Spring中Bean注入源码示例解析

public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {
	void setScope(@Nullable String scope);
	@Nullable
	String getScope();
	void setLazyInit(boolean lazyInit);
	boolean isLazyInit();
}
//bean的原数据
public interface BeanMetadataElement {
	@Nullable
	Object getSource();
}

public interface BeanDefinitionRegistry extends AliasRegistry {
	void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException;
	void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
	BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
	boolean containsBeanDefinition(String beanName);
	String[] getBeanDefinitionNames();
	int getBeanDefinitionCount();
	boolean isBeanNameInUse(String beanName);
}

public class SimpleBeanDefinitionRegistry extends SimpleAliasRegistry implements BeanDefinitionRegistry {
	/**beanDefinition的容器，通过ConcurrentHashMap实现. */
	private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(64);
	//该类的实现方法只是实现了最简单的beanDefinition的注入，在Java开发环境中并不会使用该实现类
	@Override
	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException {
		Assert.hasText(beanName, "'beanName' must not be empty");
		Assert.notNull(beanDefinition, "BeanDefinition must not be null");
		this.beanDefinitionMap.put(beanName, beanDefinition);
	}
}

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
		//beanDefinition的容器
		private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
		//向BeanFactory中注入BeanDefinition
		public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {
			Assert.hasText(beanName, "Bean name must not be empty");
			Assert.notNull(beanDefinition, "BeanDefinition must not be null");
			if (beanDefinition instanceof AbstractBeanDefinition) {
				try {
					((AbstractBeanDefinition) beanDefinition).validate();
				}
				catch (BeanDefinitionValidationException ex) {
					throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
							"Validation of bean definition failed", ex);
				}
			}
			BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
			//判断beanDefinition容器中是否已存在该beanDefinition
			if (existingDefinition != null) {
				//是否可以覆盖
				if (!isAllowBeanDefinitionOverriding()) {
					throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
				} else if (existingDefinition.getRole() < beanDefinition.getRole()) {
					// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
					if (logger.isInfoEnabled()) {
						logger.info("Overriding user-defined bean definition for bean '" + beanName +
								"' with a framework-generated bean definition: replacing [" +
								existingDefinition + "] with [" + beanDefinition + "]");
					}
				} else if (!beanDefinition.equals(existingDefinition)) {
					if (logger.isDebugEnabled()) {
						logger.debug("Overriding bean definition for bean '" + beanName +
								"' with a different definition: replacing [" + existingDefinition +
								"] with [" + beanDefinition + "]");
					}
				} else {
					if (logger.isTraceEnabled()) {
						logger.trace("Overriding bean definition for bean '" + beanName +
								"' with an equivalent definition: replacing [" + existingDefinition +
								"] with [" + beanDefinition + "]");
					}
				}
				//覆盖beanDefinition
				this.beanDefinitionMap.put(beanName, beanDefinition);
			} else { //容器中不存在该beanDefinition的处理
				if (hasBeanCreationStarted()) {
					synchronized (this.beanDefinitionMap) { //对beanDefinition加锁
						//注入该beanDefinition
						this.beanDefinitionMap.put(beanName, beanDefinition);
						List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
						updatedDefinitions.addAll(this.beanDefinitionNames);
						updatedDefinitions.add(beanName);
						this.beanDefinitionNames = updatedDefinitions;
						if (this.manualSingletonNames.contains(beanName)) {
							Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
							updatedSingletons.remove(beanName);
							this.manualSingletonNames = updatedSingletons;
						}
					}
				}
				else {
					// Still in startup registration phase
					this.beanDefinitionMap.put(beanName, beanDefinition);
					this.beanDefinitionNames.add(beanName);
					this.manualSingletonNames.remove(beanName);
				}
				this.frozenBeanDefinitionNames = null;
			}
		if (existingDefinition != null || containsSingleton(beanName)) {
			resetBeanDefinition(beanName);
		}
	}
}

public interface SingletonBeanRegistry {
	//注入bean
	void registerSingleton(String beanName, Object singletonObject);
	//获取bean
	@Nullable
	Object getSingleton(String beanName);
	//是否存在bean
	boolean containsSingleton(String beanName);
	String[] getSingletonNames();
	int getSingletonCount();
	Object getSingletonMutex();
}

