Internet Technologies1 Java and XML (DOM and SAX) Some of the material for these slides came from...

Internet Technologies 1

Java and XML (DOM and SAX)

Some of the material for these slides came from the followingsources:

“XML a Manager’s Guide” by Kevin Dick “The XML Companion” by Bradley Java Documentation from Sun Microsystems “XML and Java” by Maruyama, Tamura and Uramoto

On and Off the internet…


Java and XML (DOM and SAX)

• Parser Operations with DOM and SAX overview • Processing XML with SAX (locally and on the internet)

• Processing XML with DOM (locally and on the internet)


FixedFloatSwap.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap SYSTEM "FixedFloatSwap.dtd"><FixedFloatSwap> <Notional>100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments></FixedFloatSwap>


FixedFloatSwap.dtd

<?xml version="1.0" encoding="utf-8"?><!ELEMENT FixedFloatSwap (Notional, Fixed_Rate, NumYears, NumPayments ) ><!ELEMENT Notional (#PCDATA) ><!ELEMENT Fixed_Rate (#PCDATA) ><!ELEMENT NumYears (#PCDATA) ><!ELEMENT NumPayments (#PCDATA) >


Operation of a Tree-based Parser

Tree-BasedParser

ApplicationLogic

Document Tree

Valid

XML DTD

XML Document


Tree Benefits

• Some data preparation tasks require early

access to data that is further along in the

document (e.g. we wish to extract titles to build a table of contents)

• New tree construction is easier (e.g. XSLT works from a tree to convert FpML to WML)


Operation of an Event Based Parser

Event-BasedParser

ApplicationLogic

Valid

XML DTD

XML Document


Operation of an Event Based Parser

Event-BasedParser

ApplicationLogic

Valid

XML DTD

XML Document

public void startDocument ()public void endDocument ()public void startElement (…))public void endElement (…)public void characters (…))

public void error(SAXParseException e) throws SAXException { System.out.println("\n\n--Invalid document ---" + e); }


Event-Driven Benefits

• We do not need the memory required for trees

• Parsing can be done faster with no tree construction going on


Some of the XML API’s in JDK1.4


There are more in JWSDP


Important SAX interfaces and classes (JDK1.4)

class InputSource -- A single input source for an XML entity

interface XMLReader -- defines parser behavior (implemented by Xerces’ SAXParser and others) Four core SAX2 handler interfaces:

•EntityResolver •DTDHandler •ContentHandler •ErrorHandler

Implemented byclass DefaultHandler


Processing XML with SAX

interface XMLReader -- defines parser behavior (implemented by Xerces’ SAXParser) XMLReader is the interface that an XML parser's SAX2 driver must implement. This interface allows an application to set and query features and properties in the parser, to register event handlers for document processing, and to initiate a document parse.


Processing XML with SAX

• We will look at the following interfaces and classes and then study an example

interface ContentHandler -- reports on document events interface ErrorHandler – reports on validity errors class DefaultHandler – implements both of the above plus two others


public interface ContentHandler

Receive notification of general document events.

This is the main interface that most SAX applications implement: if the application needs to be informed of basic parsing events, it implements this interface andregisters an instance with the SAX parser using the setContentHandler method.

The parser uses the instance to report basic document-related events like thestart and end of elements and character data.


void characters(…) Receive notification of character data.void endDocument(…) Receive notification of the end of a document.void endElement(…) Receive notification of the end of an element.void startDocument(…) Receive notification of the beginning of a document. void startElement(…) Receive notification of the beginning of an element.

Some methods from the ContentHandler Interface


public interface ErrorHandler

Basic interface for SAX error handlers.

If a SAX application needs to implement customized error handling, it must implement this interface and then register an instance with the SAX parser.The parser will then report all errors and warnings through this interface.

For XML processing errors, a SAX driver must use this interface instead ofthrowing an exception: it is up to the application to decide whether to throwan exception for different types of errors and warnings. Note, however,that there is no requirement that the parser continue to provide useful informationafter a call to fatalError.


public interface ErrorHandler

Some methods are:

void error(SAXParseException exception) Receive notification of a recoverable error.void fatalError(SAXParseException exception) Receive notification of a non-recoverable error.void warning(SAXParseException exception) Receive notification of a warning.


public class DefaultHandlerextends java.lang.Objectimplements EntityResolver, DTDHandler, ContentHandler, ErrorHandler

Default base class for handlers.

