How to find and replace an attribute value in a XML

Question

I am building a \"XML scanner\" in Java that finds attribute values starting with \"!Here:\". The attribute value contains instructions to replace later. for example I hav

Answer 1

In order to modify some element or attribute values in the XML file, while still being respectful of XML structure, you will need to use a XML parser. It's a bit more involved than just String$replace()...

Given an example XML like:

In order to change the 2 markers !Here, you need

1. to load the file into a dom Document,
2. select with xpath the wanted nodes. Here I search for all nodes in the document with an attribute value that contains the string !Here. The xpath expression is //*[contains(@value, '!Here')].

3. do the transformation you want on each selected nodes. Here I just change !Here by What?.

4. save the modified dom Document into a new file.

---

static String inputFile = "./beans.xml";
static String outputFile = "./beans_new.xml";

// 1- Build the doc from the XML file
Document doc = DocumentBuilderFactory.newInstance()
            .newDocumentBuilder().parse(new InputSource(inputFile));

// 2- Locate the node(s) with xpath
XPath xpath = XPathFactory.newInstance().newXPath();
NodeList nodes = (NodeList)xpath.evaluate("//*[contains(@value, '!Here')]",
                                          doc, XPathConstants.NODESET);

// 3- Make the change on the selected nodes
for (int idx = 0; idx < nodes.getLength(); idx++) {
    Node value = nodes.item(idx).getAttributes().getNamedItem("value");
    String val = value.getNodeValue();
    value.setNodeValue(val.replaceAll("!Here", "What?"));
}

// 4- Save the result to a new XML doc
Transformer xformer = TransformerFactory.newInstance().newTransformer();
xformer.transform(new DOMSource(doc), new StreamResult(new File(outputFile)));

The resulting XML file is: