredPointcut);
		}
		return this.instantiatedAdvice;
	}
	
	// advice 由aspectJAdvisorFactory去生产  懒加载的效果
	private Advice instantiateAdvice(AspectJExpressionPointcut pointcut) {
		Advice advice = this.aspectJAdvisorFactory.getAdvice(this.aspectJAdviceMethod, pointcut,
				this.aspectInstanceFactory, this.declarationOrder, this.aspectName);
		return (advice != null ? advice : EMPTY_ADVICE);
	}

	@Override
	public boolean isBeforeAdvice() {
		if (this.isBeforeAdvice == null) {
			determineAdviceType();
		}
		return this.isBeforeAdvice;
	}
	@Override
	public boolean isAfterAdvice() {
		if (this.isAfterAdvice == null) {
			determineAdviceType();
		}
		return this.isAfterAdvice;
	}
	
	// 这里解释根据@Aspect方法上标注的注解，来区分这两个字段的值的
	private void determineAdviceType() {
		AspectJAnnotation<?> aspectJAnnotation =
				AbstractAspectJAdvisorFactory.findAspectJAnnotationOnMethod(this.aspectJAdviceMethod);
		if (aspectJAnnotation == null) {
			this.isBeforeAdvice = false;
			this.isAfterAdvice = false;
		}
		else {
			switch (aspectJAnnotation.getAnnotationType()) {
				case AtAfter:
				case AtAfterReturning:
				case AtAfterThrowing:
					this.isAfterAdvice = true;
					this.isBeforeAdvice = false;
					break;
				case AtAround:
				case AtPointcut:
					this.isAfterAdvice = false;
					this.isBeforeAdvice = false;
					break;
				case AtBefore:
					this.isAfterAdvice = false;
					this.isBeforeAdvice = true;
			}
		}
	}
	....
}

//This interface cannot be implemented directly; 
//subinterfaces must provide the advice type implementing the introduction.
//Introduction is the implementation of additional interfaces (not implemented by a target) via AOP advice
//重点在最后一句话: Introduction才是这些附加接口的实现类,而不是目标对象通过增强方法去实现
public interface IntroductionAdvisor extends Advisor, IntroductionInfo {

	/**
	 * Return the filter determining which target classes this introduction
	 * should apply to.
	 * This represents the class part of a pointcut. Note that method
	 * matching doesn't make sense to introductions.
	 */
	ClassFilter getClassFilter();

	/**
	 * Can the advised interfaces be implemented by the introduction advice?
	 * Invoked before adding an IntroductionAdvisor.
	 */
	void validateInterfaces() throws IllegalArgumentException;

}

// 提供描述引言所需信息的接口
// IntroductionAdvisor必须实现这个接口。若`org.aopalliance.aop.Advice`直接实现了此接口，
// 它可以独立的当作introduction来使用而不用依赖IntroductionAdvisor。这种情况下，这个advice可议自描述，不仅提供必要的行为，而且描述它引入的接口。
public interface IntroductionInfo {
	//Return the additional interfaces introduced by this Advisor or Advice.
	// 返回额外给Advisor 或者 advice实现的接口们
	Class<?>[] getInterfaces();
}

// IntroductionInterceptor它是对MethodInterceptor的一个扩展，
//同时他还继承了接口DynamicIntroductionAdvice
public interface IntroductionInterceptor extends MethodInterceptor, DynamicIntroductionAdvice {	
}

public interface DynamicIntroductionAdvice extends Advice {
	boolean implementsInterface(Class<?> intf);
}

// 定义一个新的行为接口，这个行为准备作用在目标对象上
public interface IOtherInte {
    void doOther();
}
// 自己定义一个IntroductionInterceptor来实现IntroductionInterceptor接口
// 注意：此处也实现了接口IOtherInte（这是类似于增强器部分）  相当于这个interptor目前就只处理 IOtherInte
public class SomeInteIntroductionInterceptor implements IntroductionInterceptor, IOtherInte {
    /**
     * 判断调用的方法是否为指定类中的方法
     * 如果Method代表了一个方法 那么调用它的invoke就相当于执行了它代表的这个方法
     */
    @Override
    public Object invoke(MethodInvocation invocation) throws Throwable {
        if (implementsInterface(invocation.getMethod().getDeclaringClass())) {
            System.out.println("我是引介增强的方法体~~~invoke");
            return invocation.getMethod().invoke(this, invocation.getArguments());
        }
        return invocation.proceed();
    }

    /**
     * 判断clazz是否为给定接口IOtherBean的实现
     */
    @Override
    public boolean implementsInterface(Class clazz) {
        return clazz.isAssignableFrom(IOtherInte.class);
    }

    @Override
    public void doOther() {
        System.out.println("给人贴标签 doOther...");
    }
}

// 方法测试
    public static void main(String[] args) {
        ProxyFactory factory = new ProxyFactory(new Person());
        factory.setProxyTargetClass(true); // 强制私用CGLIB 以保证我们的Person方法也能正常调用

        // 此处采用IntroductionInterceptor 这个引介增强的拦截器
        Advice advice = new SomeInteIntroductionInterceptor();

        // 切点+通知（注意：此处放的是复合切面）
        Advisor advisor = new DefaultIntroductionAdvisor((DynamicIntroductionAdvice) advice, IOtherInte.class);
        //Advisor advisor = new DefaultPointcutAdvisor(cut, advice);
        factory.addAdvisor(advisor);

        IOtherInte otherInte = (IOtherInte) factory.getProxy();
        otherInte.doOther();

        System.out.println("===============================");

        // Person本身自己的方法  也得到了保留
        Person p = (Person) factory.getProxy();
        p.run();
        p.say();
    }

输出：
我是引介增强的方法体~~~invoke
给人贴标签 doOther...
===============================
我在run...
我在say...