This class implements the default behavior for four SAX interfaces: EntityResolver, DTDHandler, ContentHandler, and ErrorHandler.


<?xml version="1.0" encoding="utf-8"?><!ELEMENT FixedFloatSwap ( Bank, Notional, Fixed_Rate, NumYears, NumPayments ) ><!ELEMENT Bank (#PCDATA)><!ELEMENT Notional (#PCDATA)><!ATTLIST Notional currency (dollars | pounds) #REQUIRED><!ELEMENT Fixed_Rate (#PCDATA) ><!ELEMENT NumYears (#PCDATA) ><!ELEMENT NumPayments (#PCDATA) >

FixedFloatSwap.dtd

Input DTD


<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap SYSTEM "FixedFloatSwap.dtd" [<!ENTITY bankname "Pittsburgh National Corporation"> ]> <FixedFloatSwap> <Bank>&bankname;</Bank> <Notional currency = "pounds">100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments> </FixedFloatSwap>

FixedFloatSwap.xml

Input XML


Processing// NotifyStr.java// Adapted from XML and Java by Maruyama, Tamura and // Uramoto

import java.io.*;

import org.xml.sax.*;import org.xml.sax.helpers.*;

import javax.xml.parsers.*;

public class NotifyStr extends DefaultHandler{


public static void main (String argv []) throws IOException, SAXException { if (argv.length != 1) { System.err.println ("Usage: java NotifyStr filename.xml"); System.exit (1); }

XMLReader reader = XMLReaderFactory.createXMLReader( "org.apache.xerces.parsers.SAXParser");

InputSource inputSource = new InputSource(argv[0]); reader.setContentHandler(new NotifyStr()); reader.parse(inputSource); System.exit (0); }


public NotifyStr() {}

public void startDocument() throws SAXException {

System.out.println("startDocument called:"); }

public void endDocument() throws SAXException {

System.out.println("endDocument called:");

}


public void startElement(String namespaceURI, String localName, String qName, Attributes aMap) throws SAXException {

System.out.println("startElement called: element name =" + localName); // examine the attributes for(int i = 0; i < aMap.getLength(); i++) {

String attName = aMap.getLocalName(i); String type = aMap.getType(i); String value = aMap.getValue(i); System.out.println(" attribute name = " + attName + " type = " + type + " value = " + value); } }

<pre:LocalPart>Qualified Name


public void characters(char[] ch, int start, int length) throws SAXException {

// build String from char array String dataFound = new String(ch,start,length); System.out.println("characters called:" + dataFound);

}

}


C:\McCarthy\www\95-733\examples\sax>java NotifyStr FixedFloatSwap.xmlstartDocument called:startElement called: element name =FixedFloatSwapstartElement called: element name =Bankcharacters called:Pittsburgh National CorporationstartElement called: element name =Notional attribute name = currency type = dollars|pounds value = poundscharacters called:100startElement called: element name =Fixed_Ratecharacters called:5startElement called: element name =NumYearscharacters called:3startElement called: element name =NumPaymentscharacters called:6endDocument called: Output


Accessing the swap from the internet

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap [<!ENTITY bankname "Pittsburgh National Corporation"> ]> <FixedFloatSwap> <Bank>&bankname;</Bank> <Notional currency = "pounds">100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments> </FixedFloatSwap>

Saved under webapps/sax/fpml/FixedFloatSwap.xml


The Deployment Descriptor

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2.2.dtd"> <web-app> <servlet> <servlet-name>SaxExample</servlet-name> <servlet-class>GetXML</servlet-class> </servlet> <servlet-mapping> <servlet-name>SaxExample</servlet-name> <url-pattern>/GetXML/*</url-pattern> </servlet-mapping></web-app>

webapps/sax/WEB-INF/web.xml


// This servlet file is stored under Tomcat in // webapps/sax/WEB-INF/classes/GetXML.java// This servlet returns a user selected xml file from // webapps/sax/fpml directory// and returns it as a string to the client.

