@Override
    public void setDocumentLocator(final Locator locator) {
        contentHandler.setDocumentLocator(locator);
    }
Receive an object for locating the origin of SAX document events.
<p>
<p>
SAX parsers are strongly encouraged (though not absolutely required) to
supply a locator: if it does so, it must supply the locator to the
application by invoking this method before invoking any of the other
methods in the ContentHandler interface.
</p>
<p>
<p>
The locator allows the application to determine the end position of any
document-related event, even if the parser is not reporting an error.
Typically, the application will use this information for reporting its
own errors (such as character content that does not match an
application's business rules). The information returned by the locator is
probably not sufficient for use with a search engine.
</p>
<p>
<p>
Note that the locator will return correct information only during the
invocation SAX event callbacks after {@link #startDocument startDocument}
returns and before {@link #endDocument endDocument} is called. The
application should not attempt to use it at any other time.
</p>

@param locator an object that can return the location of any SAX document
               event
@see org.xml.sax.Locator
stroom-pipeline/src/main/java/stroom/pipeline/filter/AbstractXMLFilter.java