XML Tools

1. XML Tools

2. DOM The Document Object Model (DOM) is a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content and structure of XML documents. The following is part of the DOM interface: public interface Node { public String getNodeName (); public String getNodeValue (); public NodeList getChildNodes (); public NamedNodeMap getAttributes (); ... } public interface Element extends Node { public Node getElementsByTagName ( String name ); ... } public interface Document extends Node { public Element getDocumentElement (); ... } public interface NodeList { public Node item ( int index ); public int getLength (); public Node item ( int index ); }

3. DOM Example import java.io.File; import javax.xml.parsers.*; import org.w3c.dom.*; class Test { public static void main ( String args[] ) throws Exception { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document doc = db.parse(new File("depts.xml")); NodeList nodes = doc.getDocumentElement().getChildNodes(); for (int i=0; i<nodes.getLength(); i++) { Node n = nodes.item(i); NodeList ndl = n.getChildNodes(); for (int k=0; k<ndl.getLength(); k++) { Node m = ndl.item(k); if ( (m.getNodeName() == "dept") && (m.getFirstChild().getNodeValue() == "cse") ) { NodeList ncl = ((Element) m).getElementsByTagName("tel"); for (int j=0; j<ncl.getLength(); j++) { Node nc = ncl.item(j); System.out.print(nc.getFirstChild().getNodeValue()); } } } } } }

4. SAX SAX is the Simple API for XML that allows you to process a document as it's being read (in contrast to DOM, which requires the entire document to be read before it takes any action). The SAX API is event based. The XML parser sends events, such as the start or the end of an element, to an event handler, which processes the information. Parser events: void startDocument () Receive notification of the beginning of a document. void endDocument () Receive notification of the end of a document. void startElement ( String namespace, String localName, String qName, Attributes atts ) Receive notification of the beginning of an element. void endElement ( String namespace, String localName, String qName ) Receive notification of the end of an element. void characters ( char[] ch, int start, int length ) Receive notification of character data.

5. SAX Example import java.io.FileReader; import javax.xml.parsers.*; import org.xml.sax.*; import org.xml.sax.helpers.*; class SimpleHandler extends DefaultHandler { public static void main ( String args[] ) throws Exception { SAXParserFactory pf = SAXParserFactory.newInstance(); SAXParser parser = pf.newSAXParser(); XMLReader reader = parser.getXMLReader(); SimpleHandler handler = new SimpleHandler(); parser.parse(new InputSource(new FileReader("a.xml")), handler); } public SimpleHandler () { super(); }

6. SAX Example (cont.) public void startDocument () { System.out.println("Start document"); } public void endDocument () { System.out.println("End document"); } public void startElement ( String uri, String name, String tag, Attributes atts ) { System.out.println("Start element: " + tag); } public void endElement ( String uri, String name, String tag ) { System.out.println("End element: " + tag); } public void characters ( char text[], int start, int length ) { System.out.print("Characters: \""); for (int i = start; i < start + length; i++) System.out.print(text[i]); System.out.print("\"\n"); } }

7. XSL Transformation A stylesheet specification language for converting XML documents into various forms (XML, HTML, plain text, etc). • Can transform each XML element into another element, add new elements into the output file, or remove elements. • Can rearrange and sort elements, test and make decisions about which elements to display, and much more. • Based on Xpath: <xsl:stylesheet version=’1.0’ xmlns:xsl=’http//www.w3.org/1999/XSL/Transform’> <students> <xsl:copy-of select=”//student/name”/> </students> </xsl:stylesheet>

8. XSLT Templates • XSL uses XPath to define parts of the source document that match one or more predefined templates. • When a match is found, XSLT will transform the matching part of the source document into the result document. • The parts of the source document that do not match a template will end up unmodified in the result document. Form: <xsl:template match=”XPath expression”> … </xsl:template> The default (implicit) templates visit all nodes and strip out all tags: <xsl:template match=”*|/”> <xsl:apply-templates/> </xsl:template> <xsl:template match=“text()|@*"> <xsl:value-of select=“.”/> </xsl:template>

9. Other XSLT Elements <xsl:value-of select=“XPath expression“/> select the value of an XML element and add it to the output stream of the transformation, e.g. <xsl:value-of select="//books/book/author"/>. <xsl:copy-of select=“XPath expression“/> copy the entire XML element to the output stream of the transformation. <xsl:apply-templates match=“XPath expression“/> apply the template rules to the elements that match the XPath expression. <xsl:element name=“XPath expression“> … </xsl:element> add an element to the output with a tag-name derived from the XPath. Example: <xsl:stylesheet version = ’1.0’ xmlns:xsl=’http://www.w3.org/1999/XSL/Transform’> <xsl:template match="employee"> <b> <xsl:apply-templates select="."/> </b> </xsl:template> <xsl:template match="surname"> <i> <xsl:value-of select="."/> </i> </xsl:template> </xsl:stylesheet>

10. Copy the Entire Document <xsl:stylesheet version = ’1.0’ xmlns:xsl=’http://www.w3.org/1999/XSL/Transform’> <xsl:template match=“/"> <xsl:apply-templates/> </xsl:template> <xsl:template match=“text()"> <xsl:value-of select=“.”/> </xsl:template> <xsl:template match=“*"> <xsl:element name=“name(.)”> <xsl:apply-templates/> </xsl:element> </xsl:template> </xsl:stylesheet>

11. More on XSLT • Conflict resolution: more specific templates overwrite more general templates. Templates are assigned default priorities, but they can be overwritten using priority=“n” in a template. • Modes can be used to group together templates. No mode is an empty mode. <xsl:template match=“…” mode=“A”> <xsl:apply-templates mode=“B”/> </xsl:template> • Conditional and loop statements: <xsl:if test=“XPath predicate”> body </xsl:if> <xsl:for-each select=“XPath”> body </xsl:for-each> • Variables can be used to name data: <xsl:variable name=“x”> value </xsl:variable> Variables are used as {$x} in XPaths.

12. Using XSLT import java.io.FileReader; import javax.xml.parsers.*; import org.xml.sax.*; import org.xml.sax.helpers.*; import javax.xml.transform.*; import javax.xml.transform.sax.*; import javax.xml.transform.stream.*; class Test { public static void main ( String args[] ) throws Exception { TransformerFactory tfactory = TransformerFactory.newInstance(); SAXParserFactory pfactory = SAXParserFactory.newInstance(); SAXParser parser = pfactory.newSAXParser(); XMLReader reader = parser.getXMLReader(); SimpleHandler handler = new SimpleHandler(); Transformer t = tfactory.newTransformer(new StreamSource("x.xsl")); SAXSource source = new SAXSource(reader,new InputSource("a.xml")); t.transform(source,new StreamResult("a.html")); } }