Spring源码学习笔记1

Posted 2020-11-02 sonofthesea

1.Spring中最核心的两个类

1)DefaultListableBeanFactory

　　XmlBeanFactory继承自DefaultListableBeanFactory，DefaultListableBeanFactory是整个bean加载的核心部分，是Spring加载及注册bean的默认实现

2)XmlBeanDefinitionReader

2.示例代码

BeanFactory bf=new XmlBeanFactory(new ClassPathResource("beanFactoryTest.xml"));

XmlBeanFactory.class
public class XmlBeanFactory extends DefaultListableBeanFactory {
    private final XmlBeanDefinitionReader reader;

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

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

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

public int loadBeanDefinitions(EncodedResource encodedResource){
....　　
　　InputSource inputSource = new InputSource(inputStream);//通过SAX方式解析XML文件
....
　　this.doLoadBeanDefinitions(inputSource, encodedResource.getResource());

}

3.配置文件的封装

Resource implements InputStreamResource

 

4.AbstractAutowireCapableBeanFactory.ignoreDependencyInterface()

忽略给定接口的自动装配功能

5.加载Bean

protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException {
        try {
            int validationMode = this.getValidationModeForResource(resource);//获取xml文件的验证模式
            Document doc = this.documentLoader.loadDocument(inputSource, this.getEntityResolver(), this.errorHandler, validationMode, this.isNamespaceAware());//加载XML文件
            return this.registerBeanDefinitions(doc, resource);//返回注册bean的信息
        } catch (BeanDefinitionStoreException var5) {
            throw var5;
        } catch (SAXParseException var6) {
            throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + var6.getLineNumber() + " in XML document from " + resource + " is invalid", var6);
        } catch (SAXException var7) {
            throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", var7);
        } catch (ParserConfigurationException var8) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, var8);
        } catch (IOException var9) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, var9);
        } catch (Throwable var10) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, var10);
        }
    }

1)获取xml文件的验证模式

getValidationModeForResource(resource);

protected int getValidationModeForResource(Resource resource) {
    int validationModeToUse = this.getValidationMode();
    if (validationModeToUse != 1) {
        return validationModeToUse;
    } else {
　　　　　　//如果没有设定模式则进行自动检测模式
        int detectedMode = this.detectValidationMode(resource);
        return detectedMode != 1 ? detectedMode : 3;
    }
}

protected int detectValidationMode(Resource resource) {
        if (resource.isOpen()) {
            throw new BeanDefinitionStoreException("Passed-in Resource [" + resource + "] contains an open stream: " + "cannot determine validation mode automatically. Either pass in a Resource " + "that is able to create fresh streams, or explicitly specify the validationMode " + "on your XmlBeanDefinitionReader instance.");
        } else {
            InputStream inputStream;
            try {
                inputStream = resource.getInputStream();
            } catch (IOException var5) {
                throw new BeanDefinitionStoreException("Unable to determine validation mode for [" + resource + "]: cannot open InputStream. " + "Did you attempt to load directly from a SAX InputSource without specifying the " + "validationMode on your XmlBeanDefinitionReader instance?", var5);
            }

            try {
　　　　　　　　　　//将自动检测模式委托给了XmlValidationModeDetector类
　　　　　　　　　　　return this.validationModeDetector.detectValidationMode(inputStream); 
　　　　　　　} catch (IOException var4) { 
　　　　　　　　　　throw new BeanDefinitionStoreException("Unable to determine validation mode for [" + resource + "]: an error occurred whilst reading from the InputStream.", var4); 
　　　　　　　} 
　　　　　} 
　　}

 

2)加载XML文件，并得到对应的Document

委托给DocumentLoader类

EntityResolver的用法

EntityResolver的作用是项目本身就可以提供一个如何寻找DTD声明的方法，即由程序来实现寻找DTD声明的过程，比如我们将DTD文件放到项目中某处，在实现时直接将此文档读取并返回给SAX即可。这样就避免了通过网络来寻找相应的声明。

验证文件默认的加载方式是通过URL进行网络下载获取，这样会造成延迟，用户体验也不好，一般的做法都是将验证文件放在自己的工程里。

public interface EntityResolver {
    public abstract InputSource resolveEntity (String publicId,
                                               String systemId)
        throws SAXException, IOException;

}

3)返回注册bean的信息

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
　　　　　　//单一职责原则
        BeanDefinitionDocumentReader documentReader = this.createBeanDefinitionDocumentReader();
        documentReader.setEnvironment(this.getEnvironment());
        int countBefore = this.getRegistry().getBeanDefinitionCount();
　　　　　　//加载及注册bean
        documentReader.registerBeanDefinitions(doc, this.createReaderContext(resource));
        return this.getRegistry().getBeanDefinitionCount() - countBefore;
    }

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
        this.readerContext = readerContext;
        this.logger.debug("Loading bean definitions");
        Element root = doc.getDocumentElement();
        this.doRegisterBeanDefinitions(root);
    }

解析并注册BeanDefinitions
protected void doRegisterBeanDefinitions(Element root) {
        String profileSpec = root.getAttribute("profile");
        if (StringUtils.hasText(profileSpec)) {
            Assert.state(this.environment != null, "Environment must be set for evaluating profiles");
            String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, ",; ");
            if (!this.environment.acceptsProfiles(specifiedProfiles)) {
                return;
            }
        }

        BeanDefinitionParserDelegate parent = this.delegate;
        this.delegate = this.createHelper(this.readerContext, root, parent);
        this.preProcessXml(root);//模板方法模式
        this.parseBeanDefinitions(root, this.delegate);
        this.postProcessXml(root);
        this.delegate = parent;
    }

 

protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
        if (delegate.isDefaultNamespace(root)) {
            NodeList nl = root.getChildNodes();

            for(int i = 0; i < nl.getLength(); ++i) {
                Node node = nl.item(i);
                if (node instanceof Element) {
                    Element ele = (Element)node;
                    if (delegate.isDefaultNamespace(ele)) {
                        this.parseDefaultElement(ele, delegate);//处理默认Bean声明
                    } else {
                        delegate.parseCustomElement(ele);//处理自定义Bean声明
                    }
                }
            }
        } else {
            delegate.parseCustomElement(root);
        }
    }