1 xmlxml and.netnoea / pqc 2005 (rev. fen 2007) xml and the.net framework heavily inspired by:...

1 XML XML and .NET NOEA / PQC 2005

(rev. FEN 2007)

XML and the .NET framework

• Heavily inspired by:Support WebCast: Programming XML in the Microsoft .NET Framework Part I

• XML related .NET Framework namespaces • Introduction to XML parsing models in the .NET Framework• DOM parsing in .NET the Framework• Pull model XML parsing in the .NET Framework• Generation of XML in the .NET Framework• Validating XML documents• XSLT transformations• XPath queries


(rev. FEN 2007)

Basic .NET Framework XML Namespaces

• System.Xml– Contains classes that offers standard support for xml– Supported W3C XML standards:

• XML 1.0 og XML namespaces• XML schemas• XPath• XSLT• DOM level 2 core• SOAP 1.1 (used for fx. webservices)


(rev. FEN 2007)

Basic .NET Framework XML Namespaces

• System.Xml.Xsl– Contains classes for XSLT transformations

• System.Xml.XPath– Contains classes for XPath queries

• System.Xml.Schema– Contains classes for standards-based support of W3C XML

schemas• System.Xml.Serialization

– Contains classes used for serialization and deserialization of .NET Framework objects to / from XML


(rev. FEN 2007)

XML Parsing Models

• XML parsing models :– DOM model (DOM = Document Object Model)– Forward only pull model parsing– Forward only push model parsing (SAX)

Event based. The model is implemented in Java, but not in .NET

Stores the tree as a data structure and traverse it e.g. with

XPATH

Traverse the XML-document and fires

events for each node

Traverse the XML-document with a cursor and fetch

each node


(rev. FEN 2007)

XML-based I/O

• XML-based I/O performed using a streaming interface suite– Models a stream of logical XML nodes (think Infoset)– Streaming done in pull-mode (read) and push-mode (write)– Built-in streaming adapters use System.IO.Stream– Abstract interfaces allow you to provide your own XML

providers/consumers


(rev. FEN 2007)

<s:Envelope xmlns:s='...'> <s:Body> <m:Add xmlns:m='urn:math'> <x>33.3</x> <y>66.6</y> </m:Add> </s:Body></s:Envelope>

Document

Element: Envelope

Element: Add

Element: x

Text: 33.3

EndElement:x

XmlTextReader

XmlReader

XmlTextWriter

XmlWriter

Element: y

Element: Body

Text: 66.6

Working with a Stream of Nodes


(rev. FEN 2007)

Non-Cached Parsing

• XmlReader and XmlWriter are abstract classes for reading and writing xml documents.

• The XmlReader is a “pull” model parser. • MS says: The Pull model has several advances compared to the

SAX “push” model: state management, selective processing, layering, etc.

• Sun & IBM can surely mention some advances in the SAX model Could be multithreading

• Concrete implementation:• XmlTextReader - offers non-cached, forward-only, read-only

access• XmlTextWriter – offers a fast non-cached forward-only way of

generating XML


(rev. FEN 2007)

XmlReader

• XmlReader models reading a stream of nodes– XmlReader is an abstract class (somewhat interface-like)– Pull-model pushes complexity into provider implementation– Manages a forward/read-only cursor over a stream of nodes– Provides properties for inspecting current node– Nodes are processed in document order (depth-first traversal)


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Moving the Cursor

• Read is the only method that advances the cursor

while (reader.Read()){ // process current node here}

cursor cursor’

Read


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Read Helpers

• XmlReader provides several helpers that simplify Read– MoveToContent facilitates dealing with non-content nodes– Skip moves past the end of the current node– ReadStartElement simplifies validation code by skipping non-content

nodes and checking current node before moving– ReadEndElement checks that current node is EndElement before

moving– ReadElementString reads text within text-only elements and

advances the cursor past EndElement


(rev. FEN 2007)