import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.http.*;

public class GetXML extends HttpServlet {

// Servlet


public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {

System.out.println("doGet called with " + req.getPathInfo()); String theData = ""; String extraPath = req.getPathInfo(); extraPath = extraPath.substring(1); // read the file try { // open file and create a DataInputStream FileInputStream theFile =

new FileInputStream( "D:\\jakarta-tomcat-4.0.1\\webapps\\sax\\fpml\\“ +extraPath);


InputStreamReader is = new InputStreamReader(theFile); BufferedReader br = new BufferedReader(is);

// read the file into the string theData String thisLine; while((thisLine = br.readLine()) != null) { theData += thisLine + "\n"; } } catch(Exception e) { System.err.println("Error " + e); }


PrintWriter out = res.getWriter();

out.write(theData); System.out.println("Wrote document to client"); //System.out.println(theData); out.close(); }

}


// TomcatNotifyStr.java// Adapted from XML and Java by Maruyama, Tamura and Uramoto

import java.io.*;import org.xml.sax.*;import org.xml.sax.helpers.*;import javax.xml.parsers.*;

public class TomcatNotifyStr extends DefaultHandler{ public static void main (String argv []) throws IOException, SAXException { if (argv.length != 1) { System.err.println ("Usage: java NotifyStr filename.xml"); System.exit (1); }

// Client


XMLReader reader = XMLReaderFactory.createXMLReader( "org.apache.xerces.parsers.SAXParser");

String serverString = "http://localhost:8080/sax/GetXML/"; String fileName = argv[0];

InputSource inputSource = new InputSource(serverString + fileName); reader.setContentHandler(new TomcatNotifyStr());

reader.parse(inputSource); System.exit (0); }


public TomcatNotifyStr() {}

public void startDocument() throws SAXException {

System.out.println("startDocument called:"); }

public void endDocument() throws SAXException {

System.out.println("endDocument called:");

}


public void startElement(String namespaceURI, String localName, String qName, Attributes aMap) throws SAXException {

System.out.println("startElement called: element name =" + localName); // examine the attributes for(int i = 0; i < aMap.getLength(); i++) {

String attName = aMap.getLocalName(i); String type = aMap.getType(i); String value = aMap.getValue(i); System.out.println(" attribute name = " + attName + " type = " + type + " value = " + value); } }


public void characters(char[] ch, int start, int length) throws SAXException {

// build String from char array String dataFound = new String(ch,start,length); System.out.println("characters called:" + dataFound);

}

}


Being served by the servlet

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap [<!ENTITY bankname "Pittsburgh National Corporation"> ]> <FixedFloatSwap> <Bank>&bankname;</Bank> <Notional currency = "pounds">100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments> </FixedFloatSwap>


C:\McCarthy\www\95-733\examples\sax>java TomcatNotifyStr FixedFloatSwap.xmlstartDocument called:startElement called: element name =FixedFloatSwapcharacters called:

startElement called: element name =Bankcharacters called:Pittsburgh National Corporationcharacters called:

startElement called: element name =Notional attribute name = currency type = CDATA value = poundscharacters called:100characters called:

startElement called: element name =Fixed_Ratecharacters called:5characters called:

startElement called: element name =NumYearscharacters called:3characters called:

startElement called: element name =NumPaymentscharacters called:6characters called:characters called:

endDocument called:

Output


Let’s Add Back the DTD…<?xml version="1.0" encoding="utf-8"?><!ELEMENT FixedFloatSwap ( Bank, Notional, Fixed_Rate, NumYears, NumPayments ) ><!ELEMENT Bank (#PCDATA)><!ELEMENT Notional (#PCDATA)><!ATTLIST Notional currency (dollars | pounds) #REQUIRED><!ELEMENT Fixed_Rate (#PCDATA) ><!ELEMENT NumYears (#PCDATA) ><!ELEMENT NumPayments (#PCDATA) >


And reference the DTD in the XML

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap SYSTEM "FixedFloatSwap.dtd" [<!ENTITY bankname "Pittsburgh National Corporation"> ]> <FixedFloatSwap> <Bank>&bankname;</Bank> <Notional currency = "pounds">100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments> </FixedFloatSwap>


We get new output

How many times did wevisit the servlet?Twice. Once for the xmland a second time for the DTD.

