@PipelineProperty(
            description = "Header text that can be added to the output at the start.",
            displayPriority = 1)
    public void setHeader(final String header) {
        try {
            if (header == null) {
                this.header = null;
            } else {
                this.header = StringEscapeUtils.unescapeJava(header).getBytes();
            }
        } catch (final RuntimeException e) {
            throw ProcessException.wrap(e);
        }
    }
Writes characters.

@param ch     An array of characters.
@param start  The starting position in the array.
@param length The number of characters to use from the array.
@throws org.xml.sax.SAXException The client may throw an exception during processing.
@see stroom.pipeline.filter.AbstractXMLFilter#characters(char[],
int, int)
stroom-pipeline/src/main/java/stroom/pipeline/writer/TextWriter.java