SpringAOP联盟（7）-基础的自动代理（AnnotationAwareAspectJAutoProxyCreator）

DefaultAdvisorAutoProxyCreator和AspectJAwareAdvisorAutoProxyCreator均实现了AbstractAdvisorAutoProxyCreator接口。

自动代理实现的核心：在Spring容器中，bean找到“合格”Advisor。

在上文中可知，寻找Bean上“合格”的Advisors是AbstractAutoProxyCreator定义的抽象getAdvicesAndAdvisorsForBean方法。具体逻辑由子类实现。

而真正实现被代理类与增强器解耦的自动代理器，实际上是AbstractAdvisorAutoProxyCreator去完成的。

1. 子类是否允许：子类可实现isEligibleAdvisorBean(beanName)方法，对Spring容器中所有的Advisor类进行初次筛选。
2. Advisor是否切入了Bean：每个Advisor（增强器）会根据Pointcut（切点）使用ClassFilter判断被代理类是否满足规则；使用MethodMatcher判断被代理类是否有方法满足规则；

当然在获得Bean上合格的Advisors后，Spring允许子类进行扩展和排序。

测试方法

@Slf4j
public class TService {
    public void run1() {
        System.out.println("This is a run1() Method!");
    }
    @Transactional
    public void say() {
        log.info("说话...");
    }
}

@Configuration
@EnableTransactionManagement//注册了ProxyTransactionManagementConfiguration
public class MyConfig {
    @Bean("tService")
    public TService tService() {
        return new TService();
    }
}

public class TestSpringProxy {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext =
                new AnnotationConfigApplicationContext(MyConfig.class);
        //可以使用@Primary指定元素，或直接使用name名获取。
        TService bean = (TService)applicationContext.getBean("tService");
        bean.say();
    }
}

源码分析

InfrastructureAdvisorAutoProxyCreator实现了isEligibleAdvisorBean(beanName)方法，即检索出Spring中符合“要求”所有的Advisor。

public class InfrastructureAdvisorAutoProxyCreator extends AbstractAdvisorAutoProxyCreator {
    @Nullable
    private ConfigurableListableBeanFactory beanFactory;
    @Override
    protected void initBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        super.initBeanFactory(beanFactory);
        this.beanFactory = beanFactory;
    }
    //在Spring容器中获取Advisor的Bean，然后判断是否是内部的bean对象。
    @Override
    protected boolean isEligibleAdvisorBean(String beanName) {
        return (this.beanFactory != null && this.beanFactory.containsBeanDefinition(beanName) &&
                this.beanFactory.getBeanDefinition(beanName).getRole() == BeanDefinition.ROLE_INFRASTRUCTURE);
    }
}

而实际上，事务的Advisor和Advice均由Spring完成注册。

@Configuration
public class ProxyTransactionManagementConfiguration extends AbstractTransactionManagementConfiguration {
    //注册了Advisor
    @Bean(name = TransactionManagementConfigUtils.TRANSACTION_ADVISOR_BEAN_NAME)
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)  //声明的role为基础类（Spring内部使用的类）
    public BeanFactoryTransactionAttributeSourceAdvisor transactionAdvisor() {
        BeanFactoryTransactionAttributeSourceAdvisor advisor = new BeanFactoryTransactionAttributeSourceAdvisor();
        advisor.setTransactionAttributeSource(transactionAttributeSource());
        advisor.setAdvice(transactionInterceptor());
        if (this.enableTx != null) {
            advisor.setOrder(this.enableTx.<Integer>getNumber("order"));
        }
        return advisor;
    }

    @Bean
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public TransactionAttributeSource transactionAttributeSource() {
        return new AnnotationTransactionAttributeSource();
    }
    //注册了Advice
    @Bean
    @Role(BeanDefinition.ROLE_INFRASTRUCTURE)
    public TransactionInterceptor transactionInterceptor() {
        TransactionInterceptor interceptor = new TransactionInterceptor();
        interceptor.setTransactionAttributeSource(transactionAttributeSource());
        if (this.txManager != null) {
            interceptor.setTransactionManager(this.txManager);
        }
        return interceptor;
    }
}