C:\McCarthy\www\95-733\examples\sax>java TomcatNotifyStr FixedFloatSwap.xmlstartDocument called:startElement called: element name =FixedFloatSwapstartElement called: element name =Bankcharacters called:Pittsburgh National CorporationstartElement called: element name =Notional attribute name = currency type = dollars|pounds value = poundscharacters called:100startElement called: element name =Fixed_Ratecharacters called:5startElement called: element name =NumYearscharacters called:3startElement called: element name =NumPaymentscharacters called:6endDocument called:


We don’t have to go through a servlet…Tomcat can send the

files

String serverString = "http://localhost:8080/sax/fpml/"; String fileName = argv[0];

InputSource is = new InputSource(serverString + fileName);

But the servlet illustrates that the XML data can be generated dynamically.


The InputSource Class

The SAX and DOM parsers need XML input. The “output”produced by these parsers amounts to a series of method calls(SAX) or an application programmer interface to the tree (DOM).

An InputSource object can be used to provide input to theparser.

InputSurce SAX or DOM

Tree

Eventsapplication

So, how do we build an InputSource object?


Some InputSource constructors:

InputSource(String pathToFileOrAURL); InputSource(InputStream byteStream); // bytes InputStream(Reader characterStream); // Characters

For example: String text = “<a>some xml</a>”; StringReader sr = new StringReader(text); InputSource is = new InputSource(sr); : myParser.parse(is);

Pass The InputSource Class to the Parser


But what about the DTD?

public interface EntityResolver

Basic interface for resolving entities.

If a SAX application needs to implement customized handling for external entities, it must implement this interface and registeran instance with the SAX parser using the parser'ssetEntityResolver method.

The parser will then allow the application to intercept any externalentities (including the external DTD subset and external parameterentities, if any) before including them.


EntityResolver

public InputSource resolveEntity(String publicId, String systemId) {

// Add this method to the client above. The systemId String // holds the path to the dtd as specified in the xml document. // We could now build an InputStream object from a different // systemID and return this new InputStream. Or simply return null // and let the parser resolve the external entity. System.out.println("Attempting to resolve" + "Public id :" + publicId + "System id :" + systemId); return null;

}


• The following examples were tested using Sun’s JAXP (JDK1.4)

Processing XML with DOM


XML DOM

• The World Wide Web Consortium’s Document Object Model

•Provides a common vocabulary to use in manipulating XML documents.

• May be used from C, Java, Perl, Python, or VB

• Things may be quite different “under the hood”.

• The interface to the document will be the same.


<?xml version = "1.0" ?><!DOCTYPE TopCat SYSTEM "cats.dtd"> <TopCat> I am The Cat in The Hat <LittleCatA> I am Little Cat A </LittleCatA> <LittleCatB> I am Little Cat B <LittleCatC> I am Little Cat C </LittleCatC> </LittleCatB> <LittleCatD/></TopCat>

The XML File “cats.xml”


Little cat A

Little cat B

I am little cat B

topcat

I am the cat

in the hat

Little cat D

Little Cat C

I am littlecat C

I am littlecat A

document

XML doc

doctype element

text element element element

text text

text

element

DOM

Called the Document Element


Agreement.xml



document

XML doc

doctype

FixedFloatSwap

Notional

FixedRate NumYears NumPayments

All of these nodes implement the Node interface

100 5 3 6


Operation of a Tree-based Parser

Tree-BasedParser

ApplicationLogic

Document Tree

Valid

XML DTD

XML Document


Some DOM Documentation from JavaSoft


The Node Interface

• The Node interface is the primary datatype for the entire Document Object Model.

• It represents a single node in the document tree.

• While all objects implementing the Node interface expose methods for dealing with children, not all objects implementing the Node interface may have children.

• For example, Text nodes may not have children.


Properties

• All Nodes have properties.

• Not all properties are needed by all types of nodes.

• The attribute property is an important part of the Element node but is null for the Text nodes.

