Introduction to XML and Web Service

1
Introduction to XML and Web Service

• ISYS 464

2
HTML vs XML

• HTML is a language specifically designed for
  displaying information in browser. It doesnt
  carry information about the structure of the
  content held within its page.
• XML (Extensible MarkUp Language) is a language
  used to represent data in a form that does not
  rely on any particular proprietary technology.
  It uses user-defined tags to give meaningful
  names to data elements. With XML, we separate the
  data content from the data presentation.

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HTML
ltbodygt lth1gtMy Favorite Booklt/h1gt lth1gtISBN -
1-34567-04-01lt/h1gt ltH1gtAuthorslt/H1gt lth3gtJohn
Smithlt/h1gt lth3gtPeter Chenlt/h1gt lth1gtPrice
45.00lt/h1gt lth1gtDescription This is a grerat
booklt/h1gt lt/bodygt
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XML
lt?xml version"1.0" ?gt ltBooksgt ltBookgt ltISBNgt1-3456
7-04-01lt/ISBNgt ltAuthorsgt ltAuthorNamegtJohn
Smithlt/AuthorNamegt ltAuthorNamegtPeter
Chenlt/AuthorNamegt ltAuthorNamegtDavid
Chaolt/AuthorNamegt lt/Authorsgt ltPricegt
45.00lt/Pricegt ltDescriptiongtThis is a grerat
booklt/Descriptiongt lt/Bookgt ltBookgt ltISBNgt1-34567-04
-02lt/ISBNgt ltAuthorsgt ltAuthorNamegtAdam
Smithlt/AuthorNamegt lt/Authorsgt ltPricegt
25.00lt/Pricegt ltDescriptiongtThis is a second
great booklt/Descriptiongt lt/Bookgt lt/Booksgt
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XML Document

• Well-formed documents
• Documents comply with the rules of XML syntax.
• Valid documents
• Documents that are well-formed and comply with a
  XML schema or Document Type Definition (DTD is a
  file containing the rules used to define the
  document).

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Well-Formed Documents

• There is only one root node.
• All elements must have a start tag and an end tag
  (except for an empty element, see example below)
  Elements must be nested correctly.
• If an element has an attribute, the attribute
  value must be quoted.
• An empty element with an attribute
• ltprice US49 /gt
• Note XML is case sensitive.

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XML Documents

• The XML declaration
• lt?xml version1.0 ?gt
• Note xml should be in lower case.
• Namespaces
• Define a namespace xmlnsuri where the Uniform
  Resource Identifier is a unique identifier and is
  often a URL.
• Use a namespace to make a tag unique
• ltnamespace TagNamegt
• Elements
• Each start-tag/end-tag pair, with the data that
  lies between them, is an element.
• Ex. ltAuthorNamegtJohn Smithlt/AuthorNamegt
• The start and end tag must be in the same case.

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• