小夫的笔记

但行好事 莫问前程

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容器的基本实现

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package com.example.demo;



import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

public class Main {
  public static void main(String[] args) throws Exception {

    BeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource("Beans.xml"));

        beanFactory.getBean("myTestBean");
   }

}

Resource

org.springframework.core.io.Resource
是对不同类型资源的封装 大体上想要拿到的就是那个资源的Inputstrem

XmlBeanFactory

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

加载Bean

检查Bean 是不是已经被加载过了 如果没有就委托给XmlBeanDefinitionReader#doLoadBeanDefinitions进行实际类型的加载
XmlBeanDefinitionReader#loadBeanDefinitions

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public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
		Assert.notNull(encodedResource, "EncodedResource must not be null");
		if (logger.isTraceEnabled()) {
			logger.trace("Loading XML bean definitions from " + encodedResource);
		}
		// resource 这个已经被reader load过了
		Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
		if (currentResources == null) {
			currentResources = new HashSet<>(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()) {
			InputSource inputSource = new InputSource(inputStream);
			if (encodedResource.getEncoding() != null) {
				inputSource.setEncoding(encodedResource.getEncoding());
			}
			return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(
					"IOException parsing XML document from " + encodedResource.getResource(), ex);
		}
		finally {
			currentResources.remove(encodedResource);
			if (currentResources.isEmpty()) {
				this.resourcesCurrentlyBeingLoaded.remove();
			}
		}
	}

实际加载BeanDefinitions

XmlBeanDefinitionReader#doLoadBeanDefinitions

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protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
			throws BeanDefinitionStoreException {

		try {
      // 解析xml 得到Document 
			Document doc = doLoadDocument(inputSource, resource);
			int count = registerBeanDefinitions(doc, resource);
			if (logger.isDebugEnabled()) {
				logger.debug("Loaded " + count + " bean definitions from " + resource);
			}
			return count;
		}
		catch (BeanDefinitionStoreException ex) {
			throw ex;
		}
		catch (SAXParseException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
		}
		catch (SAXException ex) {
			throw new XmlBeanDefinitionStoreException(resource.getDescription(),
					"XML document from " + resource + " is invalid", ex);
		}
		catch (ParserConfigurationException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Parser configuration exception parsing XML from " + resource, ex);
		}
		catch (IOException ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"IOException parsing XML document from " + resource, ex);
		}
		catch (Throwable ex) {
			throw new BeanDefinitionStoreException(resource.getDescription(),
					"Unexpected exception parsing XML document from " + resource, ex);
		}
	}

解析Xml 获得Docuemnt对象

XmlBeanDefinitionReader#doLoadDocument

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protected Document doLoadDocument(InputSource inputSource, Resource resource) throws Exception {
	return this.documentLoader.loadDocument(inputSource, getEntityResolver(), this.errorHandler,
			getValidationModeForResource(resource), isNamespaceAware());
}

获取Resource的验证方式

xml的验证方式主要有DTD和XSD
读取每一行，如果行内有DOCTYPE 表示验证的方式是DTD 否则是XSD
XmlValidationModeDetector#detectValidationMode

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/**
 * Detect the validation mode for the XML document in the supplied {@link InputStream}.
 * Note that the supplied {@link InputStream} is closed by this method before returning.
 * @param inputStream the InputStream to parse
 * @throws IOException in case of I/O failure
 * @see #VALIDATION_DTD
 * @see #VALIDATION_XSD
 */
public int detectValidationMode(InputStream inputStream) throws IOException {
	// Peek into the file to look for DOCTYPE.
	BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
	try {
		boolean isDtdValidated = false;
		String content;
		while ((content = reader.readLine()) != null) {
			content = consumeCommentTokens(content);
			if (this.inComment || !StringUtils.hasText(content)) {
				continue;
			}
			if (hasDoctype(content)) {
				isDtdValidated = true;
				break;
			}
			if (hasOpeningTag(content)) {
				// End of meaningful data...
				break;
			}
		}
		return (isDtdValidated ? VALIDATION_DTD : VALIDATION_XSD);
	}
	catch (CharConversionException ex) {
		// Choked on some character encoding...
		// Leave the decision up to the caller.
		return VALIDATION_AUTO;
	}
	finally {
		reader.close();
	}
}

设定解析Document的 DocumentBuilderFactory 和 DocumentBuilder

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public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
		ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {

	DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
	if (logger.isTraceEnabled()) {
		logger.trace("Using JAXP provider [" + factory.getClass().getName() + "]");
	}
	DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
	return builder.parse(inputSource);
}

