Sax Dom Tutorial

Roadmap ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What are XML APIs for? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Overview of JAXP ,[object Object],[object Object],[object Object],Defines the XSLT APIs that let you transform XML into other forms. (Not covered today.) javax.xml.transform Defines the basic SAX APIs. org.xml.sax Defines the Document class (a DOM), as well as classes for all of the components of a DOM. org.w3c.dom The main JAXP APIs, which provide a common interface for various SAX and DOM parsers. javax.xml.parsers

JAXP XML Parsers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

SAX vs. DOM ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],SAX = Simple API for XML DOM = Document Object Model There is also JDOM … more later

Using SAX ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],(This reflects SAX 1, which you can still use, but SAX 2 prefers a new incantation…) Here’s the standard recipe for starting with SAX:

Using SAX 2 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],But where does myContentHandler come from? In SAX 2, the following usage is preferred:

Defining a ContentHandler ,[object Object],[object Object],[object Object],startDocument () // receive notice of start of document endDocument () // receive notice of end of document startElement () // receive notice of start of each element endElement () // receive notice of end of each element characters () // receive a chunk of character data error () // receive notice of recoverable parser error // ...plus more...

startElement() and endElement() ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],startElement ( String namespaceURI, // for use w/ namespaces String localName, // for use w/ namespaces String qName, // "qualified" name -- use this one! Attributes atts) endElement ( String namespaceURI, String localName, String qName) The SAXParser invokes your callbacks to notify you of events:

SAX Attributes ,[object Object],[object Object],getLength () // return number of attributes getIndex ( String qName ) // look up attribute's index by qName getValue ( String qName ) // look up attribute's value by qName getValue ( int index ) // look up attribute's value by index // ... and others ...

SAX characters() ,[object Object],[object Object],public void characters ( char [] ch , // buffer containing chars int start , // start position in buffer int length ) // num of chars to read The characters () event handler receives notification of character data (i.e. content that is not part of an XML element):

SAXExample : Input XML <?xml version="1.0" encoding="UTF-8"?> <dots> this is before the first dot and it continues on multiple lines <dot x="9" y="81" /> <dot x="11" y="121" /> <flip> flip is on <dot x="196" y="14" /> <dot x="169" y="13" /> </flip> flip is off <dot x="12" y="144" /> <extra> stuff </extra>  </dots>

SAXExample : Code Please see SAXExample.java

SAXExample : Input  Output startDocument startElement: dots (0 attributes) characters: this is before the first dot and it continues on multiple lines startElement: dot (2 attributes) endElement: dot startElement: dot (2 attributes) endElement: dot startElement: flip (0 attributes) characters: flip is on startElement: dot (2 attributes) endElement: dot startElement: dot (2 attributes) endElement: dot endElement: flip characters: flip is off startElement: dot (2 attributes) endElement: dot startElement: extra (0 attributes) characters: stuff endElement: extra endElement: dots endDocument Finished parsing input. Got the following dots: [(9, 81), (11, 121), (14, 196), (13, 169), (12, 144)] <?xml version="1.0" encoding="UTF-8"?> <dots> this is before the first dot and it continues on multiple lines <dot x="9" y="81" /> <dot x="11" y="121" /> <flip> flip is on <dot x="196" y="14" /> <dot x="169" y="13" /> </flip> flip is off <dot x="12" y="144" /> <extra> stuff </extra>  </dots>

DOM Document Structure Document +--- Element <dots> +--- Text "this is before the first dot | and it continues on multiple lines" +--- Element <dot> +--- Text "" +--- Element <dot> +--- Text "" +--- Element <flip> | +--- Text "flip is on" | +--- Element <dot> | +--- Text "" | +--- Element <dot> | +--- Text "" +--- Text "flip is off" +--- Element <dot> +--- Text "" +--- Element <extra> | +--- Text "stuff" +--- Text "" +--- Comment "a final comment" +--- Text "" XML Input: Document structure: ,[object Object],[object Object],[object Object],<?xml version="1.0" encoding="UTF-8"?> <dots> this is before the first dot and it continues on multiple lines <dot x="9" y="81" /> <dot x="11" y="121" /> <flip> flip is on <dot x="196" y="14" /> <dot x="169" y="13" /> </flip> flip is off <dot x="12" y="144" /> <extra> stuff </extra>  </dots>

Using DOM import javax.xml.parsers.* ; import org.w3c.dom.* ; // get a DocumentBuilder object DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = null; try { db = dbf.newDocumentBuilder(); } catch ( ParserConfigurationException e ) { e.printStackTrace(); } // invoke parser to get a Document Document doc = db.parse(inputStream); Document doc = db.parse(file); Document doc = db.parse(url); Here’s the basic recipe for getting started with DOM:

DOM Document access idioms // get the root of the Document tree Element root = doc.getDocumentElement(); // get nodes in subtree by tag name NodeList dots = root.getElementsByTagName( "dot" ); // get first dot element Element firstDot = ( Element ) dots.item(0); // get x attribute of first dot String x = firstDot.getAttribute( "x" ); OK, say we have a Document . How do we get at the pieces of it? Here are some common idioms:

More Document accessors Node access methods: String getNodeName () short getNodeType () Document getOwnerDocument () boolean hasChildNodes () NodeList getChildNodes () Node getFirstChild () Node getLastChild () Node getParentNode () Node getNextSibling () Node getPreviousSibling () boolean hasAttributes () ... and more ... Element extends Node and adds these access methods: String getTagName () boolean hasAttribute ( String name ) String getAttribute ( String name ) NodeList getElementsByTagName ( String name ) … and more … Document extends Node and adds these access methods: Element getDocumentElement () DocumentType getDoctype () ... plus the Element methods just mentioned ... ... and more ... e.g. DOCUMENT_NODE , ELEMENT_NODE , TEXT_NODE , COMMENT_NODE , etc.

Creating & manipulating Document s // get new empty Document from DocumentBuilder Document doc = db.newDocument(); // create a new <dots> Element and add to Document as root Element root = doc.createElement( "dots" ); doc.appendChild(root); // create a new <dot> Element and add as child of root Element dot = doc.createElement( "dot" ); dot.setAttribute( "x" , "9" ); dot.setAttribute( "y" , "81" ); root.appendChild(dot); The DOM API also includes lots of methods for creating and manipulating Document objects:

More Document manipulators Node manipulation methods: void setNodeValue ( String nodeValue ) Node appendChild ( Node newChild ) Node insertBefore ( Node newChild , Node refChild ) Node removeChild ( Node oldChild ) ... and more ... Element manipulation methods: void setAttribute ( String name , String value ) void removeAttribute ( String name ) … and more … Document manipulation methods: Text createTextNode ( String data ) Comment createCommentNode ( String data ) ... and more ...

Writing a Document as XML ,[object Object],[object Object],[object Object],[object Object],[object Object],import org.apache.crimson.tree.XmlDocument ; XmlDocument x = ( XmlDocument ) doc; x.write(out, "UTF-8" );

Sax Dom Tutorial

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