@Aspect @EnableAspectJAutoProxy @Component public class LogAspect { @Pointcut("execution(* org.javaboy.demo.service.*.*(..))") public void pc() { } @Before("pc()") public void before(JoinPoint jp) { String name = jp.getSignature().getName(); System.out.println(name + " 方法开始执行了..."); } }这个切面要拦截的方法是 org.javaboy.demo.service 包下的所有类的所有方法,现在,这个包下有一个 BookService 类,内容如下:
@Service("org.javaboy.demo.service.BookService.ORIGINAL") public class BookService { public void hello() { System.out.println("hello bs"); } }这个 BookService 的 beanName 我没有使用默认的 beanName,而是自己配置了一个 beanName,这个 beanName 的配置方式是 类名的完整路径+.ORIGINAL。
@Override protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException { //省略。。。 try { // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance. Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } } catch (Throwable ex) { throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName, "BeanPostProcessor before instantiation of bean failed", ex); } try { Object beanInstance = doCreateBean(beanName, mbdToUse, args); if (logger.isTraceEnabled()) { logger.trace("Finished creating instance of bean '" + beanName + "'"); } return beanInstance; } //省略。。。 }小伙伴们看,这里的 resolveBeforeInstantiation 方法就是给 BeanPostProcessor 一个返回代理对象的机会,在这个方法中,最终就会触发到 InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation 方法,我们来看看这里涉及到的跟 AOP 相关的 AbstractAutoProxyCreator#postProcessBeforeInstantiation 方法:
@Override 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; }这个方法实际上干了两件事:
2.如果有我们有自定义的 TargetSource,则根据自定义的 TargetSource 去创建代理对象。
@Override protected boolean shouldSkip(Class<?> beanClass, String beanName) { // TODO: Consider optimization by caching the list of the aspect names List<Advisor> candidateAdvisors = findCandidateAdvisors(); for (Advisor advisor : candidateAdvisors) { if (advisor instanceof AspectJPointcutAdvisor pointcutAdvisor && pointcutAdvisor.getAspectName().equals(beanName)) { return true; } } return super.shouldSkip(beanClass, beanName); }这里首先找到系统中所有的切面,找到之后挨个遍历,遍历的时候判断如果当前要创建的 bean 刚好就是切面,那切面肯定是不需要代理的,直接返回 true。否则就会去调用父类的 shouldSkip 方法,我们再来瞅一眼父类的 shouldSkip 方法:
protected boolean shouldSkip(Class<?> beanClass, String beanName) { return AutoProxyUtils.isOriginalInstance(beanName, beanClass); } static boolean isOriginalInstance(String beanName, Class<?> beanClass) { if (!StringUtils.hasLength(beanName) || beanName.length() != beanClass.getName().length() + AutowireCapableBeanFactory.ORIGINAL_INSTANCE_SUFFIX.length()) { return false; } return (beanName.startsWith(beanClass.getName()) && beanName.endsWith(AutowireCapableBeanFactory.ORIGINAL_INSTANCE_SUFFIX)); }父类 shouldSkip 方法主要是调用了一个静态工具方法 isOriginalInstance 来判断当前 bean 是否是一个不需要代理的 bean,这个具体的判断逻辑就是检查这个 beanName 是否按照 类名的完整路径+.ORIGINAL 的方式命名的,如果是则返回 true。