Spring源码解析3 IOC容器的初始化

上一次我们了解BeanDefinition的在载入和解析，现在我们来看一下BeanDefinition的注册过程：

当BeanDefinition在IoC容器中载入和解析完成后，用户定义的BeanDefinition信息已经在IoC容器内建立起了自己的数据结构以及相应的数据表示，在Default

ListableBeanFactory中通过一个HashMap来持有载入的BeanDefinition。

DefaultBeanDefinitionDocumentReader

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();

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protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
/*按照Spring的Bean规则解析得到的了BeanDefinition的封装类BeanDefinitionHolder后,调用BeanDefinitionReaderUtils.registerBeanDefinition()方法注册BeanDefinition*/
		BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
		if (bdHolder != null) {
			bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
			try {
				// Register the final decorated instance.
				BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
			}
			catch (BeanDefinitionStoreException ex) {
				getReaderContext().error("Failed to register bean definition with name '" +
						bdHolder.getBeanName() + "'", ele, ex);
			}
			// Send registration event.
			getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
		}
	}

 

BeanDefinitionReaderUtils：

 

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public static void registerBeanDefinition(
			BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
			throws BeanDefinitionStoreException {

		// Register bean definition under primary name.
		String beanName = definitionHolder.getBeanName();
//真正的BeanDefinition的注册在这里,它调用DefaultListableBeanFactory
//下的registerBeanDefinition完成了注册
		registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

		// Register aliases for bean name, if any.
		String[] aliases = definitionHolder.getAliases();
		if (aliases != null) {
			for (String aliase : aliases) {
				registry.registerAlias(beanName, aliase);
			}
		}
	}

 

DefaultListableBeanFactory:

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);
			}
		}

		synchronized (this.beanDefinitionMap) {
			Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
			if (oldBeanDefinition != null) {
				if (!this.allowBeanDefinitionOverriding) {
					throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
							"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
							"': There is already [" + oldBeanDefinition + "] bound.");
				}
				else {
					if (this.logger.isInfoEnabled()) {
						this.logger.info("Overriding bean definition for bean '" + beanName +
								"': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
					}
				}
			}
			else {
				this.beanDefinitionNames.add(beanName);
				this.frozenBeanDefinitionNames = null;
			}
			this.beanDefinitionMap.put(beanName, beanDefinition);

			resetBeanDefinition(beanName);
		}
	}

 

这是正常的注册过程，把Bean的名字存入到BeanDefinitionNames的同时，将beanName作为Map的key,把beanDefinition作为value存入到IoC容器持有的beanDefinitionMap中去。完成了BeanDefinition的注册，就完成了IoC容器的初始化过程。现在我们就可以这些BeanDefinition了。

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