JAVA modifying XML file

Question

I'm trying to modify my Config.xml file from JAVA program, file contains data about MySql connection.

Here's the code after button click:

        DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
        File f = new File("Config.xml");
        Document doc = domFactory.newDocumentBuilder().parse(f.getAbsolutePath());

        String url = server_field.getText();
        String user = db_login_field.getText();
        String pass = db_pass_field.getText();
        String baze = db_name_field.getText();

        klases.update_xml(doc, "jdbc/url", url);
        klases.update_xml(doc, "jdbc/username", user);
        klases.update_xml(doc, "jdbc/password", pass);
        klases.update_xml(doc, "jdbc/name", baze);

        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer tf = transformerFactory.newTransformer();
        DOMSource domSource = new DOMSource(doc);
        try (FileOutputStream fos = new FileOutputStream(f)) {
             StreamResult sr = new StreamResult(fos);
             tf.transform(domSource, sr);
        }

update_xml function:

public static void update_xml(Document doc, String path, String def) {
    String p[] = path.split("/");
    //search nodes or create them if they do not exist
    Node n = doc;
    for (int i = 0; i < p.length; i++) {
        NodeList kids = n.getChildNodes();
        Node nfound = null;
        for (int j = 0; j < kids.getLength(); j++) {
            if (kids.item(j).getNodeName().equals(p[i])) {
                nfound = kids.item(j);
                break;
            }
        }
        if (nfound == null) {
            nfound = doc.createElement(p[i]);  // LINE 300
            n.appendChild(nfound);
            n.appendChild(doc.createTextNode("\n")); //add whitespace, so the result looks nicer. Not really needed
        }
        n = nfound;
    }
    NodeList kids = n.getChildNodes();
    for (int i = 0; i < kids.getLength(); i++) {
        if (kids.item(i).getNodeType() == Node.TEXT_NODE) {
            //text node exists
            kids.item(i).setNodeValue(def); //override
            return;
        }
    }

    n.appendChild(doc.createTextNode(def));

}

And here is XML file:

<?xml version="1.0" encoding="UTF-8"?>
<jdbc>
    <url>localhost:3306</url>
    <driver>com.mysql.jdbc.Driver</driver>
    <username>username</username>
    <password>password</password>
    <name>database</name>
</jdbc>

And here's the error:

Exception in thread "AWT-EventQueue-0" org.w3c.dom.DOMException: INVALID_CHARACTER_ERR: An invalid or illegal XML character is specified. 
at com.sun.org.apache.xerces.internal.dom.CoreDocumentImpl.createElement(CoreDocumentImpl.java:622)
at programa.klases.update_xml(klases.java:300)

Line 300 commented. Waiting for soliution, thank you!

A [space] character is been generted in your `p` array because of the leading `/` character in the path — MadProgrammer, Aug 05 '15 at 06:00
Now I didn't get any error, but didn't get any changes in file too. — Rytis, Aug 05 '15 at 06:03
Your example code doesn't seem to save anything - but it works okay for me — MadProgrammer, Aug 05 '15 at 06:06

score 1 · Accepted Answer · answered Aug 05 '15 at 06:13

A [space] character is been generted in your p array because of the leading / character in the path

You can remove the / from the original path...

update_xml(doc, "jdbc/url", url);
update_xml(doc, "jdbc/username", user);
update_xml(doc, "jdbc/password", pass);
update_xml(doc, "jdbc/name", baze);

which will get rid of the immediate error

Now I didn't get any error, but didn't get any changes in file too.

None of you example code shows you actually saving the Document back to the file, once loaded, there is no association between the DOM and the source it come from, you need to save the contents yourself, for example...

DOMSource domSource = new DOMSource(doc);
try (FileOutputStream fos = new FileOutputStream(f)) {
    StreamResult sr = new StreamResult(fos);
    tf.transform(domSource, sr);
}

Use the save functionality AFTER you've finished updating the DOM (so under all the `update_xml` calles. And it works fine for me — MadProgrammer, Aug 05 '15 at 06:25

JAVA modifying XML file

1 Answers1