Example

private static void XmlReaderEx(){ XmlReader r = new XmlTextReader("author.xml"); string id, first, last, phone; r.ReadStartElement("author", "urn:authors"); r.ReadStartElement("name"); first = r.ReadElementString("first"); last = r.ReadElementString("last"); r.ReadEndElement(); //name phone = r.ReadElementString("phone"); r.ReadEndElement(); //a:author r.Close(); Console.WriteLine("Name: {0} {1}\nTelf: {2}", first, last, phone); Console.ReadLine();}

<?xml version="1.0" encoding="utf-8" ?><x:author xmlns:x="urn:authors" id="333-33-3333"> <name> <first>Bob</first> <last>Smith</last> </name> <phone>333-3333</phone></x:author>


(rev. FEN 2007)

Reading Attribute Nodes

• XmlReader handles attributes differently– Attribute nodes are not part of sequential stream– Cursor must be on the element to process attributes– GetAttribute/Item retrieve value by name/index– MoveToAttribute moves to attribute by name/index– MoveToElement returns to owner element node– MoveToFirstAttribute/MoveToNextAttribute to iterate

cursor

attributes


(rev. FEN 2007)

Example

private static void MoveToContentEx(){ XmlReader r = new XmlTextReader("author.xml"); string id, first, last, phone; r.MoveToContent(); // should be on author id = r["id"]; r.ReadStartElement("author", "urn:authors"); r.ReadStartElement("name"); first = r.ReadElementString("first"); last = r.ReadElementString("last"); r.ReadEndElement(); //name phone = r.ReadElementString("phone"); r.ReadEndElement(); //a:author r.Close(); Console.WriteLine("Id: {3}\nName: {0} {1} \nTelf: {2}", first, last, phone, id); Console.ReadLine();}



(rev. FEN 2007)

XmlReader Implementations

• Many implementations of XmlReader are possible– XmlTextReader uses a TextReader for I/O over XML 1.0– XmlNodeReader uses an XmlNode as its input source– XmlValidatingReader is a concrete class that provides XML Schema,

XDR, and DTD validation while reading, along with additional type information (more on this later)

– Custom readers can expose your own data as XML


(rev. FEN 2007)

XmlTextReader

XmlReader

XmlNodeReader

XmlReader

YourReader

XmlReader

YourApplication

or Data

XmlNode

XmlNode XmlNode

XmlNode


Document Element: Envelope Element: Add Element: x Text: 33.3Element: Body ...

XmlReader Implementations


(rev. FEN 2007)

XmlTextReader, summary

• Fast way of parsing XML data• Assumes well-formedness• Some properties can be modified before reading:

WhitespaceHandling, XmlResolver, etc.• Offers methods to skip content (more effiecient)

• The MoveToContent method moves directly to the content of an element, and skips fx. comments, attributtes and whitespaces

• The Skip method skips children of the actual node


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The XmlTextReader class

• Able to read data from e.g. File, Stream and TextReader• Key members:

– Methods that begins with “MoveTo” are used for navigating to the actual attributte, element or node

– Methods that begins with “Read” are used for: • Reading the content of XML data, attribute values etc.• Reading various format formatters (Hex, Base64, etc.) and

returning decoded binary bytes– Properties: Encoding, Depth, LineNumber, ReadState, Value, etc.


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Generation of XML in the .NET Framework

• There is to ways in .Net to generate XML:– Non-cached, forward-only streaming (XmlTextWriter)– Creating the document by DOM


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XmlWriter

• XmlWriter models writing a stream of nodes– XmlWriter is an abstract class (somewhat interface-like)– Custom writers inevitable but not as common as readers– Push-mode interface balances complexity between writer

implementation and user


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Writing Nodes

• XmlWriter provides several methods for writing nodes – Sequence of start/end method calls defines structure– Text nodes written via WriteString– Binary data written via WriteBinHex & WriteBase64– WriteElementString helper writes text-only elements– Attribute nodes written via WriteStartAttribute, WriteEndAttribute or

