How to change a value in a XML-File?

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!!!

Answer 1

[Alessandro]

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

[Moritz]

Can it be easier?

The XML does already exist! I just want to change the value!?

Can i do it with xmlread or xmlwrite?

Thanks!!

[Alessandro]

Ok sorry I thought you wannt to change the node. That it is much more simplier:

Doc.getElementsByTagName('chargingStation').item(0).setAttribute('startPos','55') Doc.getElementsByTagName('chargingStation').item(0).setAttribute('endPos','75')

[Heinke W]

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]

@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.