问题描述
面试问Spring中AOP的原理？用到哪些技术？答：通过动态代理技术，然后简单说了些实现方式。这只是其中的一种，还有其他的吗？答：........求大哥们指点！ 问题补充：suziwen 写道
解决方案
其实它的代理 ：分为动态代理和静态代理
解决方案二：
spring 提供了多种不同的方案实现对 bean 的 aop proxy, 包括 ProxyFactoryBean, 便利的 TransactionProxyFactoryBean 以及 AutoProxyCreator 等, 下图是 proxy class diagram 以供参考这里重点说一下最常用的 ProxyFactoryBean, TransactionProxyFactoryBean, BeanNameAutoProxyCreator, DefaultAdvisorAutoProxyCreator 的联系和区别 1. ProxyFactoryBean : 使用率最高的 proxy 方式, 它通过配置 interceptorNames 属性决定加入哪些 advisor (method interceptor 将会被自动包装成 advisor, 下文将描述这个细节), 注意是 "interceptorNames" 而不是 "interceptors", 原因是 ProxyFactoryBean 可能返回非 singleton 的 proxy 实例, 而 advisior 可能也是非 singleton 的, 因此不能通过 interceptor reference 来注入 2. TransactionProxyFactoryBean : 特定用于 transaction proxy, 注意其 super class 是 AbstractSingletonProxyFactoryBean, 也就是说, TransactionProxyFactoryBean 永远无法返回非 singleton 的 proxy 实例 !!! 如果你需要非 singleton 的 proxy 实例, 请考虑使用 ProxyFactoryBean. 3. BeanNameAutoProxyCreator : 故名思义, 根据 bean name 进行 auto proxy, bean name 的 match 规则参见 org.springframework.util.PatternMatchUtils 4. DefaultAdvisorAutoProxyCreator : 更强大的 auto proxy creator, 强大之处在于它会 cahce 容器中所有注册的 advisor, 然后搜索容器中所有的 bean , 如果某个 bean 满足 advisor 中的 Pointcut, 那么将会被自动代理, 与 BeanNameAutoProxyCreator 相比, 省去了配置 beanNames 的工作, 引用：eg : <bean class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator" /> <bean id="defaultPointcutAdvisor" class="org.springframework.aop.support.DefaultPointcutAdvisor" scope="prototype"> <property name="pointcut" ref="fooPointcut"/> <property name="advice" ref="fooAdvice"/> </bean> <bean id="fooAdvice" class="com.mycompany.FooAdvice" scope="prototype" /> <bean id="fooPointcut" class="org.springframework.aop.support.JdkRegexpMethodPointcut" scope="prototype"> <property name="patterns"> <list> <value>com.mycompany.FooService.*</value> </list> </property> </bean> <bean class="org.springframework.aop.framework.autoproxy.DefaultAdvisorAutoProxyCreator" /> <bean id="defaultPointcutAdvisor" class="org.springframework.aop.support.DefaultPointcutAdvisor" scope="prototype"> <property name="pointcut" ref="fooPointcut"/> <property name="advice" ref="fooAdvice"/></bean><bean id="fooAdvice" class="com.mycompany.FooAdvice" scope="prototype" /><bean id="fooPointcut" class="org.springframework.aop.support.JdkRegexpMethodPointcut" scope="prototype"> <property name="patterns"> <list> <value>com.mycompany.FooService.*</value> </list> </property> </bean> 以上配置将自动代理容器中所有 com.mycompany.FooService 类型的 bean, 并拦截其所有方法 深度话题 1. MethodInterceptor 如何被包装成 Advisor ? 在 AdvisorAdapterRegistry#wrap(Object) 方法中实现, code as below public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException { if (adviceObject instanceof Advisor) { return (Advisor) adviceObject; } if (!(adviceObject instanceof Advice)) { hrow new UnknownAdviceTypeException(adviceObject); } Advice advice = (Advice) adviceObject; if (advice instanceof MethodInterceptor) { // So well-known it doesn't even need an adapter. return new DefaultPointcutAdvisor(advice); } for (int i = 0; i < this.adapters.size(); i++) { / Check that it is supported. AdvisorAdapter adapter = (AdvisorAdapter) this.adapters.get(i); if (adapter.supportsAdvice(advice)) { return new DefaultPointcutAdvisor(advice); } } throw new UnknownAdviceTypeException(advice); } public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException { if (adviceObject instanceof Advisor) { return (Advisor) adviceObject; } if (!(adviceObject instanceof Advice)) { hrow new UnknownAdviceTypeException(adviceObject); } Advice advice = (Advice) adviceObject; if (advice instanceof MethodInterceptor) { // So well-known it doesn't even need an adapter. return new DefaultPointcutAdvisor(advice); } for (int i = 0; i < this.adapters.size(); i++) { / Check that it is supported. AdvisorAdapter adapter = (AdvisorAdapter) this.adapters.get(i);if (adapter.supportsAdvice(advice)) { return new DefaultPointcutAdvisor(advice); }} throw new UnknownAdviceTypeException(advice);} 从代码可以看到, 如果 adviceObject(也就是 interceptorNames 对应的 bean) 不是 advisor 而是 MethodInterceptor 或 Advice, 那么 spring 将其包装成 DefaultPointcutAdvisor, 而 DefaultPointcutAdvisor 中定义的 Pointcut 是 TruePointcut : class TruePointcut implements Pointcut, Serializable { public static final TruePointcut INSTANCE = new TruePointcut(); /** * Enforce Singleton pattern. */ private TruePointcut() { } public ClassFilter getClassFilter() { return ClassFilter.TRUE; } public MethodMatcher getMethodMatcher() { return MethodMatcher.TRUE; } /** * Required to support serialization. Replaces with canonical * instance on deserialization, protecting Singleton pattern. * Alternative to overriding <code>equals()</code>. */ private Object readResolve() { return INSTANCE; } public String toString() { return "Pointcut.TRUE"; } }
解决方案三：
cglib代理