Question

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

<Root>
   Flat XML
   Hierarchical XML (multiple blocks, some repetitive)
   Flat XML
</Root>

into a flatter (“shredded”) form, with 1 block for each repetitive nested block.

The data has numerous different tags and hierarchy variations (especially in the number of tags of the shredded XML before and after the hierarchical XML), so ideally no assumption should be made about tag and attribute names, or the hierarchical level.

A top-level view of the hierarchy for just 4 levels would look something like

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

and the desired output would then be

<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>

That is, if at each level i there are Li different components, a total of Product(Li) different components will be produced (just 2 above, since the only differentiating factor is Level 4, so L1*L2*L3*L4 = 2).

From what I have seen around, XSLT may be the way to go, but any other solution (e.g., StAX or even JDOM) would do.

A more detailed example, using fictitious information, would be

<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>

The above data should be shredded into 5 blocks (i.e., one for each different <Job> block), each of which will leave all other tags identical and just have a single <Job> element. So, given the 5 different <Job> blocks in the above example, the transformed (“shredded”) XML would be

<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>
      <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 = "Senior 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 = "Senior 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>3</Jobs>
      <JobDetails>
        <Job title = "Junior 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>3</Jobs>
      <JobDetails>
        <Job title = "Junior Developer">
          <StartDate>01/07/2001</StartDate>
          <Months>3</Months>
        </Job>
      </JobDetails>
      <Available>true</Available>
     <Experience unit="years">6</Experience>
    </Employment>
  </EmploymentHistory>
</Employee>

Answer 1

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…