xslt - How to merge two XML files

Question

I have two xml files, which need to be merged into one xml. Here is the example:

orginal.xml file ：

<employees>
  <employee id="1">
    <name> Name1 </name>
    <email> email1 <email>
  </employee>
  <employee id="2">
    <name> Name2 </name>
    <email> email2 <email>
  </employee>
</employees>

update.xml file:

<employees>
        <employee id="2">
            <name> Name2 </name>
            <email> email_New <email>
        </employee>
        <employee id="3">
            <name> Name3 </name>
            <email> email3 <email>
        </employee>
</employees>

they should be merged to a xml file like this:

<employees>
  <employee id="1">
    <name> Name1 </name>
    <email> email1 <email>
  </employee>  
  <employee id="2">
    <name> Name2 </name>
    <email> email_New <email>
  </employee>
  <employee id="3">
    <name> Name3 </name>
    <email> email3 <email>
  </employee>
</employees>

Actually, I'd like to use the update.xml to update the orginal.xml :

1. new employee in update.xml should be added to original.xml

2. modified employee information in update.xml should overwrite the corresponding employee node.

I know a little of XSLT, but my knowledge is not enough to figure out the right XSLT for the merge.

Answer 1

Please give this a try:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>
  <xsl:param name="fileName" select="'update.xml'" />
  <xsl:param name="updates" select="document($fileName)" />

  <xsl:variable name="updateEmployees" select="$updates/employees/employee" />

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

  <xsl:template match="employees">
    <xsl:copy>
      <xsl:apply-templates select="employee[not(@id = $updateEmployees/@id)]" />
      <xsl:apply-templates select="$updateEmployees" />
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>

When run with your first XML as the input and with the update.xml present in the same folder, this produces:

<employees>
  <employee id="1">
    <name> Name1 </name>
    <email>
      email1 </email>
  </employee>
  <employee id="2">
    <name> Name2 </name>
    <email>
      email_New
    </email>
  </employee>
  <employee id="3">
    <name> Name3 </name>
    <email>
      email3
    </email>
  </employee>
</employees>

fileName and updates are declared as parameters, so if the updates are in a file named something other than "update.xml" or you want to pass the update XML in directly, you can do that without making any modifications to the XSLT.