java - 如何使用java为xml中的属性设置前缀

Question

我喜欢在使用 Java 创建 XML 文件时为属性设置前缀。我需要的结果是

<entry gd:etag="*">
    <id>Text</id>
</entry>

但我已经明白了

<entry etag="*">
    <id>Text</id>
</entry>

我写的代码是

DocumentBuilderFactory docBuildFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuildFactory.newDocumentBuilder();
Document doc = docBuilder.newDocument();
Element entry = doc.createElement("entry");
entry.setAttribute("etag","*");
doc.appendChild(entry);
Element id = doc.createElement("id");
id.setTextContent("Text");
entry.appendChild(id);
.....

我不知道如何设置属性的前缀。有人可以建议我如何做到这一点吗？

Answer 1

您需要将 DocumentBuilderFactory 设置为命名空间感知，并且需要设置该前缀的命名空间，并对具有 XML 命名空间的属性使用 setAttributeNS。

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class Entry {
    public static void main(String[] args)
            throws IOException, ParserConfigurationException, TransformerException {
        String ns = "http://schemas.google.com/g/2005"; // just a guess
        DocumentBuilderFactory docBuildFactory = DocumentBuilderFactory.newInstance();
        docBuildFactory.setNamespaceAware(true);
        DocumentBuilder docBuilder = docBuildFactory.newDocumentBuilder();
        Document doc = docBuilder.newDocument();
        Element entry = doc.createElement("entry");
        entry.setAttributeNS(ns, "gd:etag", "*");
        doc.appendChild(entry);
        Element id = doc.createElement("id");
        id.setTextContent("Text");
        entry.appendChild(id);
        printDocument(doc, System.out);
    }

    public static void printDocument(Document doc, OutputStream out)
            throws IOException, TransformerException {
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer = tf.newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
        transformer.setOutputProperty(OutputKeys.METHOD, "xml");
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");

        transformer.transform(new DOMSource(doc),
                new StreamResult(new OutputStreamWriter(out, "UTF-8")));
    }
}

输出:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<entry xmlns:gd="http://schemas.google.com/g/2005" gd:etag="*">
    <id>Text</id>
</entry>

将 namespace URN 替换为正确的 namespace URN；我只是根据 Google 搜索 gd:etag 前缀进行了猜测，该前缀显示了一些 Google Data API 和 Google Contacts API 内容。