// 它是一个Advisor，同时也是一个IntroductionInfo 
public interface IntroductionAdvisor extends Advisor, IntroductionInfo {
	
	// 它只有ClassFilter，因为它只能作用在类层面上
	ClassFilter getClassFilter();
	// 判断这些接口，是否真的能够增强。  DynamicIntroductionAdvice#implementsInterface()方法
	void validateInterfaces() throws IllegalArgumentException;

}

// 它直接事IntroductionAdvisor的实现类。同时也是一个ClassFilter
public class DefaultIntroductionAdvisor implements IntroductionAdvisor, ClassFilter, Ordered, Serializable {
	private final Advice advice;

	private final Set<Class<?>> interfaces = new LinkedHashSet<>();
	private int order = Ordered.LOWEST_PRECEDENCE;
    
	// 构造函数们
	public DefaultIntroductionAdvisor(Advice advice) {
		this(advice, (advice instanceof IntroductionInfo ? (IntroductionInfo) advice : null));
	}
	
	// 如果IntroductionInfo 不等于null，就会把接口都add进去/
	// IntroductionInfo 的实现类有常用的：DelegatingIntroductionInterceptor和DelegatePerTargetObjectIntroductionInterceptor
	public DefaultIntroductionAdvisor(Advice advice, @Nullable IntroductionInfo introductionInfo) {
		Assert.notNull(advice, "Advice must not be null");
		this.advice = advice;
		if (introductionInfo != null) {
			Class<?>[] introducedInterfaces = introductionInfo.getInterfaces();
			if (introducedInterfaces.length == 0) {
				throw new IllegalArgumentException("IntroductionAdviceSupport implements no interfaces");
			}
			for (Class<?> ifc : introducedInterfaces) {
				addInterface(ifc);
			}
		}
	}
	
	//当然你也可以不使用IntroductionInfo，而自己手动指定了这个接口
	public DefaultIntroductionAdvisor(DynamicIntroductionAdvice advice, Class<?> intf) {
		Assert.notNull(advice, "Advice must not be null");
		this.advice = advice;
		addInterface(intf);
	}
	...
	@Override
	public void validateInterfaces() throws IllegalArgumentException {
		for (Class<?> ifc : this.interfaces) {
			if (this.advice instanceof DynamicIntroductionAdvice &&
			//advice来实现interfaces---这里是IntroductionInterceptor
					!((DynamicIntroductionAdvice) this.advice).implementsInterface(ifc)) {
			 throw new IllegalArgumentException("DynamicIntroductionAdvice [" + this.advice + "] " +
					 "does not implement interface [" + ifc.getName() + "] specified for introduction");
			}
		}
	}
	...
	
}

public class DelegatingIntroductionInterceptor extends IntroductionInfoSupport
		implements IntroductionInterceptor {
	
	
	/**
	 * Object that actually implements the interfaces.
	 * May be "this" if a subclass implements the introduced interfaces.
	 */
	@Nullable
	private Object delegate;
	
	/**
	 * Construct a new DelegatingIntroductionInterceptor.
	 * The delegate will be the subclass, which must implement
	 * additional interfaces.
	 * 访问权限事protected，显然就是说子类必须去继承这个类，然后提供空构造函数。代理类就是this
	 */
	protected DelegatingIntroductionInterceptor() {
		init(this);
	}
	
	// Construct a new DelegatingIntroductionInterceptor, 
	//providing a delegate that implements the interfaces to be introduced.
	public DelegatingIntroductionInterceptor(Object delegate) {
		init(delegate);
	}
	private void init(Object delegate) {
		Assert.notNull(delegate, "Delegate must not be null");
		this.delegate = delegate;
		implementInterfacesOnObject(delegate);
		
		// 移除调这些内部标记的接口们
		// We don't want to expose the control interface
		suppressInterface(IntroductionInterceptor.class);
		suppressInterface(DynamicIntroductionAdvice.class);
	}
	
	// 如果你要自定义一些行为：比如环绕通知之类的，子类需要复写此方法（否则没有必要了）
	@Override
	@Nullable
	public Object invoke(MethodInvocation mi) throws Throwable {
		// 判断是否是引介增强
		//即当前需要执行的方法,是否是新增接口里面的方法
		if (isMethodOnIntroducedInterface(mi)) {
		//通过反射调用实现了新增接口的代理对象中接口的方法
			Object retVal = AopUtils.invokeJoinpointUsingReflection(this.delegate, mi.getMethod(), mi.getArguments());
			// 如果返回值就是delegate 本身，那就把本身返回出去
			if (retVal == this.delegate && mi instanceof ProxyMethodInvocation) {
				Object proxy = ((ProxyMethodInvocation) mi).getProxy();
				if (mi.getMethod().getReturnType().isInstance(proxy)) {
					retVal = proxy;
				}
			}
			return retVal;
		}
        //如果执行的并非新增接口中的方法，那么直接通过，让剩余拦截器去处理
		return doProceed(mi);
	}
	...
}

// 因为我们继承自DelegatingIntroductionInterceptor，所以若我们不做环绕通知个性化，只需要实现接口的方法即可
public class SomeInteIntroductionInterceptor extends DelegatingIntroductionInterceptor implements IOtherInte {
    @Override
    public void doOther() {
        System.out.println("给人贴标签 doOther...");
    }
}

1: 可以删除掉SomeInteIntroductionInterceptor类了
2：单独实现引介接口
public class OtherImpl implements IOtherInte {

    @Override
    public void doOther() {
        System.out.println("我是OtherImpl");
    }
}
main方法里修改如下：这样就ok了
Advice advice = new DelegatePerTargetObjectIntroductionInterceptor(OtherImpl.class, IOtherInte.class);