• We access the properties through methods…


Some Methods of Node

Example Methods are:

String getNodeName() – depends on the Node type

if Element node return tag name

if Text node return #text




short getNodeType()

Might return a constant like ELEMENT_NODE or TEXT_NODE or …




String getNodeValue()

if the Node is an Element Node then return ‘null’

if the Node is a Text Node then return a String representing that text.




Node getParentNode()

returns a reference to the parent




public Node getFirstChild()

Returns the value of the firstChild property.




public NodeList getChildNodes()

returns a NodeList object

NodeList is an interface and not a Node.


The NodeList Interface

•The NodeList interface provides the abstraction of an ordered collection of nodes, without defining or constraining how this collection is implemented.

•The items in the NodeList are accessible via an integral index, starting from 0.


There are only two methods of the NodeList Interface

public Node item(int index)

Returns the item at index in the collection. If index is greater than or equal to the number of nodes in the list, this returns null.


There are only two methods of the NodeList Interface

public int getLength()

Returns the value of the length property.


The Element Interface

public interface Elementextends Node

• By far the vast majority of objects (apart from text) that authors encounter when traversing a document are Element nodes.

Inheritance

Nothing prevents us fromextending one interface inorder to create another.

• Those who implement Element just have more promises to keep.




• Some methods in the Element interface

String getAttribute(String name)

Retrieves an attribute value by name.





public String getTagName()

Returns the value of the tagName property.





public NodeList getElementsByTagName(String name)

Returns a NodeList of all descendant elements with a given tag name, in the order in which they would be encountered in a preorder traversal of the Element tree..


The CharacterData Interface

public interface CharacterDataextends Node

The CharacterData interface extends Node with a set of attributes and methods for accessing character data in the DOM. For clarity this set is defined here rather than on each object that usesthese attributes and methods. No DOM objects correspond directly to CharacterData, though Text and others do inherit the interface from it. All offsets in this interface start from 0.


The CharacterData Interface

public interface CharacterDataextends Node

An example method:

public String getData()

Returns the value of the the character data of the node that implements this interface. The Text interface extends CharacterData. public void setData(String data) is also available.


The Document Interface

public interface Documentextends Node

The Document interface represents the entire HTML or XML document. Conceptually, it is the root of the document tree, and provides the primary access to the document's data.



public interface Documentextends Node

Some methods:

public Element getDocumentElement()

Returns the value of the documentElement property. This is a convenience attribute that allows direct access to the child node that is the root element of the document. For HTML documents, this is the element with the tagName "HTML".



Some methods:

public NodeList getElementsByTagName(String tagname)

Returns a NodeList of all the Elements with a given tag name in the order in which the would be encountered in a preorder traversal of the Document tree. Parameters: tagname - The name of the tag to match on. The special value "*" matches all tags. Returns: A new NodeList object containing all the matched Elements.


FixedFloatSwap.xml



document

XML doc

doctype

FixedFloatSwap

Notional


100 5 3 6

FixedFloatSwap.xml


An Example

import java.io.File;import org.w3c.dom.*;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.DocumentBuilder;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;

Process a local file


public class Simulator3 { public static void main(String argv[]) { Document doc; if(argv.length != 1 ) {

System.err.println("usage: java Simulator3 documentname"); System.exit(1);

} try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();


doc = docBuilder.parse(new File(argv[0])); Element top = doc.getDocumentElement(); NodeList elementList = top.getElementsByTagName("*"); int listLength = elementList.getLength();

for(int i = 0; i < listLength; i++) { Element e = (Element)elementList.item(i); System.out.print(e.getNodeName()); Text t = (Text)e.getFirstChild(); System.out.println(t.getNodeValue());

}


} catch(SAXParseException err) { System.out.println("Parsing error" + ", line " + err.getLineNumber() + ", URI " + err.getSystemId()); System.out.println(" " + err.getMessage()); } catch(SAXException e) { Exception x = e.getException(); ((x == null) ? e : x).printStackTrace(); } catch (Throwable t) { t.printStackTrace(); } System.exit(0); }}


