Spring源码学习--获取Document

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Spring在容器的基本实现流程中会涉及到关于xml文件操作，在这里跟踪一下源码，看一下spring在解析xml文件之前，对xml的Document是怎么获取的。

一、DefaultDocumentLoader

在Spring中XmlBeanFactoryReader类对于文档的读取并没有亲自去做加载，而是委托给DocumentLoader去执行，其中DocumentLoader只是个接口：

package org.springframework.beans.factory.xml;import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;public interface DocumentLoader {Document loadDocument(InputSource inputSource, EntityResolver entityResolver,ErrorHandler errorHandler, int validationMode, boolean namespaceAware)throws Exception;}

真正去做文档读取的实现类是DefaultDocumentLoader。

package org.springframework.beans.factory.xml;import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;import org.springframework.util.xml.XmlValidationModeDetector;
import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;public class DefaultDocumentLoader implements DocumentLoader {/*** JAXP attribute used to configure the schema language for validation.*/private static final String SCHEMA_LANGUAGE_ATTRIBUTE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage";/*** JAXP attribute value indicating the XSD schema language.*/private static final String XSD_SCHEMA_LANGUAGE = "http://www.w3.org/2001/XMLSchema";private static final Log logger = LogFactory.getLog(DefaultDocumentLoader.class);/*** Load the {@link Document} at the supplied {@link InputSource} using the standard JAXP-configured* XML parser.*/@Overridepublic Document loadDocument(InputSource inputSource, EntityResolver entityResolver,ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);if (logger.isDebugEnabled()) {logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");}DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);return builder