XML generation using SAXTransformer in Java JDK

XML generation is a common found requirement in applications. Typical way to address it in java is to manually append the XML string in a StringBuffer. Firstly this can be quite tedious. Secondly it is susceptible to manual errors while writing the XML. Also, the developer needs to take care of the escape characters etc. Clearly this is not the best way of XML generation in Java.
A better way of achieving this is to use the classes in javax.xml.transform package of JDK. These are traditionally used for XML parsing and transformations. Their use of XML generation is uncommon and unobvious. here's a code snippet that shows how these classes can be used for XML generation:

SAXTransformerFactory saxFactory = (SAXTransformerFactory) TransformerFactory.newInstance();
StringWriter writer = new StringWriter();
try {
TransformerHandler handler = saxFactory.newTransformerHandler();
Result result = new StreamResult(writer);
handler.setResult(result);
handler.startDocument();
AttributesImpl atts = new AttributesImpl();
atts.addAttribute("", "", "name", "CDATA", "");
atts.addAttribute("", "", "version", "CDATA", "6.2");
handler.startElement("http://wbe.ibm.com/6.2/Event/connect", "","connector", atts);
atts.clear();
atts.addAttribute("", "", "name", "CDATA", "connect");
atts.addAttribute("", "", "type", "CDATA", "Event");
handler.startElement("", "", "connector-bundle", atts);
atts.clear();
handler.startElement("", "", "connect", atts);
String paramValue = null;
for (ScenarioParameter param : scenarioParams) {
atts.clear();
atts.addAttribute("", "", "type", "CDATA", param.getType());
handler.startElement("", "", param.getName(), atts);
paramValue = getParamValue(param.getParamId(), params);
handler.characters(paramValue.toCharArray(), 0, paramValue.length());
handler.endElement("", "", param.getName());
}
handler.endElement("", "", "connect");
handler.endElement("", "", "connector-bundle");
atts.clear();
handler.startElement("", "", "system", atts);
String systemName = InetAddress.getLocalHost().getHostName();
handler.characters(systemName.toCharArray(), 0, systemName.length());
handler.endElement("", "", "system");
handler.startElement("", "", "timestamp", atts);
String timestamp = new Date().toString();
handler.characters(timestamp.toCharArray(), 0, timestamp.length());
handler.endElement("", "", "timestamp");
handler.startElement("", "", "loginfo", atts);
String logMsg = "Sending values at runtime";
handler.characters(logMsg.toCharArray(), 0, logMsg.length());
handler.endElement("", "", "loginfo");
handler.endElement("", "", "connector");
handler.endDocument();

System.out.println(writer.toString());

TransformerHandler listens for XML parse events and transforms them to Result. Since we are not using it for parsing, here the handler generates those events like startDocument, startElement and transforms them into Result. The Result thus contains the XML that we wanted to generate. Note that it is the developer's responsibility to take care of the well formedness of the XML. A startElement has to have a matching endElement and a startDocument has to have a matching endDocument.

~Ashish.