Spring容器-优快云博客

本文链接：https://blog.youkuaiyun.com/xwf1228/article/details/90713312

博客围绕Spring的XmlBeanFactory容器创建展开。先给出测试代码并展示时序图，清晰呈现其逻辑顺序。接着解析xmlbeanFactory，Spring通过XmlBeanDefinitionReader加载资源，该读取器加载xml文件内容主要做两件事：将资源文件转成document，注册文档中的bean。

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XmlBeanFactory容器创建

测试代码

//省略get/set
public class MyTestBean {
    private String testStr = "testStr";
}
//配置
<bean id="myTestBean" scope="singleton" class="com.bean.MyTestBean" >
    <property name="testStr" value="haha" />
</bean>
//这里先把classpath下的资源文件读取到resource
 Resource resource = new ClassPathResource("beanFactoryTest.xml");
 //容器的创建
 BeanFactory beanFactory = new XmlBeanFactory(resource);
 MyTestBean myTestBean = (MyTestBean) beanFactory.getBean("myTestBean");

先看时序图

时序图中对xmlbeanFactory的逻辑顺序一目了然
xmlbeanFactory解析

public class XmlBeanFactory extends DefaultListableBeanFactory {

	private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);

	public XmlBeanFactory(Resource resource) throws BeansException {
		this(resource, null);
	}

	public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
		super(parentBeanFactory);
		this.reader.loadBeanDefinitions(resource);
	}
	
}

这里spring定义了一个XmlBeanDefinitionReader 来加载资源，继续跟进代码

public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
	return loadBeanDefinitions(new EncodedResource(resource));
}

public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
		Assert.notNull(encodedResource, "EncodedResource must not be null");
		if (logger.isInfoEnabled()) {
			logger.info("Loading XML bean definitions from " + encodedResource.getResource());
		}

		Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
		if (currentResources == null) {
			currentResources = new HashSet<EncodedResource>(4);
			this.resourcesCurrentlyBeingLoaded.set(currentResources);
		}
		if (!currentResources.add(encodedResource)) {
			throw new BeanDefinitionStoreException(
					"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
		}
		try {
			InputStream inputStream = encodedResource.getResource().getInputStream();
			try {
				InputSource inputSource = new InputSource(inputStream);
				if (encodedResource.getEncoding() != null) {
					inputSource.setEncoding(encodedResource.getEncoding());
				}
				return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
			}
			finally {
				inputStream.close();
			}
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(
					"IOException parsing XML document from " + encodedResource.getResource(), ex);
		}
		finally {
			currentResources.remove(encodedResource);
			if (currentResources.isEmpty()) {
				this.resourcesCurrentlyBeingLoaded.remove();
			}
		}
	}

这里比较啰嗦，其实就一句话
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
其他都是处理编码，IO，以及一些异常的东西，继续

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
			throws BeanDefinitionStoreException {
		try {
			Document doc = doLoadDocument(inputSource, resource);
			return registerBeanDefinitions(doc, resource);
		}catch(){
			//异常部分省略了
		}
	}

到这里我们大致就清楚了，其实 XmlBeanDefinitionReader 加载xml文件中的内容就做了两件事
1.读取资源文件转换成 document
2.注册文档中的bean，也就是xml配置文件中的bean