@Override
    public void setDocumentLocator(final Locator locator) {
        // Just remember the locator in case we start to output a document.
        this.locator = locator;
        super.setDocumentLocator(locator);
    }
This filter is used to buffer SAX events in memory if required. Having
buffered SAX events this filter can then fire them at a content handler.
stroom-pipeline/src/main/java/stroom/pipeline/record/XMLRecordEmitter.java