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How to change a value in a XML-File?

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Moritz
Moritz on 2 Oct 2013
Commented: Robert Ungi on 3 Jan 2022
Hello,
i have this XML-code
<busStop id="BusStop0" lane="1to2_0" startPos="20" endPos="30"/>
<busStop id="BusStop1" lane="1to2_0" startPos="70" endPos="80"/>
<chargingStation id="ChrgStn1" lane="1to2_0" startPos="20" endPos="30" chrgPower="220"/>
I want to change the value in "chargingStation" for "startPos" and for "endPos".
How do i write in MatLab?
Thanks!!!

Answers (1)

Alessandro
Alessandro on 2 Oct 2013
Edited: Alessandro on 2 Oct 2013
If I understand you right and you use the java node structure for matlab than you could use this function to replace the node:
%Function to replace a w3c node
function xmlreplacenode(node1,nodenew)
parent = node1.getParentNode;
node1.getParentNode.removeChild(xmlnode);%Delete the node
parent.appendChild(nodenew);
If not you should first parse the document with:
xDoc = xmlread(handles.tmpverzeichn);
You still need a function to generate a new node from a string maybe. For that you can try this:
%input doc is java org.w3c.dom Document
%str is a xml string
function node = parsestr2node(doc,str)
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.w3c.dom.Node;
import java.io.*;
inStream = org.xml.sax.InputSource();
inStream.setCharacterStream(java.io.StringReader(str));
docBuilderFactory = DocumentBuilderFactory.newInstance();
docBuilder = docBuilderFactory.newDocumentBuilder();
tmpdoc = docBuilder.parse (inStream);
node = doc.importNode(tmpdoc.getChildNodes.item(0),true);
If it doesn t work maybe you need some java files
  4 Comments
Heinke W
Heinke W on 4 Nov 2021
Edited: Heinke W on 4 Nov 2021
Hi Alessandro,
first of all I want to say thank you for your reply. I got a similar issue. I have to admit to be noob, especially when it comes to XML-syntax in matlab. That’s why I need a bit more help than others.
I have the following XML-file which is located in the folder c:\Data\Testfile.xml
<?xml version='1.0' encoding='UTF-8'?>
<tns:testBenchConfiguration>
<tns:instrumentList/>
<tns:VariableList>
<tns:Variable>
<tns:value>1</tns:value>
<tns:format>double</tns:format>
<tns:description/>
<tns:tag/>
<tns:path>Model Root/general/Value</tns:path>
<tns:guiName>approval</tns:guiName>
</tns:Variable>
</tns:VariableList>
</tns:testBenchConfiguration>
Now I want to open this XML file with matlab, change the value from "1" to "2" and save the change afterwards.
I use matlab 2015, if this is important
Robert Ungi
Robert Ungi on 3 Jan 2022
@Heinke W this might help:
% <?xml version="1.0" encoding="utf-8"?>
% <xml>
% <busStop endPos="30" id="BusStop0" lane="1to2_0" startPos="20"/>
% <busStop endPos="80" id="BusStop1" lane="1to2_0" startPos="70"/>
% <chargingStation chrgPower="220" endPos="30" id="ChrgStn1" lane="1to2_0" startPos="45"/>
% </xml>
import javax.xml.xpath.*
factory = XPathFactory.newInstance;
import javax.script.ScriptContext;
xpath = factory.newXPath;
fXML=xmlread('SampleXML.xml');
expression = xpath.compile('xml/chargingStation[@id="ChrgStn1"]');
chargingStation = expression.evaluate(fXML, XPathConstants.NODESET);
for i=0:chargingStation.getLength-1
chargingStation.item(i).setAttribute('startPos', "45")
end
xmlwrite('SampleXMLOut.xml', fXML);
Adopted from The Wizzart.

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