解析 xml 为Document

清疚 2023-06-21 04:53 23阅读 0赞

**目录**

分析

问题：EntityResolver

DefaultDocumentLoader源码：

--------------------

# 分析 #

DefaultDocumentLoader\#loadDocument方法是标准的 SAX 解析xml文件的代码，没有什么特殊处理的地方。  
    1.创建DocumentBuilderFactory  
    2.根据 DocumentBuilderFactory 创建 DocumentBuilder  
    3.DocumentBuilder 解析 InputSource 为 Document

# 问题：[EntityResolver][] #

EntityResolver 解决 DTD 或XSD文件通过网络下载比较慢的问题，解决方案是本地获取 DTD或 XSD 文件。

# DefaultDocumentLoader源码： #

详细看代码中注释

package org.springframework.beans.factory.xml;
    
    import javax.xml.parsers.DocumentBuilder;
    import javax.xml.parsers.DocumentBuilderFactory;
    import javax.xml.parsers.ParserConfigurationException;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.lang.Nullable;
    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 {
        private static final String SCHEMA_LANGUAGE_ATTRIBUTE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage";
        private static final String XSD_SCHEMA_LANGUAGE = "http://www.w3.org/2001/XMLSchema";
        private static final Log logger = LogFactory.getLog(DefaultDocumentLoader.class);
    
        public DefaultDocumentLoader() {
        }
        /**
        * 这里是标准的 SAX 解析xml文件的代码，没有什么特殊处理的地方。
        * 1.创建DocumentBuilderFactory
        * 2.根据 DocumentBuilderFactory 创建 DocumentBuilder
        * 3.DocumentBuilder 解析 InputSource 为 Document
        *
        *
        */
        public Document loadDocument(InputSource inputSource, EntityResolver entityResolver, ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {
            // SAX, validationMode:2表示DTD，3表示XSD， 
            // namespaceAware 这里为false，表示是否可以处理命名空间，false为不可以
            DocumentBuilderFactory factory = this.createDocumentBuilderFactory(validationMode, namespaceAware);
            if(logger.isTraceEnabled()) {
                logger.trace("Using JAXP provider [" + factory.getClass().getName() + "]");
            }
            // 创建 DocumentBuilder
            DocumentBuilder builder = this.createDocumentBuilder(factory, entityResolver, errorHandler);
            // 解析xml文件，文件通过 ClassPathResource --> EncodedResource --> InputSource
            return builder.parse(inputSource);
        }
    
        protected DocumentBuilderFactory createDocumentBuilderFactory(int validationMode, boolean namespaceAware) throws ParserConfigurationException {
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            factory.setNamespaceAware(namespaceAware);
            if(validationMode != 0) {
                factory.setValidating(true);
                if(validationMode == 3) {
                    factory.setNamespaceAware(true);
    
                    try {
                        factory.setAttribute("http://java.sun.com/xml/jaxp/properties/schemaLanguage", "http://www.w3.org/2001/XMLSchema");
                    } catch (IllegalArgumentException var6) {
                        ParserConfigurationException pcex = new ParserConfigurationException("Unable to validate using XSD: Your JAXP provider [" + factory + "] does not support XML Schema. Are you running on Java 1.4 with Apache Crimson? Upgrade to Apache Xerces (or Java 1.5) for full XSD support.");
                        pcex.initCause(var6);
                        throw pcex;
                    }
                }
            }
    
            return factory;
        }
        /**
        * 1.创建 DocumentBuilder 
        * 2.配置 EntityResolver ，这是获取 DTD、XSD的方法，具体参考：https://blog.csdn.net/ruanhao1203/article/details/103489931
        */
        protected DocumentBuilder createDocumentBuilder(DocumentBuilderFactory factory, @Nullable EntityResolver entityResolver, @Nullable ErrorHandler errorHandler) throws ParserConfigurationException {
            DocumentBuilder docBuilder = factory.newDocumentBuilder();
            if(entityResolver != null) {
                docBuilder.setEntityResolver(entityResolver);
            }
    
            if(errorHandler != null) {
                docBuilder.setErrorHandler(errorHandler);
            }
    
            return docBuilder;
        }
    }

[EntityResolver]: https://blog.csdn.net/ruanhao1203/article/details/103489931