WriteAttributeString methods


(rev. FEN 2007)

public static void WriteAuthorDocument(){ XmlTextWriter tw = new XmlTextWriter(Console.Out); tw.Formatting = Formatting.Indented; tw.WriteStartDocument(); tw.WriteStartElement("x", "author", "urn:authors"); tw.WriteAttributeString("id", id); tw.WriteStartElement("name"); tw.WriteElementString("first", first); tw.WriteElementString("last", last); tw.WriteEndElement(); // name tw.WriteElementString("phone", phone); tw.WriteEndElement(); // author tw.WriteEndDocument();}

Using XmlWriter


(rev. FEN 2007)

XmlTextWriter

XmlWriter

XmlNodeWriter

XmlWriter

YourWriter

XmlWriter

YourApplication

or Data

XmlNode

XmlNode XmlNode

XmlNode

<s:Envelope xmlns:s='...'> <s:Body> <m:AddResponse xmlns:m='urn:math'> <sum>99.9</sum> </m:Add> </s:Body></s:Envelope>

Document Element: Envelope Element: AddResponse Element: sumElement: Body Text: 99.9

XmlWriter Implementations


(rev. FEN 2007)

XmlTextWriter, summary

• Implemented in System.Xml namespace• Inherits from the abtract System.Xml.XmlWriter class• Used for writing XML in a non-cached and forward-only way to fx.

a file or a stream (may be a tcp-socket, directly to the console etc.)


(rev. FEN 2007)

Commonly used properties and method on XmlTextWriter

• Properties• Formatting (should output be indented)• Indentation (How many char is an indent)• QuoteChar (Use " or ' )• IndentChar (Which char is used for the indent, normally

space)• WriteState (Open or Close)

• Methods• WriteXXX metoder – (fx.: WriteStartDocument,

WriteStartElement, WriteAttributeString, etc.)• Close


(rev. FEN 2007)

Normal use of XmlTextWriter

• Create a XmlTextWriter object• Choose formatting of output by setting formatting and

indentation properties • Execute the WriteXXX methods to generate the content of the

XML document• Execute the Close() method


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XML Traversal

• System.Xml provides two traversal APIs– The Document Object Model (DOM)– XPathNavigator cursor-based traversal– Both support XPath and manual traversal


(rev. FEN 2007)

DOM - XmlNode and XmlDocument

• DOM implemented as a hierarchy of concrete classes– XmlNode is at root of hierarchy– XmlDocument supports loading/serializing trees– XmlDocument is generic node factory– XmlNode-hierarchy is extensible


(rev. FEN 2007)

XmlWhitespace

XmlSignificantWhitespace

XmlNode

XmlCharacterData

XmlLinkedNode

XmlComment

XmlCDataSection

XmlText

XmlEntityReference

XmlProcessingInstruction

XmlDocumentType

XmlDeclaration

XmlElement

XmlAttribute

XmlDocumentFragment

XmlEntity

XmlNotation

XmlDocument

XmlNode Hierarchy


(rev. FEN 2007)

Loading/Serializing Documents

• XmlDocument loads and serializes documents– Load method loads from file, TextReader, or XmlReader– Save method saves to a file, TextWriter, or XmlWriter– Load/Save process customized via readers/writers– LoadXml loads the document from a string of XML 1.0– InnerXml/OuterXml serialize node to string of XML 1.0


(rev. FEN 2007)

YourApplication

or Data

XmlTextReader

XmlReader

YourReader

XmlReader

XmlDocument

XmlElement

XmlElementXmlElement

XmlText XmlText

XmlElement

<s:Envelope xmlns:s='...'> <s:Body> <m:Add xmlns:m='urn:math'> <x>33.3</x> <y>66.6</y> </m:Add> </s:Body></s:Envelope> XmlElement

Loading XmlDocument


(rev. FEN 2007)

