code: protected void addSingleUpsertToSqlMap(Document document, IntrospectedTable introspectedTable) {
      XmlElement update = new XmlElement("update");
      update.addAttribute(new Attribute("id", UPSERT));
      update.addAttribute(new Attribute("parameterType", "map"));
  
      generateSqlMapContent(introspectedTable, update);
  
      document.getRootElement().addElement(update);
    }
docs: add update xml element to mapper.xml for upsert
  
  @param document          The generated xml mapper dom
  @param introspectedTable The metadata for database table