Java xml自闭标签

Question

My Java program looks like:

public static void main(String[] args) {
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    DocumentBuilder db;
    try {
        db = dbf.newDocumentBuilder();
        Document document = db.parse(new ByteArrayInputStream("<test><test1></test1></test>".getBytes("UTF-8")));
        StringWriter stringWriter = new StringWriter();
        Transformer transformer = TransformerFactory.newInstance().newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
        transformer.setOutputProperty(OutputKeys.INDENT, "no");
        transformer.setOutputProperty(OutputKeys.STANDALONE, "yes");
        transformer.transform(new DOMSource(document), new StreamResult(stringWriter));
        System.out.println(stringWriter.toString());
    } catch (ParserConfigurationException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (TransformerConfigurationException e) {
        e.printStackTrace();
    } catch (TransformerException e) {
        e.printStackTrace();
    } catch (SAXException e) {
        e.printStackTrace();
    }
}

Output is: <test><test1/></test> I want output <test><test1></test1></test> .

Because I'm using JasperReports and html style only allow my wanted output. How to achieve that? Is there any output property of Transformer or any property of DocumentBuilderFactory to do wanted output?

Answer 1

如果在调用transformer.transform之前添加此行 - 输出将采用html样式：

transformer.setOutputProperty(OutputKeys.METHOD, "html");

Answer 2

A way to make Java's Transformer write full closing tags is to make little changes to the Document. In my case, I build the DOM myself (instead of parsing an XML from String). For each node of which I know it will make a self-closing tag, I have to (unfortunately) add a textNode with some random content of which you know it will certainly not occur in the content itself. This is what I do for elements to which I don't add any other child (and thus would become a self-closing tag):

DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.newDocument();
Element test = doc.createElement("test");
doc.appendChild(root);
Element element = doc.createElement("test1");
element.appendChild("_plchldr_"); // because we know it doesn't have children

In case of an existing Document, you would have to traverse it to find elements that don't have children. Add these same placeholders to them.

Later, when streaming this XML to our Writer, these placeholders have to be removed from the generated XML:

TransformerFactory factory = TransformerFactory.newInstance();
transformer.setOutputProperty("omit-xml-declaration", "yes");
StringWriter sw = new StringWriter();
StreamResult result = new StreamResult(sw);
DOMSource source = new DOMSource(doc);
transformer.transform(source, result);
// and here's the trick:
System.out.println( sw.toString().replaceAll("_plchldr_", "") );

Alternatively you could use a wrapping Writer that removes "_plchldr_" streaming. Considered the size of my XMLs (<4KB) I didn't bother writing one.

Another alternative, if you don't want to go with replacing text from the output, you could add a comment instead of a text node:

element.appendChild(doc.createComment(" "));

The result doesn't need those place holders to be removed to be valid XML, however, you will have pointless comments in your output.

I consider this as a dirty workaround, but it least it works!