浅析AOP源码（二）

最新推荐文章于 2023-03-31 09:07:11 发布

zero__007

最新推荐文章于 2023-03-31 09:07:11 发布

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本文详细解析了Spring框架中AOP代理的创建过程，包括如何决定使用JDK动态代理还是CGLIB代理，以及代理创建的具体实现细节。

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上一篇https://blog.youkuaiyun.com/zero__007/article/details/80375395，介绍了AbstractAutoProxyCreator中在bean实例化之后会组装成代理对象，然后返回，代理对象的创建在createProxy()方法中：

	protected Object createProxy(
			Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {

		if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
			AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
		}

		ProxyFactory proxyFactory = new ProxyFactory();
		proxyFactory.copyFrom(this);

		if (!proxyFactory.isProxyTargetClass()) {
			if (shouldProxyTargetClass(beanClass, beanName)) {
				proxyFactory.setProxyTargetClass(true);
			}
			else {
				evaluateProxyInterfaces(beanClass, proxyFactory);
			}
		}

		Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
		for (Advisor advisor : advisors) {
			proxyFactory.addAdvisor(advisor);
		}

		proxyFactory.setTargetSource(targetSource);
		customizeProxyFactory(proxyFactory);

		proxyFactory.setFrozen(this.freezeProxy);
		if (advisorsPreFiltered()) {
			proxyFactory.setPreFiltered(true);
		}

		return proxyFactory.getProxy(getProxyClassLoader());
	}

首先会创建一个ProxyFactory对象：

public class ProxyFactory extends ProxyCreatorSupport {

public class ProxyCreatorSupport extends AdvisedSupport {

   private AopProxyFactory aopProxyFactory;

   public ProxyCreatorSupport() {
      this.aopProxyFactory = new DefaultAopProxyFactory();
   }

AopProxyFactory是一个接口，用生成AopProxy：

public interface AopProxyFactory {
   AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException;
}

AopProxy也是一个接口类，它的实现类有CglibAopProxy、JdkDynamicAopProxy、ObjenesisCglibAopProxy。

继续看ProxyFactory#getProxy：

public Object getProxy(ClassLoader classLoader) {
   return createAopProxy().getProxy(classLoader);
}

protected final synchronized AopProxy createAopProxy() {
   if (!this.active) {
      activate();
   }
   return getAopProxyFactory().createAopProxy(this);
}

@Override
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
   if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
      Class<?> targetClass = config.getTargetClass();
      if (targetClass == null) {
         throw new AopConfigException("TargetSource cannot determine target class: " +
               "Either an interface or a target is required for proxy creation.");
      }
      if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
         return new JdkDynamicAopProxy(config);
      }
      return new ObjenesisCglibAopProxy(config);
   }
   else {
      return new JdkDynamicAopProxy(config);
   }
}

在DefaultAopProxyFactory#createAopProxy中，会决定是jdk代理还是cglib代理：
• optimize：代理是否应执行积极的优化，默认为false。
• proxyTargetClass：AopAutoConfiguration中指定，默认为true，也就是选择使用 cglib 代理。proxyTargetClass=true设定
• hasNoUserSuppliedProxyInterfaces：是否没有实现接口