IoC容器提供了自动依赖装配的方式，为应用IoC容器提供很大的方便。在自动配置中，不需要显式的去指定Bean属性，只需要配置autowiring属性，IoC容器会根据这个属性配置，使用反射的方式查找属性的类型或者名字，然后基于类型或名字来自动匹配IoC中的Bean,从而完成自动注入的工作。
自动依赖注入的实现部分在AbstractAutowireCapableBeanFactory中的populateBean方法中
//进行依赖注入 if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {MutablePropertyValues newPvs = new MutablePropertyValues(pvs);//根据名字注入// Add property values based on autowire by name if applicable.if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {autowireByName(beanName, mbd, bw, newPvs);}//根据类型注入// Add property values based on autowire by type if applicable.if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {autowireByType(beanName, mbd, bw, newPvs);}pvs = newPvs;}
对autowireMode进行判断后分别调用autowireByName和autowireByType进行注入。
protected void autowireByName(String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);for (String propertyName : propertyNames) {if (containsBean(propertyName)) { //使用当前Bean的属性名，在IoC容器中获取对应的bean，让将获取的bean设置为当前的Bean的属性值。Object bean = getBean(propertyName);pvs.add(propertyName, bean);registerDependentBean(propertyName, beanName);if (logger.isDebugEnabled()) {logger.debug("Added autowiring by name from bean name '" + beanName +"' via property '" + propertyName + "' to bean named '" + propertyName + "'");}}else {if (logger.isTraceEnabled()) {logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName +"' by name: no matching bean found");}}}}