FixedFloatSwap.xml <?xml version="1.0" encoding="UTF-8"?><!DOCTYPE FixedFloatSwap SYSTEM "FixedFloatSwap.dtd"><FixedFloatSwap> <Notional>100</Notional> <Fixed_Rate>5</Fixed_Rate> <NumYears>3</NumYears> <NumPayments>6</NumPayments></FixedFloatSwap>


Output

Notional100Fixed_Rate5NumYears3NumPayments6


Read-Process-Write XML

<?xml version="1.0"?><GradeBook> <Student> <Score>100</Score> </Student></GradeBook>

MyGradeBook.xml


ChangeGrade.java

import java.io.File;import org.w3c.dom.*;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.DocumentBuilder;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;import org.apache.xml.serialize.OutputFormat;import org.apache.xml.serialize.XMLSerializer;import java.io.ByteArrayOutputStream;


public class ChangeGrade { public static void main(String argv[]) { Document doc;

if(argv.length != 2 ) { System.err.println(

"usage: java ChangeGrade GradebookName newScore"); System.exit(1);

} try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();


// read and parse the document and build the Dom tree doc = docBuilder.parse(new File(argv[0]));

// get the score String newScore = (new Integer(argv[1])).toString();

// get document element

Element top = doc.getDocumentElement();

// get and change score element NodeList anotherList = top.getElementsByTagName("Score"); Element score = (Element)anotherList.item(0); Text t = (Text)score.getFirstChild();

t.setNodeValue(newScore);


// write the document to a file OutputFormat formatter = new OutputFormat(); XMLSerializer serializer = new XMLSerializer(System.out, formatter); serializer.serialize(doc);

// write the document to a byte array ByteArrayOutputStream baos = new ByteArrayOutputStream(); serializer = new XMLSerializer(baos, formatter); serializer.serialize(doc);

// fill an array of bytes byte[] bytes = baos.toByteArray();


// convert to string String s = baos.toString(); System.out.println("As a String"); System.out.println(s); } catch(SAXParseException err) { System.out.println("Parsing error" + ", line " + err.getLineNumber() + ", URI " + err.getSystemId()); System.out.println(" " + err.getMessage()); } catch(SAXException e) { Exception x = e.getException(); ((x == null) ? e : x).printStackTrace(); } catch (Throwable t) { t.printStackTrace(); } System.exit(0); }}


D:\McCarthy\www\95-733\examples\dom>java ChangeGrade MyGradeBook.xml 34<?xml version="1.0" encoding="UTF-8"?><GradeBook> <Student> <Score>34</Score> </Student> </GradeBook>As a String<?xml version="1.0" encoding="UTF-8"?><GradeBook> <Student> <Score>34</Score> </Student> </GradeBook>


Using the InputSource classD:\McCarthy\www\95-733\examples\dom\internetexample>tree /fDirectory PATH listingVolume serial number is 0012FC94 486D:D392D:.│ build.properties│ build.xml├───build│ │ MyGradeBook.xml│ ││ └───WEB-INF│ ├───classes│ └───lib├───src└───web MyGradeBook.xml


Using the InputSource Class

import java.io.File;import org.w3c.dom.*;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.DocumentBuilder;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;import org.apache.xml.serialize.OutputFormat;import org.apache.xml.serialize.XMLSerializer;import java.io.ByteArrayOutputStream;import org.xml.sax.InputSource;


public class ReadGradesFromInternet { public static void main(String argv[]) { Document doc;

try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();

InputSource inputSource = new InputSource( "http://localhost:8080/Grades/MyGradeBook.xml");

// read and parse the document and build the Dom tree doc = docBuilder.parse(inputSource);


// write the document to a file OutputFormat formatter = new OutputFormat(); XMLSerializer serializer = new XMLSerializer(

System.out, formatter); serializer.serialize(doc);

} catch(SAXParseException err) { System.out.println("Parsing error" + ", line " + err.getLineNumber() + ", URI " + err.getSystemId()); System.out.println(" " + err.getMessage()); } catch(SAXException e) { Exception x = e.getException(); ((x == null) ? e : x).printStackTrace(); } catch (Throwable t) { t.printStackTrace(); } System.exit(0); }}


D:\McCarthy\www\95-733\examples\dom>java ReadGradesFromInternet<?xml version="1.0" encoding="UTF-8"?><GradeBook> <Student> <Score>100</Score> </Student> </GradeBook>


