XML shredding via XSLT in Java

Question

I need to transform large XML files that have a nested (hierarchical) structure of the form

   Flat XML
   Hierarchical XML (multiple blocks, so         


        

Answer 1

Here is a generic solution as requested:

<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="pLeafNodes" select="//Level-4"/>

 <xsl:template match="/">
  <t>
    <xsl:call-template name="StructRepro"/>
  </t>
 </xsl:template>

 <xsl:template name="StructRepro">
   <xsl:param name="pLeaves" select="$pLeafNodes"/>

   <xsl:for-each select="$pLeaves">
     <xsl:apply-templates mode="build" select="/*">
      <xsl:with-param name="pChild" select="."/>
      <xsl:with-param name="pLeaves" select="$pLeaves"/>
     </xsl:apply-templates>
   </xsl:for-each>
 </xsl:template>

  <xsl:template mode="build" match="node()|@*">
      <xsl:param name="pChild"/>
      <xsl:param name="pLeaves"/>

     <xsl:copy>
       <xsl:apply-templates mode="build" select="@*"/>

       <xsl:variable name="vLeafChild" select=
         "*[count(.|$pChild) = count($pChild)]"/>

       <xsl:choose>
        <xsl:when test="$vLeafChild">
         <xsl:apply-templates mode="build"
             select="$vLeafChild
                    |
                      node()[not(count(.|$pLeaves) = count($pLeaves))]">
             <xsl:with-param name="pChild" select="$pChild"/>
             <xsl:with-param name="pLeaves" select="$pLeaves"/>
         </xsl:apply-templates>
        </xsl:when>
        <xsl:otherwise>
         <xsl:apply-templates mode="build" select=
         "node()[not(.//*[count(.|$pLeaves) = count($pLeaves)])
                or
                 .//*[count(.|$pChild) = count($pChild)]
                ]
         ">

             <xsl:with-param name="pChild" select="$pChild"/>
             <xsl:with-param name="pLeaves" select="$pLeaves"/>
         </xsl:apply-templates>
        </xsl:otherwise>
       </xsl:choose>
     </xsl:copy>
 </xsl:template>
 <xsl:template match="text()"/>
</xsl:stylesheet>

When applied on the provided simplified (and generic) XML document:

<Level-1>
   ...
   <Level-2>
      ...
      <Level-3>
        ...
        <Level-4>A</Level-4>
        <Level-4>B</Level-4>
        ...
      </Level-3>
      ...
   </Level-2>
   ...
</Level-1>

the wanted, correct result is produced:

<Level-1>
   ...
   <Level-2>
      ...
      <Level-3>
         <Level-4>A</Level-4>
      </Level-3>
      ...
   </Level-2>
   ...
</Level-1>
<Level-1>
   ...
   <Level-2>
      ...
      <Level-3>
         <Level-4>B</Level-4>
      </Level-3>
      ...
   </Level-2>
   ...
</Level-1>

Now, if we change the line:

 <xsl:param name="pLeafNodes" select="//Level-4"/>

to:

 <xsl:param name="pLeafNodes" select="//Job"/>

and apply the transformation to the Employee XML document:

<Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
        <Employment country="US">
            <Comment>List of previous jobs in the US</Comment>
            <Jobs>3</Jobs>
            <JobDetails>
                <Job title = "Senior Developer">
                    <StartDate>01/10/2001</StartDate>
                    <Months>38</Months>
                </Job>
                <Job title = "Senior Developer">
                    <StartDate>01/12/2004</StartDate>
                    <Months>6</Months>
                </Job>
                <Job title = "Senior Developer">
                    <StartDate>01/06/2005</StartDate>
                    <Months>10</Months>
                </Job>
            </JobDetails>
        </Employment>
    </EmploymentHistory>
    <EmploymentHistory>
        <Employment country="UK">
            <Comment>List of previous jobs in the UK</Comment>
            <Jobs>2</Jobs>
            <JobDetails>
                <Job title = "Junior Developer">
                    <StartDate>01/05/1999</StartDate>
                    <Months>25</Months>
                </Job>
                <Job title = "Junior Developer">
                    <StartDate>01/07/2001</StartDate>
                    <Months>3</Months>
                </Job>
            </JobDetails>
        </Employment>
    </EmploymentHistory>
    <Available>true</Available>
    <Experience unit="years">6</Experience>
</Employee>

we again get the wanted, correct result:

<t>
   <Employee name="A Name">
      <Address>123 A Street</Address>
      <Age>28</Age>
      <EmploymentHistory>
         <Employment country="US">
            <Comment>List of previous jobs in the US</Comment>
            <Jobs>3</Jobs>
            <JobDetails>
               <Job title="Senior Developer">
                  <StartDate>01/10/2001</StartDate>
                  <Months>38</Months>
               </Job>
            </JobDetails>
         </Employment>
      </EmploymentHistory>
      <Available>true</Available>
      <Experience unit="years">6</Experience>
   </Employee>
   <Employee name="A Name">
      <Address>123 A Street</Address>
      <Age>28</Age>
      <EmploymentHistory>
         <Employment country="US">
            <Comment>List of previous jobs in the US</Comment>
            <Jobs>3</Jobs>
            <JobDetails>
               <Job title="Senior Developer">
                  <StartDate>01/12/2004</StartDate>
                  <Months>6</Months>
               </Job>
            </JobDetails>
         </Employment>
      </EmploymentHistory>
      <Available>true</Available>
      <Experience unit="years">6</Experience>
   </Employee>
   <Employee name="A Name">
      <Address>123 A Street</Address>
      <Age>28</Age>
      <EmploymentHistory>
         <Employment country="US">
            <Comment>List of previous jobs in the US</Comment>
            <Jobs>3</Jobs>
            <JobDetails>
               <Job title="Senior Developer">
                  <StartDate>01/06/2005</StartDate>
                  <Months>10</Months>
               </Job>
            </JobDetails>
         </Employment>
      </EmploymentHistory>
      <Available>true</Available>
      <Experience unit="years">6</Experience>
   </Employee>
   <Employee name="A Name">
      <Address>123 A Street</Address>
      <Age>28</Age>
      <EmploymentHistory>
         <Employment country="UK">
            <Comment>List of previous jobs in the UK</Comment>
            <Jobs>2</Jobs>
            <JobDetails>
               <Job title="Junior Developer">
                  <StartDate>01/05/1999</StartDate>
                  <Months>25</Months>
               </Job>
            </JobDetails>
         </Employment>
      </EmploymentHistory>
      <Available>true</Available>
      <Experience unit="years">6</Experience>
   </Employee>
   <Employee name="A Name">
      <Address>123 A Street</Address>
      <Age>28</Age>
      <EmploymentHistory>
         <Employment country="UK">
            <Comment>List of previous jobs in the UK</Comment>
            <Jobs>2</Jobs>
            <JobDetails>
               <Job title="Junior Developer">
                  <StartDate>01/07/2001</StartDate>
                  <Months>3</Months>
               </Job>
            </JobDetails>
         </Employment>
      </EmploymentHistory>
      <Available>true</Available>
      <Experience unit="years">6</Experience>
   </Employee>
</t>

Explanation: The processing is done in a named template (StructRepro) and controlled by a single external parameter named pLeafNodes, that must contain a nodeset of all nodes whose "upward structure" is to be reproduced in the result.

Answer 2

Given the following XML:

<?xml version="1.0" encoding="utf-8" ?>
<Employee name="A Name">
  <Address>123 A Street</Address>
  <Age>28</Age>
  <EmploymentHistory>
    <Employment country="US">
      <Comment>List of previous jobs in the US</Comment>
      <Jobs>3</Jobs>
      <JobDetails>
        <Job title = "Developer">
          <StartDate>01/10/2001</StartDate>
          <Months>38</Months>
        </Job>
        <Job title = "Developer">
          <StartDate>01/12/2004</StartDate>
          <Months>6</Months>
        </Job>
        <Job title = "Developer">
          <StartDate>01/06/2005</StartDate>
          <Months>10</Months>
        </Job>
      </JobDetails>
      </Employment>
      <Employment country="UK">
        <Comment>List of previous jobs in the UK</Comment>
        <Jobs>2</Jobs>
        <JobDetails>
          <Job title = "Developer">
            <StartDate>01/05/1999</StartDate>
            <Months>25</Months>
          </Job>
          <Job title = "Developer">
            <StartDate>01/07/2001</StartDate>
            <Months>3</Months>
          </Job>
        </JobDetails>
        </Employment>
  </EmploymentHistory>
  <Available>true</Available>
  <Experience unit="years">6</Experience>
</Employee>

