Add new attributes to an existing XML node in java?

Question

I want to add an attribute to an existing xml node.I don't want to add new elements (new nodes) to my xml file, I just want to add a new attribute. How can I do this?

In particular I've tried this lines of code:

Element process = doc.getElementsById("id");
    process.setAttribute("modelgroup", "");

TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new  File("C:\\Users\\Blerta\\workspaceKEPLER\\XML_to_JSON\\SampleExample.xml"));
transformer.transform(source, result);

But I get the following exception:

Exception in thread "main" java.lang.NullPointerException
    at Main.appendAttributes(Main.java:172)
    at Main.displayNodes(Main.java:65)
    at Main.displayNodes(Main.java:138)
    at Main.main(Main.java:42)**

paste the line where nullpointer occures

Łukasz Rzeszotarski
– Łukasz Rzeszotarski

2013-11-18 16:50:39 +00:00
Commented Nov 18, 2013 at 16:50 — Łukasz Rzeszotarski
– Łukasz Rzeszotarski, Commented Nov 18, 2013 at 16:50

payam_sbr · Accepted Answer · 2017-05-12 07:29:32Z

31

in DOM parser it is very easy. get your node and simply use this function.

((Element)node).setAttribute("attr_name","attr_value");

then finally update your document. like this..

        Transformer transformer = TransformerFactory.newInstance().newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(OutputKeys.METHOD, "xml");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "5");
        DOMSource source = new DOMSource(document);
        StreamResult result = new StreamResult(new File(tablePath));
        transformer.transform(source, result);

edited May 12, 2017 at 7:29

payam_sbr

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answered Nov 18, 2013 at 16:37

subash

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3 Comments

user2966458 Over a year ago

I've allready tried this but I cannot apply setAttribute to the node

subash Over a year ago

doc.getElementsByTagName("process"); it is return NodeList. try like this. NodeList list = doc.getElementsByTagName("process");. Element el = (Element)list.item(0); then you can use el.setAttribute("attr_name","attr_val");

Stephan Over a year ago

What if node isn't castable to Element?

Sergey Tarasov · Accepted Answer · 2014-12-10 03:06:11Z

8

The easiest and the shortest is to cast the node to org.w3c.dom.Element and then invoke setAttribute on it:

((Element)aNode).setAttribute("name", "value");

answered Dec 10, 2014 at 3:06

Sergey Tarasov

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5 Comments

Stephan Over a year ago

What if node isn't castable to Element?

Renat Gatin Over a year ago

Yes, what if aNode does not extend Element class?

Dawood ibn Kareem Over a year ago

@Stephan, it doesn't make sense to add an attribute to something that isn't an Element.

Stephan Over a year ago

@DawoodibnKareem An exception will be raised if aNode isn't castable to Element.

Dawood ibn Kareem Over a year ago

Well, yes, obviously. That's exactly what SHOULD happen, because adding an attribute to something that's not an Element makes no sense.

stripybadger · Accepted Answer · 2013-11-18 16:46:33Z

3

You could do it in a few lines using xslt. Oracle have a half decent tutorial with all the code snippets http://docs.oracle.com/javase/tutorial/jaxp/xslt/transformingXML.html

The key bit for your xslt would be something like the following:

    <xsl:template match="elementToAddNewAttrTo">
        <xsl:attribute name="newAttrName">NewAttrValue</xsl:attribute>
    </xsl:template>

answered Nov 18, 2013 at 16:46

stripybadger

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Comments

Yeti · Accepted Answer · 2017-08-13 20:48:23Z

1

Recommended approach:

Node node = ...;
if(node.getNodeType() == Node.ELEMENT_NODE)
{
    ((Element) node).setAttribute("name", "value");
}

Situational approach:

try
{
    // ...
    Node node = ...;
    ((Element) node).setAttribute("name", "value");
    // ...
}
catch(ClassCastException e)
{
    // Handle exception
}

Only use the try-catch approach if you already know that all the nodes that you process should be of type 'Element' (and thus any other case is an "exception" and should break from the code).

answered Aug 13, 2017 at 20:48

Yeti

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