在 XML 文件的特定位置插入字符串

Question

我有一个 XML 文件 (client_23.xml)，如下所示。我有一个字符串变量out，我需要在XML 下方插入一个特定位置。这不是我的完整 XML，因为我有很多其他嵌套的东西，函数标签将在其中，并且不一致，因为这个 XML 是通过代码生成的，所以我需要

<?xml version="1.0"?>
<clients>
    <!-- some other code here -->

    <function>
    </function>

    <function>
    </function>

    <function>
        <name>data_values</name>
        <variables>
            <variable>
            <name>temp</name>
            <type>double</type>
            </variable>
        </variables>
        <block>
            <opster>temp = 1</opster>   
        </block>
    </function>
</clients>

我需要解析上面的XML，找到一个名为data_values的函数，然后在<block>标签中插入out字符串变量。这不是我的完整 XML，因为我有很多其他嵌套的东西，函数标签将在其中，并且它不一致，因为这个 XML 是通过代码生成的，所以我需要解析和迭代并找到它，然后放它。

所以最终的 xml 将如下所示：

<?xml version="1.0"?>
<clients>
    <!-- some other code here -->

    <function>
    </function>

    <function>
    </function>

    <function>
        <name>data_values</name>
        <variables>
            <variable>
            <name>temp</name>
            <type>double</type>
            </variable>
        </variables>
        <block>
            <!-- new stuff added and old things were gone -->
            <opster>hello = world</opster>
            <opster>abc = def</opster>
        </block>
    </function>
</clients>

以下是我得到的代码，但我无法理解如何在块标记中的data_values 函数中放入变量。

StringBuilder out = new StringBuilder();
// some data in out variable, properly formatted with new lines.

String location = key.getPathName();
String clientIdPath = location + "/" + "client_23.xml";
File fileName = new File(clientIdPath);

DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
Document document = documentBuilder.parse(fileName);

NodeList dataValueFunction = document.getElementsByTagName("function");
// I have started iterating but I am not able to understand how to insert "out"
// variable inside block
for (int i = 0; i < dataValueFunction.getLength(); i++) {
    Node node = dataValueFunction.item(i);
    System.out.println(node.getNodeName());
    NodeList childList = node.getChildNodes();
    for (int j = 0; j < childList.getLength(); j++) {
        Node node1 = childList.item(j);
        if (node1 != null && node1.getNodeName().equalsIgnoreCase("name")
                        && node1.getTextContent().equalsIgnoreCase("data_values")) {
            // now what should I do here?
        }
    }
}

Answer 1

检查这个问题。您可以使用 XPath 表达式来定位正确的函数标记并使用 Xpath 对其进行更新。

How to update XML using XPath and Java

这是一个快速代码。

public static void main(String[] args) {
    try {
        FileInputStream file = new FileInputStream(new File("data.xml"));
        List<String> outs = Arrays.asList(new String[] { "hello = world", "abc = def" });
        DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = builderFactory.newDocumentBuilder();

        Document xmlDocument = builder.parse(file);

        XPath xPath = XPathFactory.newInstance().newXPath();

        System.out.println("*************************");
        String expression = "//clients/function/name[text()='data_values']";
        System.out.println(expression);
        Node nameTag = (Node) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODE);

        for (int i = 0; i < nameTag.getParentNode().getChildNodes().getLength(); i++) {
            if (nameTag.getParentNode().getChildNodes().item(i).getNodeName().equals("block")) {
                System.out.println("GOT BLOCK");
                nameTag.getParentNode().removeChild(nameTag.getParentNode().getChildNodes().item(i));
                Node node = xmlDocument.createElement("block");



                nameTag.getParentNode().appendChild(node);
                for (String out : outs) {
                    Node newNode = xmlDocument.createElement("opster");
                    newNode.setTextContent(out);

                    node.appendChild(newNode);
                }

            }
        }
        TransformerFactory tFactory = TransformerFactory.newInstance();
        Transformer transformer = tFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
        DOMSource source = new DOMSource(xmlDocument);
        StreamResult result = new StreamResult(System.out);
        transformer.transform(source, result);