解析和注册BeanDefinitons

DefaultBeanDefinitionDocumentReader#registerBeanDefinitions

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public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
		BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
		int countBefore = getRegistry().getBeanDefinitionCount();
		documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
		return getRegistry().getBeanDefinitionCount() - countBefore;
	}

解析Xml中的Beans

DefaultBeanDefinitionDocumentReader#doRegisterBeanDefinitions

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@SuppressWarnings("deprecation")  // for Environment.acceptsProfiles(String...)
protected void doRegisterBeanDefinitions(Element root) {
	// Any nested <beans> elements will cause recursion in this method. In
	// order to propagate and preserve <beans> default-* attributes correctly,
	// keep track of the current (parent) delegate, which may be null. Create
	// the new (child) delegate with a reference to the parent for fallback purposes,
	// then ultimately reset this.delegate back to its original (parent) reference.
	// this behavior emulates a stack of delegates without actually necessitating one.
	BeanDefinitionParserDelegate parent = this.delegate;
	this.delegate = createDelegate(getReaderContext(), root, parent);

	if (this.delegate.isDefaultNamespace(root)) {
		String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
		if (StringUtils.hasText(profileSpec)) {
			String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
					profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
			// We cannot use Profiles.of(...) since profile expressions are not supported
			// in XML config. See SPR-12458 for details.
			if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
				if (logger.isDebugEnabled()) {
					logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec +
							"] not matching: " + getReaderContext().getResource());
				}
				return;
			}
		}
	}

	preProcessXml(root);
	parseBeanDefinitions(root, this.delegate);
	postProcessXml(root);

	this.delegate = parent;
}

解析Beans 标签的attribute元素

Reader 中会生成ParserDelegate
DefaultBeanDefinitionDocumentReader#createDelegate

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protected BeanDefinitionParserDelegate createDelegate(
      XmlReaderContext readerContext, Element root, @Nullable BeanDefinitionParserDelegate parentDelegate) {

   BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
   delegate.initDefaults(root, parentDelegate);
   return delegate;
}

BeanDefinitionParserDelegate#initDefaults

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public void initDefaults(Element root, @Nullable BeanDefinitionParserDelegate parent) {
		populateDefaults(this.defaults, (parent != null ? parent.defaults : null), root);
		this.readerContext.fireDefaultsRegistered(this.defaults);
	}

BeanDefinitionParserDelegate#populateDefaults

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protected void populateDefaults(DocumentDefaultsDefinition defaults, @Nullable DocumentDefaultsDefinition parentDefaults, Element root) {
	String lazyInit = root.getAttribute(DEFAULT_LAZY_INIT_ATTRIBUTE);
	if (isDefaultValue(lazyInit)) {
		// Potentially inherited from outer <beans> sections, otherwise falling back to false.
		lazyInit = (parentDefaults != null ? parentDefaults.getLazyInit() : FALSE_VALUE);
	}
	defaults.setLazyInit(lazyInit);

	String merge = root.getAttribute(DEFAULT_MERGE_ATTRIBUTE);
	if (isDefaultValue(merge)) {
		// Potentially inherited from outer <beans> sections, otherwise falling back to false.
		merge = (parentDefaults != null ? parentDefaults.getMerge() : FALSE_VALUE);
	}
	defaults.setMerge(merge);

	String autowire = root.getAttribute(DEFAULT_AUTOWIRE_ATTRIBUTE);
	if (isDefaultValue(autowire)) {
		// Potentially inherited from outer <beans> sections, otherwise falling back to 'no'.
		autowire = (parentDefaults != null ? parentDefaults.getAutowire() : AUTOWIRE_NO_VALUE);
	}
	defaults.setAutowire(autowire);

	if (root.hasAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE)) {
		defaults.setAutowireCandidates(root.getAttribute(DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE));
	}
	else if (parentDefaults != null) {
		defaults.setAutowireCandidates(parentDefaults.getAutowireCandidates());
	}

	if (root.hasAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE)) {
		defaults.setInitMethod(root.getAttribute(DEFAULT_INIT_METHOD_ATTRIBUTE));
	}
	else if (parentDefaults != null) {
		defaults.setInitMethod(parentDefaults.getInitMethod());
	}

	if (root.hasAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE)) {
		defaults.setDestroyMethod(root.getAttribute(DEFAULT_DESTROY_METHOD_ATTRIBUTE));
	}
	else if (parentDefaults != null) {
		defaults.setDestroyMethod(parentDefaults.getDestroyMethod());
	}

	defaults.setSource(this.readerContext.extractSource(root));
}