YourWriter

XmlWriter

XmlTextWriter

XmlWriter

XmlDocument

XmlElement

XmlElementXmlElement

XmlText XmlText

XmlElement

XmlElement

YourApplication

or Data


Serializing XmlDocument


(rev. FEN 2007)

static void Main(string[] args) { XmlDocument doc;

doc = new XmlDocument(); doc.Load("author.xml"); ... // modify author here

// serialize document to file on disk doc.Save("modified-author.xml"); // serialize to an XmlWriter (console) XmlTextWriter wr = new XmlTextWriter(Console.Out); wr.Formatting = Formatting.Indented; doc.Save(wr);

// serialize to string Console.WriteLine(doc.InnerXml);}

Loading and Saving a Document


(rev. FEN 2007)

Navigating DOM Trees

• XmlNode provides properties for navigating DOM trees– Node inspection works like XmlReader – ChildNodes/FirstChild/LastChild access a node's children– NextSibling/PreviousSibling access a node's siblings– ParentNode accesses a node's parent/owner document– OwnerDocument accesses the root XmlDocument node


(rev. FEN 2007)

public void processAuthor1(){ XmlDocument doc = new XmlDocument(); doc.Load("author.xml"); XmlNode first = doc.DocumentElement.FirstChild.FirstChild; XmlNode last = doc.DocumentElement.FirstChild.LastChild; Console.WriteLine("Hello {0} {1}", first.InnerText, last.InnerText);}

Traversing a DOM Tree



(rev. FEN 2007)

Simplifying Traversal with XPath

• XPath can greatly simplify traversal code– XmlNode provides two convenience methods for evaluating XPath

expressions– SelectNodes identifies the set of nodes that match the expression

(returns an XmlNodeList)– SelectSingleNode identifies first XmlNode that matches – Overloads exist to handle namespace support

• Use XmlNamespaceManager to hold namespace bindings


(rev. FEN 2007)

XPath and SelectNodes

public void ProcessAuthor2(){ XmlDocument doc = new XmlDocument(); doc.Load("author.xml"); XmlNamespaceManager ns = new XmlNamespaceManager(doc.NameTable); ns.AddNamespace("x", "urn:authors"); XmlNodeList names = doc.SelectNodes("/x:author/name/*", ns); Console.WriteLine("Hello {0} {1}", names[0].InnerText, names[1].InnerText);}



(rev. FEN 2007)

Summary

• XmlReader is a streaming/pull-model interface for reading• XmlWriter is a streaming/push-model interface for writing• XML traversal can simplify (streaming) code• DOM provides in-memory tree for navigation• DOM tree loaded via XmlReader, serialized via XmlWriter• DOM supports processing XPath queries

View Code:XMLSamplesNew


(rev. FEN 2007)

XPath in .NET

• Related namespaces• System.Xml• System.Xml.XPath

• Most important .NET Framework classes• XmlDocument, XmlNodeList, and XmlNode• XPathDocument• XPathNavigator• XPathNodeIterator• XPathExpression


(rev. FEN 2007)

Execute XPath queries with System.Xml DOM objects

• Common classes: XMLDocument, XMLNodeList, XMLNode

• Load XML dokumentet into an XMLDocument object• Use the selectNodes/selectSingleNode method in the

XmlDocument class to execute the XPath query• Assign the returned nodelist or node to a

XmlNodeList/XmlNode object• Use a XmlNode object to iterate through the

XmlNodeList and handle the result.


