Spring源码：XMLBeanDefinitionReader

目录

1、概述

2、初始化

3、解析Spring配置

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1、概述

XMLBeanDefinitionReader 是 XmlBeanFactory 中特殊的存在，利用 SAX 方式解析Spring配置XML文件为 Document 的辅助类。

2、初始化

package org.springframework.beans.factory.xml;

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {

// 初始化
    public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
// AbstractBeanDefinitionReader 初始化 BeanDefinitionRegistry、ResourceLoader、Environment
        super(registry);
// SAX解析异常类
        this.errorHandler = new SimpleSaxErrorHandler(this.logger);
// 验证XML是DTD、XSD 的类
        this.validationModeDetector = new XmlValidationModeDetector();
// 存放 Resource的 ThreadLocal
        this.resourcesCurrentlyBeingLoaded = new NamedThreadLocal("XML bean definition resources currently being loaded");
    }

}

3、解析Spring配置

package org.springframework.beans.factory.xml;

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {

    public void setValidating(boolean validating) {
        this.validationMode = validating ? 1 : 0;
        this.namespaceAware = !validating;
    }

    public void setValidationModeName(String validationModeName) {
        this.setValidationMode(constants.asNumber(validationModeName).intValue());
    }

    public void setValidationMode(int validationMode) {
        this.validationMode = validationMode;
    }

    public int getValidationMode() {
        return this.validationMode;
    }

    public void setNamespaceAware(boolean namespaceAware) {
        this.namespaceAware = namespaceAware;
    }

    public boolean isNamespaceAware() {
        return this.namespaceAware;
    }

    public void setProblemReporter(@Nullable ProblemReporter problemReporter) {
        this.problemReporter = (ProblemReporter)(problemReporter != null ? problemReporter : new FailFastProblemReporter());
    }

    public void setEventListener(@Nullable ReaderEventListener eventListener) {
        this.eventListener = (ReaderEventListener)(eventListener != null ? eventListener : new EmptyReaderEventListener());
    }

    public void setSourceExtractor(@Nullable SourceExtractor sourceExtractor) {
        this.sourceExtractor = (SourceExtractor)(sourceExtractor != null ? sourceExtractor : new NullSourceExtractor());
    }

    public void setNamespaceHandlerResolver(@Nullable NamespaceHandlerResolver namespaceHandlerResolver) {
        this.namespaceHandlerResolver = namespaceHandlerResolver;
    }

    public void setDocumentLoader(@Nullable DocumentLoader documentLoader) {
        this.documentLoader = (DocumentLoader)(documentLoader != null ? documentLoader : new DefaultDocumentLoader());
    }

    public void setEntityResolver(@Nullable EntityResolver entityResolver) {
        this.entityResolver = entityResolver;
    }

    protected EntityResolver getEntityResolver() {
        if (this.entityResolver == null) {
            ResourceLoader resourceLoader = this.getResourceLoader();
            if (resourceLoader != null) {
                this.entityResolver = new ResourceEntityResolver(resourceLoader);
            } else {
                this.entityResolver = new DelegatingEntityResolver(this.getBeanClassLoader());
            }
        }

        return this.entityResolver;
    }

    public void setErrorHandler(ErrorHandler errorHandler) {
        this.errorHandler = errorHandler;
    }

    public void setDocumentReaderClass(Class documentReaderClass) {
        this.documentReaderClass = documentReaderClass;
    }

// 加载Resource
    public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
// 包装成 EncodedResource，可以根据配置的编码类型解析 Spring配置文件
        return this.loadBeanDefinitions(new EncodedResource(resource));
    }

// 加载Resource
    public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
        Assert.notNull(encodedResource, "EncodedResource must not be null");
        if (this.logger.isInfoEnabled()) {
            this.logger.info("Loading XML bean definitions from " + encodedResource.getResource());
        }
// 判断该线程内是否已经存在 Resource
        Set currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get();
        if (currentResources == null) {
            currentResources = new HashSet(4);
            this.resourcesCurrentlyBeingLoaded.set(currentResources);
        }

        if (!((Set)currentResources).add(encodedResource)) {
            throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");
        } else {
            int var5;
            try {
// 获取配置文件流
                InputStream inputStream = encodedResource.getResource().getInputStream();

                try {
// SAX解析 start
                    InputSource inputSource = new InputSource(inputStream);
                    if (encodedResource.getEncoding() != null) {
                        inputSource.setEncoding(encodedResource.getEncoding());
                    }
// 正式解析配置文件流
                    var5 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource());
                } finally {
                    inputStream.close();
                }
            } catch (IOException var15) {
                throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15);
            } finally {
                ((Set)currentResources).remove(encodedResource);
                if (((Set)currentResources).isEmpty()) {
                    this.resourcesCurrentlyBeingLoaded.remove();
                }

            }

            return var5;
        }
    }

    public int loadBeanDefinitions(InputSource inputSource) throws BeanDefinitionStoreException {
        return this.loadBeanDefinitions(inputSource, "resource loaded through SAX InputSource");
    }

    public int loadBeanDefinitions(InputSource inputSource, @Nullable String resourceDescription) throws BeanDefinitionStoreException {
        return this.doLoadBeanDefinitions(inputSource, new DescriptiveResource(resourceDescription));
    }

// 正式解析
    protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource) throws BeanDefinitionStoreException {
        try {
// 转换成 Document
            Document doc = this.doLoadDocument(inputSource, resource);
// 
            return this.registerBeanDefinitions(doc, resource);
        } catch (BeanDefinitionStoreException var4) {
            throw var4;
        } catch (SAXParseException var5) {
            throw new XmlBeanDefinitionStoreException(resource.getDescription(), "Line " + var5.getLineNumber() + " in XML document from " + resource + " is invalid", var5);
        } catch (SAXException var6) {
            throw new XmlBeanDefinitionStoreException(resource.getDescription(), "XML document from " + resource + " is invalid", var6);
        } catch (ParserConfigurationException var7) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "Parser configuration exception parsing XML from " + resource, var7);
        } catch (IOException var8) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "IOException parsing XML document from " + resource, var8);
        } catch (Throwable var9) {
            throw new BeanDefinitionStoreException(resource.getDescription(), "Unexpected exception parsing XML document from " + resource, var9);
        }
    }

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

    protected int getValidationModeForResource(Resource resource) {
        int validationModeToUse = this.getValidationMode();
        if (validationModeToUse != 1) {
            return validationModeToUse;
        } else {
            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 {
                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);
            }
        }
    }

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

    protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
        return (BeanDefinitionDocumentReader)BeanDefinitionDocumentReader.class.cast(BeanUtils.instantiateClass(this.documentReaderClass));
    }

    public XmlReaderContext createReaderContext(Resource resource) {
        return new XmlReaderContext(resource, this.problemReporter, this.eventListener, this.sourceExtractor, this, this.getNamespaceHandlerResolver());
    }

    public NamespaceHandlerResolver getNamespaceHandlerResolver() {
        if (this.namespaceHandlerResolver == null) {
            this.namespaceHandlerResolver = this.createDefaultNamespaceHandlerResolver();
        }

        return this.namespaceHandlerResolver;
    }

    protected NamespaceHandlerResolver createDefaultNamespaceHandlerResolver() {
        ClassLoader cl = this.getResourceLoader() != null ? this.getResourceLoader().getClassLoader() : this.getBeanClassLoader();
        return new DefaultNamespaceHandlerResolver(cl);
    }
}