Example - A TreePrint Classimport org.w3c.dom.*;

public class TreePrinter {

private Document doc; private int currentIndent;

public TreePrinter(Document d) { currentIndent = 2; doc = d; }

public void print() {

privatePrint(doc,currentIndent);

}}


document

XML doc

doctype

FixedFloatSwap

Notional


100 5 3 6

FixedFloatSwap.xml


public void privatePrint(Node n, int indent) { for(int i = 0; i < indent; i++) System.out.print(" ");

switch( n.getNodeType()) {

// Print information as each node type is encountered

case n.DOCUMENT_NODE : System.out.println(n.getNodeName() + "...Document Node"); break; case n.ELEMENT_NODE : System.out.println(n.getNodeName() + "...Element Node"); break; case n.TEXT_NODE : System.out.println(n.getNodeName() + "...Text Node"); break; case n.CDATA_SECTION_NODE: System.out.println(n.getNodeName() + "...CDATA Node"); break; case n.PROCESSING_INSTRUCTION_NODE: System.out.println("<?"+n.getNodeName()+"...?>"+ "...PI Node"); break;


case n.COMMENT_NODE: System.out.println("" + "...Comment node"); break; case n.ENTITY_NODE: System.out.println("ENTITY "+ n.getNodeName()+ "...Entity Node"); break; case n.ENTITY_REFERENCE_NODE: System.out.println("&"+n.getNodeName()+";" + "...Entity Reference Node"); break; case n.DOCUMENT_TYPE_NODE: System.out.println("DOCTYPE"+n.getNodeName()+ "...Document Type Node"); break; default: System.out.println("?" + n.getNodeName()); } Node child = n.getFirstChild(); while(child != null) { privatePrint(child, indent+currentIndent); child = child.getNextSibling(); } } }


OutputC:\McCarthy\www\Financial Engineering\FixedFloatSwap>java Simulator6No Problems found #document...Document Node DOCTYPEFixedFloatSwap...Document Type Node FixedFloatSwap...Element Node #text...Text Node Notional...Element Node #text...Text Node #text...Text Node Fixed_Rate...Element Node #text...Text Node #text...Text Node NumYears...Element Node #text...Text Node #text...Text Node NumPayments...Element Node #text...Text Node #text...Text Node


Building a DOM Tree From Scratch

<?xml version="1.0" encoding="UTF-8"?>

<GradeBook> <Student> <Score>100</Score> </Student></GradeBook>

Let’s create this filefrom within a javaprogram.

MyGradeBook.xml


GOAL

C:\McCarthy\www\95-733\examples\dom>java DomExample

C:\McCarthy\www\95-733\examples\dom>type MyGradeBook.xml<?xml version="1.0"?><GradeBook><Student><Score>100</Score></Student></GradeBook>


// DomExample.java// Building an xml document from scratch

import java.io.*;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.ParserConfigurationException;import org.w3c.dom.*;import org.apache.xml.serialize.XMLSerializer; // not standardimport org.apache.xml.serialize.OutputFormat; // not standard


public class DomExample {

private Document document; public DomExample () {

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); try {

DocumentBuilder builder = factory.newDocumentBuilder();

document = builder.newDocument(); }

catch (Throwable t) { t.printStackTrace ();

}


// Ask the Document object for various types // of nodes and // add them to the tree.

Element root = document.createElement("GradeBook"); document.appendChild(root); Element student = document.createElement("Student"); root.appendChild(student); Element score = document.createElement("Score"); student.appendChild(score); Text value = document.createTextNode("100"); score.appendChild(value);


// Write the Document to disk using Xerces. try {

FileOutputStream fos = new FileOutputStream( "MyGradeBook.xml"); XMLSerializer xmlWriter = new XMLSerializer(fos, null); xmlWriter.serialize(document); } catch(IOException ioe) { ioe.printStackTrace(); } }


public static void main(String a[]) {

DomExample tree = new DomExample(); }}

Date post:	22-Dec-2015
Category:	Documents
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Internet Technologies1 Java and XML (DOM and SAX) Some of the material for these slides came from...

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