@Autowired注入源码

大概流程图

AbstractBeanFactory

if (mbd.isSingleton()) { //是否单例 注意下面是否先执行()-> 代码 也就是ObjectFactory
sharedInstance = getSingleton(beanName, () -> { //单例情况下  这里会把单例实例放到一级缓存 先调用getSingleton 然后调用createBean
					   try {
							return createBean(beanName, mbd, args); // singletonFactory.getObject() 调用的时候 执行这里 getSingleton(String beanName, ObjectFactory<?> singletonFactory)
						}
						catch (BeansException ex) {
							// Explicitly remove instance from singleton cache: It might have been put there
							// eagerly by the creation process, to allow for circular reference resolution.
							// Also remove any beans that received a temporary reference to the bean.
							destroySingleton(beanName);
							throw ex;
						}
					});
					bean = getObjectForBeanInstance(sharedInstance, name, beanName				, mbd);
}

 

AbstractAutowireCapableBeanFactory

@Override
	protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
			throws BeanCreationException {

......................

try { // *****    重头戏，创建 bean
			Object beanInstance = doCreateBean(beanName, mbdToUse, args);
			if (logger.isTraceEnabled()) {
				logger.trace("Finished creating instance of bean '" + beanName + "'");
			}
			return beanInstance;
		}

......................

}

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
		try {
			Object beanInstance;
			final BeanFactory parent = this;
			if (System.getSecurityManager() != null) {
				beanInstance = AccessController.doPrivileged((PrivilegedAction<Object>) () ->
						getInstantiationStrategy().instantiate(mbd, beanName, parent),
						getAccessControlContext());
			}
			else {
				beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent); //实例化
			}
			BeanWrapper bw = new BeanWrapperImpl(beanInstance);
			initBeanWrapper(bw); // 设置ConversionService   注册PropertyEditor
			return bw;
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					mbd.getResourceDescription(), beanName, "Instantiation of bean failed", ex);
		}
	}

 

DefaultSingletonBeanRegistry

protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
		Assert.notNull(singletonFactory, "Singleton factory must not be null");
		synchronized (this.singletonObjects) {
			if (!this.singletonObjects.containsKey(beanName)) { // 一级缓存不存在
				this.singletonFactories.put(beanName, singletonFactory);  // 放入三级缓存
				this.earlySingletonObjects.remove(beanName);  //二级缓存如果存在，则删除
				this.registeredSingletons.add(beanName);
			}
		}
	}

AbstractAutowireCapableBeanFactory

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {

..............

if (hasInstAwareBpps) {
			if (pvs == null) {
				pvs = mbd.getPropertyValues();
			}
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) { // 如果@Autowired标注，走到AutowiredAnnotationBeanPostProcessor这个Processor 会进入到postProcessProperties方法
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; // 如果是AutowiredAnnotationBeanPostProcessor，下面会属性注入
					PropertyValues pvsToUse = ibp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName); // 这里会属性注入
					if (pvsToUse == null) { // 上面@Autowired注解 会调用AutowiredAnnotationBeanPostProcessor.postProcessProperties
						if (filteredPds == null) {
							filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
						}
						pvsToUse = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
						if (pvsToUse == null) {
							return;
						}
					}
					pvs = pvsToUse;
				}
			}
		}

..............

}

DefaultListableBeanFactory

public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {

		descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
		if (Optional.class == descriptor.getDependencyType()) {
			return createOptionalDependency(descriptor, requestingBeanName);
		}
		else if (ObjectFactory.class == descriptor.getDependencyType() ||
				ObjectProvider.class == descriptor.getDependencyType()) {
			return new DependencyObjectProvider(descriptor, requestingBeanName);
		}
		else if (javaxInjectProviderClass == descriptor.getDependencyType()) {
			return new Jsr330Factory().createDependencyProvider(descriptor, requestingBeanName);
		}
		else {
			Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(
					descriptor, requestingBeanName);
			if (result == null) {
				result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter); // 这里执行
			}
			return result;
		}
	}

public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {


.....................

     if (instanceCandidate instanceof Class) {
          instanceCandidate = descriptor.resolveCandidate(autowiredBeanName, type, this); // 这里A引用B  这里会先处理B的初始化 其实就是调用beanFactory.getBean(beanName);
     }

....................

}

 

AutowiredFieldElement

protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {

......................

    if (value != null) {
	    ReflectionUtils.makeAccessible(field);
	    field.set(bean, value);
	}

.....................


}

AutowiredMethodElement

protected void inject(Object bean, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {

...................

    if (arguments != null) {
        try {
		    ReflectionUtils.makeAccessible(method);
		    method.invoke(bean, arguments);
		}
		catch (InvocationTargetException ex) {
		    throw ex.getTargetException();
		}
    }

..................



}