属性扫描完成之后, 就可以开始属性注入了.
代码块:
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#doCreateBean
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences && isSingletonCurrentlyInCreation(beanName)); if (earlySingletonExposure) { if (logger.isTraceEnabled()) { logger.trace("Eagerly caching bean '" + beanName + "' to allow for resolving potential circular references"); } //这里创建了一个匿名的 ObjectFactory 实现类, 他是一个工厂, 可以用来获取对象 //addSingletonFactory中, 将这个工厂放到 singletonFactories 中去了. singletonFactories 是spring的三级缓存 addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean)); } // Initialize the bean instance. Object exposedObject = bean; try { //设置属性,非常重要 populateBean(beanName, mbd, instanceWrapper); //执行后置处理器,aop就是在这里完成的处理 exposedObject = initializeBean(beanName, exposedObject, mbd); }
这里只看 populateBean() 方法
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#populateBean
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) { if (bw == null) { if (mbd.hasPropertyValues()) { throw new BeanCreationException( mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance"); } else { // Skip property population phase for null instance. return; } } // Give any InstantiationAwareBeanPostProcessors the opportunity to modify the // state of the bean before properties are set. This can be used, for example, // to support styles of field injection. // 需不需要spring来设置属性 // 实例化之后的 bean的后置处理器 // org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor#postProcessAfterInstantiation if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; //如果返回为 false, 则会终止属性注入 if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) { return; } } } } PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null); int resolvedAutowireMode = mbd.getResolvedAutowireMode(); //如果给一个类设置了 : AUTOWIRE_BY_NAME 和 AUTOWIRE_BY_TYPE, 那么类中的属性, 会根据规则自动注入, 而不需要@Autowired或@Resource了 //默认情况下, 是 AUTOWIRE_NO, 所以这里默认是不执行 if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) { MutablePropertyValues newPvs = new MutablePropertyValues(pvs); // Add property values based on autowire by name if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_NAME) { autowireByName(beanName, mbd, bw, newPvs); } // Add property values based on autowire by type if applicable. if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) { autowireByType(beanName, mbd, bw, newPvs); } pvs = newPvs; } boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors(); //深度引用检查, 引用再引用 boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE); PropertyDescriptor[] filteredPds = null; if (hasInstAwareBpps) { if (pvs == null) { pvs = mbd.getPropertyValues(); } for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; //这里也是调用的实例化后的后置处理器, 只是调用的方法不一样 PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName); if (pvsToUse == null) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); }
//这里的 postProcessPropertyValues 是一个过时方法 pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName); if (pvsToUse == null) { return; } } pvs = pvsToUse; } } } if (needsDepCheck) { if (filteredPds == null) { filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching); } checkDependencies(beanName, mbd, filteredPds, pvs); } if (pvs != null) { applyPropertyValues(beanName, mbd, bw, pvs); } }
上面的注释里面说到, spring默认使用 AUTOWIRE_NO 模式, 那属性注入方法 autowireByName 和 autowireByType 都没进去.
也没看到别的属性注入方法了, 那么, 这里是怎么注入的呢?
要想弄明白这个问题, 得先弄明白里面调用了两次后置处理器的方法, 都干了些什么.
postProcessAfterInstantiation
https://www.cnblogs.com/elvinle/p/13384114.html
postProcessProperties
https://www.cnblogs.com/elvinle/p/13384328.html
postProcessProperties 就是进行 @Autowired 和 @Resource 注入的.
注意到这里, AUTOWIRE_BY_NAME 和 AUTOWIRE_BY_TYPE 是在 他们之前 执行的 .