Apache DOM Parser©zwzOctober 24, 2002 Wenzhong Zhao Department of Computer Science The University of Kentucky

Apache DOM ParserOctober 24, 2002©zwz Overview  org.w3c.dom –Node Document Element Attr Text –NodeList –NamedNodeMap  org.apache.xerces.parsers –DOMParser  Sample Code Segment  Xerces Parser Info

Apache DOM ParserOctober 24, 2002©zwz Overview This is a test “is” “This” “a test” id= “1”

Apache DOM ParserOctober 24, 2002©zwz Overview “is” “This” “a test” id= “1” Document

Apache DOM ParserOctober 24, 2002©zwz Overview “is” “This” “a test” id= “1” Document Element

Apache DOM ParserOctober 24, 2002©zwz Overview “is” “This” “a test” id= “1” Document Element Attr Text

Apache DOM ParserOctober 24, 2002©zwz DOM Interface  Represents XML documents as objects –Extract information –Manipulate XML documents  A set of Interfaces –Defined by w3c –Platform and language-neutral –Must be implemented by classes which contain actual data –The DOM parser: responsible for providing those implementation classes

Apache DOM ParserOctober 24, 2002©zwz DOM Interface Hierarchy  Node –Attr –CharacterData Comment Text –CDATASection –Document –DocumentFragment –DocumentType –Element –Entity –EntityReference –Notation –ProcessingInstruction  DOMImplementation  NamedNodeMap  NodeList

Apache DOM ParserOctober 24, 2002©zwz Interface Node  Represents a single node  The primary datatype for the entire DOM  Methods defined here are available for all sub-interfaces  Methods –Public NodeList getChildNodes() –Public Node getFirstChild() –Public Node getNextSibling() –Public Node getParentNode() –Public NamedNodeMap getAttributes()

Apache DOM ParserOctober 24, 2002©zwz Interface Node (cont’) –Public String getNodeName() –Public String getNodeValue() –Public short getNodeType() –Public Node appendChild(Node newChild) throws DOMException –Public Node removeChild(Node oldChild) throws DOMException

Apache DOM ParserOctober 24, 2002©zwz Interface Document  Represents an entire XML document  Methods –Public Element getDocumentElement() Returns the root element of the document –Public NodeList getElementsByTagName(String tag) Returns a list of nodes with the specified tag name In the order of a preorder traversal of the document

Apache DOM ParserOctober 24, 2002©zwz Interface Element  Represents an element in a document  Methods –Public NodeList getElementsByTagName(String tag) Returns a list of nodes with the specified tag name In the order of a preorder traversal of the document –Public String getTagName() –Public Attr getAttributeNode()

Apache DOM ParserOctober 24, 2002©zwz Interface Attr  Represents an attribute in an Element object  Methods –Public String getName() –Public String getValue() –Public void setValue(String value) throws DOMException

Apache DOM ParserOctober 24, 2002©zwz Interface Text  Represents the textual content of an Element or Attr  Methods –Public String getData() throws DOMException –Public void setData(String data) throws DOMException –Public int getLength() Returns the size of the Text node

Apache DOM ParserOctober 24, 2002©zwz Interface NodeList  Represents a collection of nodes –an ordered collection  Methods –Public Node item(int index) Returns the node with the specified index Note: index starts with 0 –Public int getLength() Returns the size of the node list

Apache DOM ParserOctober 24, 2002©zwz Interface NamedNodeMap  Represents a collection of nodes –Can be accessed by name –Not maintained in any particular order  Methods –Public Node getNamedItem(String name) Returns the node with the specified name –Public Node item(int index) Returns the node with the specified ordinal index Note: index starts with 0 –Public int getLength() Returns the size of the node collection –Public void setNamedItem(Node newNode) throws DOMException

Apache DOM ParserOctober 24, 2002©zwz Class DOMParser  A software library (or software package) –Provides clear APIs for client applications to manipulate XML documents.  Is tree-based –Produces a w3c DOM tree in memory which is called a Document object.  Client applications access or modify the information stored in the original XML document by –Invoking methods on the Document object –Invoking methods on other objects it contains.  Vendors: –Apache, Oracle, IBM, Microsoft, Sun, Tibco

Apache DOM ParserOctober 24, 2002©zwz DOMParser (cont’)  Constructor: –Public DOMParser() Use DTD/Schema parser configuration  Methods –Public void parse(String systemId) throws SAXException and IOException Build a DOM tree if successful –Public void parse(InputSource is) throws SAXException and IOException Build a DOM tree if successful –Public Document getDocument() Return a Document object

Apache DOM ParserOctober 24, 2002©zwz DOMParser (cont’) –void setFeature(String featureId, boolean state) Throws SAXNotRecognizedException and SAXNotSupportedException Set the state of the feature in the SAX2 parser –void setProperty(String propertyId, Object value) Throws SAXNotRecognizedException and SAXNotSupportedException Set the value of the property in the SAX2 parser schemaLocationhttp://apache.org/xml/properties/schema/external- schemaLocation

Apache DOM ParserOctober 24, 2002©zwz DOMParser (cont’) –Protected void setValidation(boolean validation) Throws SAXNotRecognizedException and SAXNotSupportedException Set whether the parser validates (by default, against DTD) Equivalent to setFeature() –Feature ID: –Protected void setValidationSchema(boolean schema) Throws SAXNotRecognizedException and SAXNotSupportedException Set schema support on/off Equivalent to setFeature() –Feature ID:

Apache DOM ParserOctober 24, 2002©zwz Sample Code Segment DOMParser parser = new DOMParser();// Create a Xerces DOM Parser parser.setFeature(“ true); // Set the feature for validation against DTD /* Prepare the SystemId for the XML document here … */ parser.parse(SystemId);//Parse the input XML document Document doc = parser.getDocument();//Obtain the Document object Element root = doc.getDocumentElement();//Obtain the root element NodeList nl = doc.getElementsByTagName(“person");//Get the Node List by name int len = nl.getLength();//Get the length of the NodeList for (int i = 0; i < len; i++) { Node node = (Node) nl.item(i);//Get the Node by index if (node.hasChildNodes()) { //Do something for this Node’s children Node firstChild = (Node) node.getFirstChild(); … }

Apache DOM ParserOctober 24, 2002©zwz Xerces Parser Info  Apache Xerces Parser API:  Feature IDs:  Property IDs:  Location for Xerces Parser in cslab machine: /usr/local/xml-xerces2  Be sure to include the following packages in your java source: –org.apache.xerces.parsers.DOMParser –org.xml.sax.helpers.* –org.xml.sax.* –org.w3c.dom.* –Others maybe