XML文件和DOM Document、String字符串三种类型之间的相互转换

　　　　最近在工作中用到了解析XML文件，网上的教程一言难尽，分享一个我自己解析XML文件的方法，记录一下。有XML文件转成DOM，XML文件转成Sting，String转DOM等各种操作。用的包是 org.w3c.dom.Document下的

/**
 * @Author dengzp
 * @Date 2022/3/22
 * @Version 1.0
 * @Description
 */

public class OperateXMLByDOM {
    /**
     * 将给定文件的内容或者给定 URI 的内容解析为一个 XML 文档，并且返回一个新的 DOM Document 对象
     *
     * @param filePath 文件所在路径
     * @return DOM的Document对象
     * @throws Exception
     */
    public static Document xml2Doc(String filePath) {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = null;
        FileInputStream inputStream = null;
        Document doc = null;
        try {
            builder = factory.newDocumentBuilder();

            /* 通过文件方式读取,注意文件保存的编码和文件的声明编码要一致(默认文件声明是UTF-8) */
            File file = new File(filePath);
            doc = builder.parse(file);

            /* 通过一个URL方式读取 */
            URI uri = new URI(filePath);
            doc = builder.parse(uri.toString());

            /* 通过java IO 流的读取 */
            inputStream = new FileInputStream(filePath);
            doc = builder.parse(inputStream);
            return doc;
        } catch (Exception e) {
            return null;
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    return null;
                }
            }
        }
    }

    /**
     * Document 转换为 String 并且进行了格式化缩进
     *
     * @param doc XML的Document对象
     * @return String
     */
    public static String doc2FormatString(Document doc) {
        StringWriter stringWriter = null;
        try {
            stringWriter = new StringWriter();
            if (doc != null) {
                OutputFormat format = new OutputFormat(doc, "UTF-8", true);
                //format.setIndenting(true);//设置是否缩进，默认为true
                //format.setIndent(4);//设置缩进字符数
                //format.setPreserveSpace(false);//设置是否保持原来的格式,默认为 false
                //format.setLineWidth(500);//设置行宽度
                XMLSerializer serializer = new XMLSerializer(stringWriter, format);
                serializer.asDOMSerializer();
                serializer.serialize(doc);
                return stringWriter.toString();
            } else {
                return null;
            }
        } catch (Exception e) {
            return null;
        } finally {
            if (stringWriter != null) {
                try {
                    stringWriter.close();
                } catch (IOException e) {
                    return null;
                }
            }
        }
    }

    /**
     * Document 转换为 String
     *
     * @param doc XML的Document对象
     * @return String
     */
    public static String doc2String(Document doc) {
        try {
            Source source = new DOMSource(doc);
            StringWriter stringWriter = new StringWriter();
            Result result = new StreamResult(stringWriter);
            TransformerFactory factory = TransformerFactory.newInstance();
            Transformer transformer = factory.newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.transform(source, result);
            return stringWriter.getBuffer().toString();
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * String 转换为 Document 对象
     *
     * @param xml 字符串
     * @return Document 对象
     */
    public static Document string2Doc(String xml) {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = null;
        Document doc = null;
        InputSource source = null;
        StringReader reader = null;
        try {
            builder = factory.newDocumentBuilder();
            reader = new StringReader(xml);
            source = new InputSource(reader);//使用字符流创建新的输入源
            doc = builder.parse(source);
            return doc;
        } catch (Exception e) {
            return null;
        } finally {
            if (reader != null) {
                reader.close();
            }
        }
    }

    /**
     * Document 保存为 XML 文件
     *
     * @param doc  Document对象
     * @param path 文件路径
     */
    public static void doc2XML(Document doc, String path) {
        try {
            Source source = new DOMSource(doc);
            Result result = new StreamResult(new File(path));
            Transformer transformer = TransformerFactory.newInstance().newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.transform(source, result);
        } catch (Exception e) {
            return;
        }
    }

    public static void main(String[] args) {
        Document doc = xml2Doc("/Users/dengzhaoping/Desktop/license.xml");
        System.out.println("aa" + doc);
        System.out.println("bb" + doc2String(doc));
        System.out.println("cc" + doc2FormatString(doc));
        doc = string2Doc(doc2FormatString(doc));
        doc2XML(doc, "1.xml");
    }