如何在序列化之前从一个dom中去掉仅空白的文本节点?

您可以使用xpath查找空文本节点,然后以编程方式删除它们,如下所示:

XPathFactory xpathFactory = XPathFactory.newInstance();
// XPath to find empty text nodes.
XPathExpression xpathExp = xpathFactory.newXPath().compile(
        "//text()[normalize-space(.) = '']");  
NodeList emptyTextNodes = (NodeList) 
        xpathExp.evaluate(doc, XPathConstants.NODESET);

// Remove each empty text node from document.
for (int i = 0; i < emptyTextNodes.getLength(); i++) {
    Node emptyTextNode = emptyTextNodes.item(i);
    emptyTextNode.getParentNode().removeChild(emptyTextNode);
}

如果您想要比XSL模板更容易实现的对节点删除的控制,这种方法可能会很有用。

尝试使用以下XSL和 strip-space 要序列化DOM的元素:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="xml" omit-xml-declaration="yes"/>

  <xsl:strip-space elements="*"/>

  <xsl:template match="@*|node()">
    <xsl:copy>
     <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>

</xsl:stylesheet>

http://helpdesk.objects.com.au/java/how-do-i-remove-whitespace-from-an-xml-document

下面的代码删除注释节点和带有所有空格的文本节点。如果文本节点具有某个值,则将修剪该值。

public static void clean(Node node)
{
  NodeList childNodes = node.getChildNodes();

  for (int n = childNodes.getLength() - 1; n >= 0; n--)
  {
     Node child = childNodes.item(n);
     short nodeType = child.getNodeType();

     if (nodeType == Node.ELEMENT_NODE)
        clean(child);
     else if (nodeType == Node.TEXT_NODE)
     {
        String trimmedNodeVal = child.getNodeValue().trim();
        if (trimmedNodeVal.length() == 0)
           node.removeChild(child);
        else
           child.setNodeValue(trimmedNodeVal);
     }
     else if (nodeType == Node.COMMENT_NODE)
        node.removeChild(child);
  }
}

裁判: http://www.sitepoint.com/removing-useless-nodes-from-the-dom/

另一种可能的方法是在删除目标节点的同时删除相邻的空白:

private void removeNodeAndTrailingWhitespace(Node node) {
    List<Node> exiles = new ArrayList<Node>();

    exiles.add(node);
    for (Node whitespace = node.getNextSibling();
            whitespace != null && whitespace.getNodeType() == Node.TEXT_NODE && whitespace.getTextContent().matches("\\s*");
            whitespace = whitespace.getNextSibling()) {
        exiles.add(whitespace);
    }

    for (Node exile: exiles) {
        exile.getParentNode().removeChild(exile);
    }
}

这样做的好处是保持现有格式的其余部分不变。

以下代码有效:

public String getSoapXmlFormatted(String pXml) {
    try {
        if (pXml != null) {
            DocumentBuilderFactory tDbFactory = DocumentBuilderFactory
                    .newInstance();
            DocumentBuilder tDBuilder;
            tDBuilder = tDbFactory.newDocumentBuilder();
            Document tDoc = tDBuilder.parse(new InputSource(
                    new StringReader(pXml)));
            removeWhitespaces(tDoc);
            final DOMImplementationRegistry tRegistry = DOMImplementationRegistry
                    .newInstance();
            final DOMImplementationLS tImpl = (DOMImplementationLS) tRegistry
                    .getDOMImplementation("LS");
            final LSSerializer tWriter = tImpl.createLSSerializer();
            tWriter.getDomConfig().setParameter("format-pretty-print",
                    Boolean.FALSE);
            tWriter.getDomConfig().setParameter(
                    "element-content-whitespace", Boolean.TRUE);
            pXml = tWriter.writeToString(tDoc);
        }
    } catch (RuntimeException | ParserConfigurationException | SAXException
            | IOException | ClassNotFoundException | InstantiationException
            | IllegalAccessException tE) {
        tE.printStackTrace();
    }
    return pXml;
}

public void removeWhitespaces(Node pRootNode) {
    if (pRootNode != null) {
        NodeList tList = pRootNode.getChildNodes();
        if (tList != null && tList.getLength() > 0) {
            ArrayList<Node> tRemoveNodeList = new ArrayList<Node>();
            for (int i = 0; i < tList.getLength(); i++) {
                Node tChildNode = tList.item(i);
                if (tChildNode.getNodeType() == Node.TEXT_NODE) {
                    if (tChildNode.getTextContent() == null
                            || "".equals(tChildNode.getTextContent().trim()))
                        tRemoveNodeList.add(tChildNode);
                } else
                    removeWhitespaces(tChildNode);
            }
            for (Node tRemoveNode : tRemoveNodeList) {
                pRootNode.removeChild(tRemoveNode);
            }
        }
    }
}

transformer.setOutputProperty(OutputKeys.INDENT, "yes");

这将保留XML缩进。