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (SAXException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ParserConfigurationException e) {
        e.printStackTrace();
    } catch (XPathExpressionException e) {
        e.printStackTrace();
    } catch (TransformerConfigurationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (TransformerException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Answer 2

已编辑：将“out”的值添加到先前存在的“block”元素

按照@user489732 的建议，使用XPath 本地化节点，然后使用您的值创建一个新节点，然后将其插入到函数元素中。不过我会使用不同的方法：

public static void main(String[] args) throws ParserConfigurationException, IOException, SAXException, XPathExpressionException, TransformerException {

    // Your initial input
    String myXML = "<?xml version=\"1.0\"?>\n" +
            "<clients>\n" +
            "    <!-- some other code here -->\n" +
            "\n" +
            "    <function>\n" +
            "    </function>\n" +
            "\n" +
            "    <function>\n" +
            "    </function>\n" +
            "\n" +
            "    <function>\n" +
            "        <name>data_values</name>\n" +
            "        <variables>\n" +
            "            <variable>\n" +
            "            <name>temp</name>\n" +
            "            <type>double</type>\n" +
            "            </variable>\n" +
            "        </variables>\n" +
            "        <block>\n" +
            "            <!-- new stuff added and old things were gone -->\n" +
            "            <opster>hello = world</opster>\n" +
            "            <opster>abc = def</opster>\n" +
            "        </block>\n" +
            "    </function>\n" +
            "</clients>";

    // you will have to create an input stream from your XML file,
    // in this case I'm using a ByteArrayInputStream, you'll probably
    // need a FileInputStream
    InputStream myXMLStream = new ByteArrayInputStream(myXML.getBytes(Charset.forName("UTF-8")));

    String out = "My value whatever it is";

    // Create xpath expression
    XPathFactory xPathfactory = XPathFactory.newInstance();
    XPath xpath = xPathfactory.newXPath();
    XPathExpression expr = xpath.compile("/clients/function/block[../name/text() = 'data_values']");

    // Load document
    DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
    Document document = documentBuilder.parse(myXMLStream);

    // Search for the node
    NodeList blockList = (NodeList) expr.evaluate(document, XPathConstants.NODESET);
    Element blockElement = (Element)blockList.item(0);

    // Insert your value inside element "block"
    // CAVEAT: if the value of "out" contains "tags" (xml elements)
    // then "createTextNode" won't work, you need to create elements
    // with the different methods of "document" (document.createXXXX())
    Node textNode = document.createTextNode(out);
    blockElement.insertBefore(textNode, blockElement.getFirstChild());

    // Write the document to its final destination
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(document);

    // instead of System.out, use a more appropriate stream:
     StreamResult result = new StreamResult(System.out);

    transformer.transform(source, result);
}

Answer 3

如果有人认为目前提供的答案太复杂，这里还有一个，vtd-xml...这里是why vtd-xml is much better than DOM

import com.ximpleware.*;

public class replaceContent {
    public static void main(String[] s) throws VTDException, Exception{
        VTDGen vg = new VTDGen();
        AutoPilot ap = new AutoPilot();
        XMLModifier xm = new XMLModifier();
        if (vg.parseFile("d:\\xml\\input2.xml", true)){
            VTDNav vn = vg.getNav();
            ap.bind(vn);
            xm.bind(vn);
            ap.selectXPath("/clients/function/block");
            int i=-1;
            byte[] s1 = ("\r\n\t\t<opster>hello = world</opster>\r\n\t\t"+
                        "<opster>abc = def</opster>\r\n\t").getBytes();
            while((i=ap.evalXPath())!=-1){
                xm.insertAfterHead(s1);
                long l= vn.getContentFragment(); // add new stuff after the starting tag
                xm.removeContent((int)l, (int)(l>>32)); // remove old stuff
            }
            xm.output("d:\\xml\\new.xml");
        }
        }
}