Java Remove empty XML tags

Question

I\'m looking for a simple Java snippet to remove empty tags from a (any) XML structure

    bla
    <         


        

Answer 1

If the xml is feed as a String; regex could be used to filter out empty elements:

<(\\w+)></\\1>|<\\w+/>

This will find empty elements.

data.replaceAll(re, "")

data in this case a variable holding your xml string.
Not saying this would be the best of solutions, but it is possible...

Answer 2

To remove all empty tags, even if they are one after another, one possibile solution is:

 private void removeEmptyTags(Document document) {
    List<Node> listNode = new ArrayList<Node>();
    findListEmptyTags(document.getRootElement(), listNode);
    if (listNode.size() == 0)
        return;

    for (Node node : listNode) {
        node.getParent().removeChild(node);
    }
    removeEmptyTags(document);
}

private void findListEmptyTags(Node node, List<Node> listNode) {

    if (node != null && node.getChildCount() == 0 && "".equals(node.getValue()) && ((Element) node).getAttributeCount() == 0) {
        listNode.add(node);
        return;
    }
    // recurse the children
    for (int i = 0; i < node.getChildCount(); i++) {
        findListEmptyTags(node.getChild(i), listNode);
    }
}

Answer 3

public static void main(String[] args) {

    final String regex1 = "<([a-zA-Z0-9-\\_]*)[^>]*/>";
    final String regex2 = "<([a-zA-Z0-9-\\_]*)[^>]*>\\s*</\\1>";

    String xmlString = "<xml><field1>bla</field1><field2></field2><field3/><structure1><field4><field50><field50/></field50></field4><field5></field5></structure1></xml>";
    System.out.println(xmlString);

    final Pattern pattern1 = Pattern.compile(regex1);
    final Pattern pattern2 = Pattern.compile(regex2);

    Matcher matcher1;
    Matcher matcher2;
    do { 
        xmlString = xmlString.replaceAll(regex1, "").replaceAll(regex2, "");
        matcher1 = pattern1.matcher(xmlString);
        matcher2 = pattern2.matcher(xmlString);
    } while (matcher1.find() || matcher2.find());

    System.out.println(xmlString);
}

Console:

<xml>
    <field1>bla</field1>
    <field2></field2>
    <field3/>
    <structure1>
        <field4>
            <field50>
                <field60/>
            </field50>
        </field4>
        <field5></field5>
    </structure1>
</xml>

<xml>
    <field1>bla</field1>
</xml>

Online demo here