Replace an attribute in xml with xpath

Question

I want to take an attribute found thru xpath and replace it in the Document.

This is the xml:

<MineX STATE="add">
  <Desc F_CREATOR="admin" F_ENTRYDATE="2010-12-24" F_HEIGHT="0.875" F_ID="1" F_LEFT="1.15625" F_LINE_COLOR="255" F_FORECOLOR="0">
    <F_CUSTOM_BYTES></F_CUSTOM_BYTES>
  </Desc>
</MineX>

With Java, I can retrieve the value like this:

org.w3c.dom.Document xmlDoc = getDoc(path);
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();

XPathExpression myExp = xpath.compile("//MineX/Desc/@F_LINE_COLOR");
System.out.println("Line color:" + (String)myExp.evaluate(xmlDoc, XPathConstants.STRING) + "\n");

This prints out: 255

So, what XPath function will allow me to replace the 255, for another string? Or do I need something other than XPath for this?

Answer 1

So, what XPath function will allow me to replace the 255, for another string? Or do I need something other than XPath for this?

XPath is the query language for XML and as such cannot modify an XML document .

In order to modify an XML document one needs to use the programming language (such as XSLT, C#, JS, PHP, ..., etc) that is hosting XPath.

Here is a solution, where the hosting language is XSLT :

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:param name="pNewLineColor" select="123"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="@F_LINE_COLOR">
  <xsl:attribute name="{name()}">
    <xsl:value-of select="$pNewLineColor"/>
  </xsl:attribute>
 </xsl:template>
</xsl:stylesheet>

when this transformation is applied on the provided XML document :

<MineX STATE="add">
    <Desc F_CREATOR="admin"
          F_ENTRYDATE="2010-12-24"
          F_HEIGHT="0.875"
          F_ID="1"
          F_LEFT="1.15625"
          F_LINE_COLOR="255"
          F_FORECOLOR="0">
        <F_CUSTOM_BYTES></F_CUSTOM_BYTES>
    </Desc>
</MineX>

the wanted, correct result is produced :

<MineX STATE="add">
    <Desc F_CREATOR="admin"
          F_ENTRYDATE="2010-12-24"
          F_HEIGHT="0.875"
          F_ID="1"
          F_LEFT="1.15625"
          F_LINE_COLOR="123"
          F_FORECOLOR="0">
        <F_CUSTOM_BYTES></F_CUSTOM_BYTES>
    </Desc>
</MineX>

Answer 2

XPath is a query language for extracting information out of an XML file. As far as I know it is not suited for replacing or editing data in an XML. One way to transform an XML is via XSLT.