The following XSLT:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl">

    <xsl:output method="xml" indent="yes"/>

    <xsl:template match="/">
      <Output>
        <xsl:apply-templates select="//Employee/EmploymentHistory/Employment/JobDetails/Job" />
      </Output>
    </xsl:template>

  <xsl:template match="//Employee/EmploymentHistory/Employment/JobDetails/Job">
    <Employee>
      <xsl:attribute name="name">
        <xsl:value-of select="ancestor::Employee/@name"/>
      </xsl:attribute>
      <Address>
        <xsl:value-of select="ancestor::Employee/Address"/>
      </Address>
      <Age>
        <xsl:value-of select="ancestor::Employee/Age"/>
      </Age>
      <EmploymentHistory>
        <Employment>
          <xsl:attribute name="country">
            <xsl:value-of select="ancestor::Employment/@country"/>
          </xsl:attribute>
          <Comment>
            <xsl:value-of select="ancestor::Employment/Comment"/>
          </Comment>
          <Jobs>
            <xsl:value-of select="ancestor::Employment/Jobs"/>
          </Jobs>
          <JobDetails>
            <xsl:copy-of select="."/>
          </JobDetails>
          <Available>
            <xsl:value-of select="ancestor::Employee/Available"/>
          </Available>
          <Experience>
            <xsl:attribute name="unit">
              <xsl:value-of select="ancestor::Employee/Experience/@unit"/>
            </xsl:attribute>
            <xsl:value-of select="ancestor::Employee/Experience"/>
          </Experience>
        </Employment>
      </EmploymentHistory>
    </Employee>

  </xsl:template>


</xsl:stylesheet>

Gives the following output:

<?xml version="1.0" encoding="utf-8"?>
<Output>
  <Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
      <Employment country="US">
        <Comment>List of previous jobs in the US</Comment>
        <Jobs>3</Jobs>
        <JobDetails>
          <Job title="Developer">
          <StartDate>01/10/2001</StartDate>
          <Months>38</Months>
        </Job>
        </JobDetails>
        <Available>true</Available>
        <Experience unit="years">6</Experience>
      </Employment>
    </EmploymentHistory>
  </Employee>
  <Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
      <Employment country="US">
        <Comment>List of previous jobs in the US</Comment>
        <Jobs>3</Jobs>
        <JobDetails>
          <Job title="Developer">
          <StartDate>01/12/2004</StartDate>
          <Months>6</Months>
        </Job>
        </JobDetails>
        <Available>true</Available>
        <Experience unit="years">6</Experience>
      </Employment>
    </EmploymentHistory>
  </Employee>
  <Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
      <Employment country="US">
        <Comment>List of previous jobs in the US</Comment>
        <Jobs>3</Jobs>
        <JobDetails>
          <Job title="Developer">
          <StartDate>01/06/2005</StartDate>
          <Months>10</Months>
        </Job>
        </JobDetails>
        <Available>true</Available>
        <Experience unit="years">6</Experience>
      </Employment>
    </EmploymentHistory>
  </Employee>
  <Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
      <Employment country="UK">
        <Comment>List of previous jobs in the UK</Comment>
        <Jobs>2</Jobs>
        <JobDetails>
          <Job title="Developer">
            <StartDate>01/05/1999</StartDate>
            <Months>25</Months>
          </Job>
        </JobDetails>
        <Available>true</Available>
        <Experience unit="years">6</Experience>
      </Employment>
    </EmploymentHistory>
  </Employee>
  <Employee name="A Name">
    <Address>123 A Street</Address>
    <Age>28</Age>
    <EmploymentHistory>
      <Employment country="UK">
        <Comment>List of previous jobs in the UK</Comment>
        <Jobs>2</Jobs>
        <JobDetails>
          <Job title="Developer">
            <StartDate>01/07/2001</StartDate>
            <Months>3</Months>
          </Job>
        </JobDetails>
        <Available>true</Available>
        <Experience unit="years">6</Experience>
      </Employment>
    </EmploymentHistory>
  </Employee>
</Output>

Note that I've added an Output root element to ensure the document is well formed.

Is this what you wanted?

You might also be able to use xsl:copy to copy the higher level elements, but I need to think about this one a bit more. With the above xslt, you have more control, but also you have to redefine your elements...