(rev. FEN 2007)

System.XML.XPath classes

• XPathDocument– Similar to the XmlDocument DOM object– Optimized for XSLT processing and XPath– Differs from the DOM object by

• Do not maintain node identity• Do not validate the XML document

• XPathNavigator– Used for executing a XPath query on XPathDocument (Select

method)– Used for compiling often used XPath query expressions (Compile

method)– Created with the CreateNavigator() method in the XPathDocument

class


(rev. FEN 2007)

System.XML.XPath classes (2)

• XPathNodeIterator– Offers a read-only cursor style interface for navigating in the result

of a XPath query– Created by executing the Select(<XPath query/expression>)

method on a XPathNavigator object• XPathExpression

– Used for storing a compiled instance of a often used XPath query expression

– Created by calling the Compile(“<XPath query>”) method on a XPathNavigator object

– Can be used as the parameter of the XPathNavigator’s Select method


(rev. FEN 2007)

System.XML.XPath classes (3)

XPathDocument

XPathNavigator

XPathNodeIterator

Load XML

.CreateNavigator()

Select(“<XPath Query>”)

XPathExpression

.Compile(“<XPath query>”)

Select(XPathExpression)

Do While .MoveNext() ‘Process resultsLoop


(rev. FEN 2007)

Eksempel: Navigator

XPathDocument XPathDoc; XPathNavigator XPathNav; XPathExpression XPathExpr; XPathNodeIterator XPNodeIterator;

XPathDoc = new XPathDocument("books.xml"); XPathNav = XPathDoc.CreateNavigator(); XPathExpr = XPathNav.Compile("//x:title[starts-with(.,'XML')]");

XmlNamespaceManager ns = new XmlNamespaceManager(new NameTable()); ns.AddNamespace("x", "http://www.contoso.com/books"); XPathExpr.SetContext(ns);

XPNodeIterator = XPathNav.Select(XPathExpr); if (XPNodeIterator.Count == 0) { Console.WriteLine("No matching nodes were identified for the specified XPath query"); } else { while (XPNodeIterator.MoveNext()) { Console.WriteLine(XPNodeIterator.Current.Value); } }

<?xml version="1.0" encoding="utf-8" ?><bookstore xmlns="http://www.contoso.com/books"> <book genre="autobiography" publicationdate="1981“

--- </book> <book genre="Computer Science" publicationdate="2001“ ISBN="0415205173"> <title>XML Step by Step</title> <author> <name>Michael Young</name> </author> <price>50.00</price> </book></bookstore>


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Execute XSLT transformations in .NET


(rev. FEN 2007)

XSL Transformations

• XSL (Extensible Stylesheet Language) can be seen as 3 parts:• XSLT – XSL transformations• XPath – XML path language• XSL-FO – XSL formatting objects

• XSLT is a language for transforming XML documents to text-based documents

• The transformation process involves 3 documents:• Source XML document• Stylesheet document• Output document – XML, HTML, etc.


(rev. FEN 2007)

XSLT in .NET

• Implemented in the System.Xml.Xsl namespace• Supports the W3C XSLT 1.0 recommendation• Important classes:

• XslTransform – Transforms XML data with a XSLT stylesheet• XsltArgumentList – makes it possible to access parameters and

extension objects from the stylesheet. • XsltException – Returns information of the last exception that is

thrown by the XSL transformation


(rev. FEN 2007)

XSLT architecture in .NET


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XslTransform class

• XSLT stylesheetet shall include the namespace declaration "xmlns:xsl= http://www.w3.org/1999/XSL/Transform"

• Important methods:• Load

– Loads the XSLT stylesheet inclusive xsl:include and xsl:import references

– Overloaded methods can load the stylesheet with XmlReader, XPathNavigator, or a URL

• Transform – Transforms XML data and returns the result– Is overloaded so it can handle different input and output

formats as Stream, File, XMLReader, etc.


