Java读取 XML 文件并将 XML 字符串打印到控制台或者将 XML 写入文件 示例

Java从文件中读取 XML

将 XML 从 .xml文件读取到 Document对象的示例。

private static Document convertXMLFileToXMLDocument(String filePath) 
{
	//Parser that produces DOM object trees from XML content
	DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

	//API to obtain DOM Document instance
	DocumentBuilder builder = null;
	try 
	{
		//Create DocumentBuilder with default configuration
		builder = factory.newDocumentBuilder();

		//Parse the content to Document object
		Document xmlDocument = builder.parse(new File(filePath));

		return xmlDocument;
	} 
	catch (Exception e) 
	{
		e.printStackTrace();
	}
	return null;
}

将 XML 转换为字符串

要将 XML 对象例如：org.w3c.dom.Document转换为字符串，我们需要以下类：

• javax.xml.transform.Transformer：这个类的一个实例可以使用它的 transform()方法将源树转换为结果树。
• javax.xml.transform.TransformerFactory：创建 Transformer实例的工厂。
• javax.xml.transform.dom.DOMSource：文档对象模型（DOM）树形式的源树。
• javax.xml.transform.stream.StreamResult：转换结果树的持有者，可以是 XML、纯文本、HTML 或者某种其他形式的标记。

将 XML 打印到控制台或者日志文件

private static void writeXmlDocumentToXmlFile(Document xmlDocument)
{
	TransformerFactory tf = TransformerFactory.newInstance();
    Transformer transformer;
    try {
        transformer = tf.newTransformer();

        // Uncomment if you do not require XML declaration
        // transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

        //A character stream that collects its output in a string buffer, 
        //which can then be used to construct a string.
        StringWriter writer = new StringWriter();
        //transform document to string 
        transformer.transform(new DOMSource(xmlDocument), new StreamResult(writer));
        String xmlString = writer.getBuffer().toString();	
        System.out.println(xmlString);						//Print to console or logs
    } 
    catch (TransformerException e) 
    {
        e.printStackTrace();
    }
    catch (Exception e) 
    {
        e.printStackTrace();
    }
}

将 XML 写入文件

private static void writeXmlDocumentToXmlFile(Document xmlDocument, String fileName)
{
	TransformerFactory tf = TransformerFactory.newInstance();
    Transformer transformer;
    try {
        transformer = tf.newTransformer();

        //Uncomment if you do not require XML declaration
        //transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");

        //Write XML to file
        FileOutputStream outStream = new FileOutputStream(new File(fileName)); 
        transformer.transform(new DOMSource(xmlDocument), new StreamResult(outStream));
    } 
    catch (TransformerException e) 
    {
        e.printStackTrace();
    }
    catch (Exception e) 
    {
        e.printStackTrace();
    }
}