public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {
	//获取bean的方式平时使用ApplicationContext就是最终调用该方法
	public Object getBean(String name) throws BeansException {
		return doGetBean(name, null, null, false);
	}
	@Override
	public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
		return doGetBean(name, requiredType, null, false);
	}
	@Override
	public Object getBean(String name, Object... args) throws BeansException {
		return doGetBean(name, null, args, false);
	}
	public <T> T getBean(String name, @Nullable Class<T> requiredType, @Nullable Object... args)
			throws BeansException {
		return doGetBean(name, requiredType, args, false);
	}
	/**
	* 从容器中获取bean的主要逻辑
	*/
	protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
			@Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
		final String beanName = transformedBeanName(name);
		Object bean;
		// Eagerly check singleton cache for manually registered singletons.
		Object sharedInstance = getSingleton(beanName);
		if (sharedInstance != null && args == null) {
			if (logger.isTraceEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}
		else {
			//省略部分代码
			try {
				//先获取beanDefinition
				final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
				checkMergedBeanDefinition(mbd, beanName, args);
				// Guarantee initialization of beans that the current bean depends on.
				String[] dependsOn = mbd.getDependsOn();
				if (dependsOn != null) {
					for (String dep : dependsOn) {
						if (isDependent(beanName, dep)) {
							throw new BeanCreationException(mbd.getResourceDescription(), beanName,
									"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
						}
						registerDependentBean(dep, beanName);
						try {
							getBean(dep);
						}
						catch (NoSuchBeanDefinitionException ex) {
							throw new BeanCreationException(mbd.getResourceDescription(), beanName,
									"'" + beanName + "' depends on missing bean '" + dep + "'", ex);
						}
					}
				}
				// 单例模式下获取bean的方式
				if (mbd.isSingleton()) {
					sharedInstance = getSingleton(beanName, () -> {
						try {
							return createBean(beanName, mbd, args);
						}
						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);
				}
				else if (mbd.isPrototype()) {//原型模式下的bean的获取
					// It's a prototype -> create a new instance.
					Object prototypeInstance = null;
					try {
						beforePrototypeCreation(beanName);
						//原型模式每次都需要创建bean
						prototypeInstance = createBean(beanName, mbd, args);
					}
					finally {
						afterPrototypeCreation(beanName);
					}
					bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
				}
				else { 
					String scopeName = mbd.getScope();
					final Scope scope = this.scopes.get(scopeName);
					if (scope == null) {
						throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
					}
					try {
						Object scopedInstance = scope.get(beanName, () -> {
							beforePrototypeCreation(beanName);
							try {
								return createBean(beanName, mbd, args);
							}
							finally {
								afterPrototypeCreation(beanName);
							}
						});
						bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
					}
					catch (IllegalStateException ex) {
						throw new BeanCreationException(beanName,
								"Scope '" + scopeName + "' is not active for the current thread; consider " +
								"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
								ex);
					}
				}
			}
			catch (BeansException ex) {
				cleanupAfterBeanCreationFailure(beanName);
				throw ex;
			}
		}
		//省略部分代码
		return (T) bean;
	}
	//将实现beanPostProcessor的实现类加入到链表中用于对bean的前置或者后置处理
	@Override
	public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
		Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
		// Remove from old position, if any
		this.beanPostProcessors.remove(beanPostProcessor);
		// Track whether it is instantiation/destruction aware
		if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
			this.hasInstantiationAwareBeanPostProcessors = true;
		}
		if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
			this.hasDestructionAwareBeanPostProcessors = true;
		}
		// Add to end of list
		this.beanPostProcessors.add(beanPostProcessor);
	}
	//销毁bean的方法
	@Override
	public void destroyBean(String beanName, Object beanInstance) {
		destroyBean(beanName, beanInstance, getMergedLocalBeanDefinition(beanName));
	}
	protected void destroyBean(String beanName, Object bean, RootBeanDefinition mbd) {
		new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), getAccessControlContext()).destroy();
	}
}

public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
	//单例bean的容器，开发过程中获取的bean都是从该容器中获取的：即所谓的一级缓存
	private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
	//单例bean的beanFactory的容器：即所谓的三级缓存
	private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
	//提前初始化的bean的容器，该容器的bean并没有任何属性值只是提前将bean注入到该容器中用于后续的判断
	//即所谓的二级缓存
	private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);
	//已注册的单例bean的beanName列表
	private final Set<String> registeredSingletons = new LinkedHashSet<>(256);
	//注入bean的方法
	public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
		Assert.notNull(beanName, "Bean name must not be null");
		Assert.notNull(singletonObject, "Singleton object must not be null");
		synchronized (this.singletonObjects) {
			Object oldObject = this.singletonObjects.get(beanName);
			if (oldObject != null) {
				throw new IllegalStateException("Could not register object [" + singletonObject +
												"] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
			}
			addSingleton(beanName, singletonObject);
		}
	}
	/**
	* 将bean注入容器中，操作四个容器主要用于bean的循环依赖问题
	*/
	protected void addSingleton(String beanName, Object singletonObject) {
		synchronized (this.singletonObjects) {
			this.singletonObjects.put(beanName, singletonObject);
			this.singletonFactories.remove(beanName);
			this.earlySingletonObjects.remove(beanName);
			this.registeredSingletons.add(beanName);
		}
	}
}