(rev. FEN 2007)

Example: XslTransform private static void XslTransform1()private static void XslTransform1() {{ //Transforms the XML data in the input file and outputs the result to an output file//Transforms the XML data in the input file and outputs the result to an output file XslTransform xslt = XslTransform xslt = new new XslTransform();XslTransform(); xslt.Load(xslt.Load("books.xsl");"books.xsl"); xslt.Transform("books.xml", "output.xml");xslt.Transform("books.xml", "output.xml"); // Transforms the XML data in the XPathDocument and outputs the result to an XmlReader// Transforms the XML data in the XPathDocument and outputs the result to an XmlReader String URL = String URL = "http://samples.gotdotnet.com/quickstart/howto/samples/Xml/TransformXml/VB/";"http://samples.gotdotnet.com/quickstart/howto/samples/Xml/TransformXml/VB/"; xslt = xslt = new new XslTransform();XslTransform(); xslt.Load(URL + xslt.Load(URL + "books.xsl");"books.xsl");

XPathDocument doc = XPathDocument doc = new new XPathDocument(URL + XPathDocument(URL + "books.xml");"books.xml"); XmlReader reader = xslt.Transform(doc, XmlReader reader = xslt.Transform(doc, null);null);

//Transforms the XML data in the input file and outputs the result to a stream//Transforms the XML data in the input file and outputs the result to a stream xslt = xslt = new new XslTransform();XslTransform(); xslt.Load(xslt.Load("books.xsl");"books.xsl");

xslt.Transform(xslt.Transform(new new XPathDocument(XPathDocument("books.xml"), "books.xml"), null, null, Console.Out);Console.Out); }}


(rev. FEN 2007)

XsltArgumentList klassen

• Klassen bruges af Transform metoden

• Kan bruges til at tilføje parametre og objekter, der bliver associeret med et namespace

• Vigtigste metoder:

• AddX, GetX, og RemoveX (hvor X = Param eller ExtenstionObject)– Metoder til at tilføje, hente eller fjerne parametre eller

extension objects– Parameter bør være en W3C XPath type; Ellers bliver den

konverteret til Double eller String• Clear

– Fjerner alle parametre og extension objects


(rev. FEN 2007)

Code Sample: XsltArgumentList

// Create the XslCompiledTransform and load the stylesheet.// Create the XslCompiledTransform and load the stylesheet. XslCompiledTransform xslt = XslCompiledTransform xslt = new new XslCompiledTransform();XslCompiledTransform(); xslt.Load(xslt.Load("order.xsl");"order.xsl");

// Create the XsltArgumentList.// Create the XsltArgumentList. XsltArgumentList xslArg = XsltArgumentList xslArg = new new XsltArgumentList();XsltArgumentList();

// Create a parameter which represents the current date and time.// Create a parameter which represents the current date and time. DateTime d = DateTime.Now;DateTime d = DateTime.Now; xslArg.AddParam(xslArg.AddParam("date", "", d.ToString());"date", "", d.ToString());

// Transform the file.// Transform the file. xslt.Transform(xslt.Transform("order.xml", xslArg, "order.xml", xslArg, XmlWriter.Create(XmlWriter.Create("output.xml"));"output.xml")); xslt.Transform("order.xml", xslArg, xslt.Transform("order.xml", xslArg, Console.Out);Console.Out);

(rev. FEN 2007)

Source files

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:param name="date"/> <xsl:template match="/"> <order> <date> <xsl:value-of select="$date"/> </date> <total> <xsl:value-of select="sum(//price)"/> </total> </order> </xsl:template></xsl:stylesheet>

<?xml version="1.0" encoding="utf-8" ?><order> <book ISBN='10-861003-324'> <title>The Handmaid's Tale</title> <price>19.95</price> </book> <cd ISBN='2-3631-4'> <title>Americana</title> <price>16.95</price> </cd></order>


(rev. FEN 2007)

• General:– http://support.microsoft.com/WebCasts– http://www2.msdnaa.net/browse

• XML in .NET, MSDN Magazine, Skonnard– http://msdn.microsoft.com/msdnmag/issues/01/01/xml/default.aspx

• Writing XML Providers in .NET, MSDN Magazine, Skonnard– http://msdn.microsoft.com/msdnmag/issues/01/09/xml/default.aspx

Links


(rev. FEN 2007)

Exercise

• Gennemgå og afprøv eksemplerne i kap.4.7 i Hanspetter• Løs opgave 4.29 og 4.31

Solution:Tasks.zip