自動代理抽象：

public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware

這個利用spring 後置處理器來攔截bean建立，在bean的建立過程中，可以通過spring的後置處理器來處理bean的建立過程，SmartInstantiationAwareBeanPostProcessor是InstantiationAwareBeanPostProcessor BeanPostProcessor　的子介面，它的實現類有機會被spring在建立bean例項前後，例項化前後執行指定的方法。

@Override
// bean 例項化前的攔截器
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
    Object cacheKey = getCacheKey(beanClass, beanName);

    if (!StringUtils.hasLength(beanName) || !this.targetSourcedBeans.contains(beanName)) {
        if (this.advisedBeans.containsKey(cacheKey)) {
            
 
return null;
        }
        if (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) {
            this.advisedBeans.put(cacheKey, Boolean.FALSE);
            return null;
        }
    }

    // Create proxy here if we have a custom TargetSource.
    // Suppresses unnecessary default instantiation of the target bean:
    
 
// The TargetSource will handle target instances in a custom fashion.
    TargetSource targetSource = getCustomTargetSource(beanClass, beanName);
    if (targetSource != null) {
        if (StringUtils.hasLength(beanName)) {
            this.targetSourcedBeans.add(beanName);
        }
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
        Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
        this.proxyTypes.put(cacheKey, proxy.getClass());
        return proxy;
    }

    return null;
}


@Override
// 初始化後的攔截器，可以返回一個新物件代替初始化後的物件
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
    if (bean != null) {
        Object cacheKey = getCacheKey(bean.getClass(), beanName);
        // 這個是判斷是否已經被代理過
        if (this.earlyProxyReferences.remove(cacheKey) != bean) {
            // 這個是判斷是否需要包裝，並返回結果的方法
            return wrapIfNecessary(bean, beanName, cacheKey);
        }
    }
    return bean;
}
// 具體的代理邏輯
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
    if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
        return bean;
    }
    if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
        return bean;
    }
    if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {
        this.advisedBeans.put(cacheKey, Boolean.FALSE);
        return bean;
    }

    // Create proxy if we have advice.
    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
    if (specificInterceptors != DO_NOT_PROXY) {
        this.advisedBeans.put(cacheKey, Boolean.TRUE);
        Object proxy = createProxy(
                bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
        this.proxyTypes.put(cacheKey, proxy.getClass());
        return proxy;
    }

    this.advisedBeans.put(cacheKey, Boolean.FALSE);
    return bean;
}

使用示例：

/**
 * @author liangjunhui
 * @date Created in 2020-08-20 9:09
 */
@Configuration
public class MyBeanNameApc {
    @Bean
    public MethodBeforeAdvice methodBeforeAdvice(){
        MethodBeforeAdvice beforeAdvice = (method, args, target) -> System.out.println("前置增強");
        return beforeAdvice;
    }
    @Bean
    public BeanNameAutoProxyCreator beanNameAutoProxyCreator(){
        BeanNameAutoProxyCreator creator = new BeanNameAutoProxyCreator();
        creator.setBeanNames("*ultar");
        creator.setInterceptorNames("methodBeforeAdvice");
        return creator;
    }
    @Bean
    public Mathcalcultar mathcalcultar(){
        return new Mathcalcultar();
    }

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(MyBeanNameApc.class);
        Mathcalcultar bean = context.getBean(Mathcalcultar.class);
        bean.div(1,1);
    }
}

1、將AbstractAutoProxyCreator例項注入到容器，這個例項會攔截bean的建立

2、然後看AbstractAutoProxyCreator#getAdvicesAndAdvisorsForBean在子類的實現，按照子類的匹配規則設定一些資料來，然後apc判斷是否需要產生代理