Spring源码探索-核心原理下(AOP、MVC)

「爱情、让人受尽委屈。」 2023-09-25 23:55 42阅读 0赞

#### AOP ####

AOP是在Bean的后置处理器中设置的也就是在初始化Bean的时候（`initializeBean`AOP源码的入口函数）。  
这里重点主要分为两个部分一个是代码织入的部分也就是编译阶段，还有一个就是代码运行阶段。

时序图

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核心代码

`initializeBean`

![format_png 1][]

`applyBeanPostProcessorsAfterInitialization`

这个就是遍历所有的后置处理器，进行一些代码的织入，比如AOP的代码织入

@Override
    public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
          throws BeansException {
    
       Object result = existingBean;
       for (BeanPostProcessor processor : getBeanPostProcessors()) {
          Object current = processor.postProcessAfterInitialization(result, beanName);
          if (current == null) {
             return result;
          }
          result = current;
       }
       return result;
    }
    复制代码

![format_png 2][]

在 `Spring` 中,`BeanPostProcessor`的实现子类非常的多，分别完成不同的操作，如：AOP面向切 面编程的注册通知适配器、`Bean` 对象的数据校验、`Bean` 继承属性、方法的合并等等，我们以最简单的 AOP 切面织入来简单了解其主要的功能。下面我们来分析其中一个创建 AOP 代理对象的子类 `AbstractAutoProxyCreator` 类。该类重写了 `postProcessAfterlnitialization()`方法。

`wrapIfNecessary`

这个方法主要是做一些判断,判断这个类是否需要创建代理类

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
        if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {
            return bean;
        } else if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {
            return bean;
        } else if (!this.isInfrastructureClass(bean.getClass()) && !this.shouldSkip(bean.getClass(), beanName)) {
            Object[] specificInterceptors = this.getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, (TargetSource)null);
            if (specificInterceptors != DO_NOT_PROXY) {
                this.advisedBeans.put(cacheKey, Boolean.TRUE);
                Object proxy = this.createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
                this.proxyTypes.put(cacheKey, proxy.getClass());
                return proxy;
            } else {
                this.advisedBeans.put(cacheKey, Boolean.FALSE);
                return bean;
            }
        } else {
            this.advisedBeans.put(cacheKey, Boolean.FALSE);
            return bean;
        }
    }
    复制代码

`createProxy`

这就是个比较核心的方法了在这里进行代理类的创建以及代码的织入

private Object buildProxy(Class<?> beanClass, @Nullable String beanName, @Nullable Object[] specificInterceptors, TargetSource targetSource, boolean classOnly) {
        BeanFactory var7 = this.beanFactory;
        if (var7 instanceof ConfigurableListableBeanFactory clbf) {
            AutoProxyUtils.exposeTargetClass(clbf, beanName, beanClass);
        }
    
        ProxyFactory proxyFactory = new ProxyFactory();
        proxyFactory.copyFrom(this);
        if (proxyFactory.isProxyTargetClass()) {
            if (Proxy.isProxyClass(beanClass) || ClassUtils.isLambdaClass(beanClass)) {
                Class[] var12 = beanClass.getInterfaces();
                int var8 = var12.length;
    
                for(int var9 = 0; var9 < var8; ++var9) {
                    Class<?> ifc = var12[var9];
                    proxyFactory.addInterface(ifc);
                }
            }
        } else if (this.shouldProxyTargetClass(beanClass, beanName)) {
            proxyFactory.setProxyTargetClass(true);
        } else {
            this.evaluateProxyInterfaces(beanClass, proxyFactory);
        }
    
        Advisor[] advisors = this.buildAdvisors(beanName, specificInterceptors);
        proxyFactory.addAdvisors(advisors);
        proxyFactory.setTargetSource(targetSource);
        this.customizeProxyFactory(proxyFactory);
        proxyFactory.setFrozen(this.freezeProxy);
        if (this.advisorsPreFiltered()) {
            proxyFactory.setPreFiltered(true);
        }
    
        ClassLoader classLoader = this.getProxyClassLoader();
        if (classLoader instanceof SmartClassLoader smartClassLoader) {
            if (classLoader != beanClass.getClassLoader()) {
                classLoader = smartClassLoader.getOriginalClassLoader();
            }
        }
    
        return classOnly ?

[format_png]: https://img-blog.csdnimg.cn/img_convert/681b25129e39a85eeda338db1ebdf3b4.webp?x-oss-process=image/format,png
[format_png 1]: https://img-blog.csdnimg.cn/img_convert/20e5f943ab9baa953d41d3bd770070ff.webp?x-oss-process=image/format,png
[format_png 2]: https://img-blog.csdnimg.cn/img_convert/113586d2ead88b5a36c258c6659b80ee.webp?x-oss-process=image/format,png