在Java 8中美化XML

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在Java 8中美化XML

我有一个已存储为DOM文档的XML文件，并且我想将其漂亮地打印到控制台上，最好不使用外部库。我知道这个问题在这个网站上已经多次被问及，但是以前的回答都没有对我起作用。我正在使用java 8，因此这可能是我的代码与以前提出的问题不同的地方。我还尝试通过从网络上找到的代码手动设置转换器，但这只会导致一个not found错误。

这是我的代码，当前仅将每个xml元素输出为控制台左侧的新行。

import java.io.*;
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
public class Test {
    public Test(){
        try {
            //java.lang.System.setProperty("javax.xml.transform.TransformerFactory", "org.apache.xalan.xsltc.trax.TransformerFactoryImpl");
            DocumentBuilderFactory dbFactory;
            DocumentBuilder dBuilder;
            Document original = null;
            try {
                dbFactory = DocumentBuilderFactory.newInstance();
                dBuilder = dbFactory.newDocumentBuilder();
                original = dBuilder.parse(new InputSource(new InputStreamReader(new FileInputStream("xml Store - Copy.xml"))));
            } catch (SAXException | IOException | ParserConfigurationException e) {
                e.printStackTrace();
            }
            StringWriter stringWriter = new StringWriter();
            StreamResult xmlOutput = new StreamResult(stringWriter);
            TransformerFactory tf = TransformerFactory.newInstance();
            //tf.setAttribute("indent-number", 2);
            Transformer transformer = tf.newTransformer();
            transformer.setOutputProperty(OutputKeys.METHOD, "xml");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
            transformer.transform(new DOMSource(original), xmlOutput);
            java.lang.System.out.println(xmlOutput.getWriter().toString());
        } catch (Exception ex) {
            throw new RuntimeException("Error converting to String", ex);
        }
    }
    public static void main(String[] args){
        new Test();
    }
}

admin 更改状态以发布 2023年5月23日
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2 答案

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我猜问题与原始文件中的空文本节点（即仅包含空格的文本节点）有关。你应该尝试在解析后立即使用以下代码程序化地将它们移除。如果不移除它们，Transformer将会保留它们。

original.getDocumentElement().normalize();
XPathExpression xpath = XPathFactory.newInstance().newXPath().compile("//text()[normalize-space(.) = '']");
NodeList blankTextNodes = (NodeList) xpath.evaluate(original, XPathConstants.NODESET);
for (int i = 0; i < blankTextNodes.getLength(); i++) {
     blankTextNodes.item(i).getParentNode().removeChild(blankTextNodes.item(i));
}

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0 Comments

针对Espinosa的评论，这里提供了一个解决方案，适用于“原始xml文件没有缩进或不包含换行符”的情况。

背景

下面是本解决方案的灵感来源文章（参见下面的参考资料）的节选：

根据DOM规范，标签外的空格是完全有效的，并且它们会被正确地保留。要删除它们，我们可以使用XPath的normalize-space函数来定位所有空白节点并首先将它们删除。

Java代码

public static String toPrettyString(String xml, int indent) {
    try {
        // Turn xml string into a document
        Document document = DocumentBuilderFactory.newInstance()
                .newDocumentBuilder()
                .parse(new InputSource(new ByteArrayInputStream(xml.getBytes("utf-8"))));
        // Remove whitespaces outside tags
        document.normalize();
        XPath xPath = XPathFactory.newInstance().newXPath();
        NodeList nodeList = (NodeList) xPath.evaluate("//text()[normalize-space()='']",
                                                      document,
                                                      XPathConstants.NODESET);
        for (int i = 0; i < nodeList.getLength(); ++i) {
            Node node = nodeList.item(i);
            node.getParentNode().removeChild(node);
        }
        // Setup pretty print options
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        transformerFactory.setAttribute("indent-number", indent);
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        // Return pretty print xml string
        StringWriter stringWriter = new StringWriter();
        transformer.transform(new DOMSource(document), new StreamResult(stringWriter));
        return stringWriter.toString();
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}

示例用法

String xml = "" + //
             "\n   "  + //
             "\nCoco Puff" + //
             "\n        10    ";
System.out.println(toPrettyString(xml, 4));

输出结果


    Coco Puff
    10

参考资料

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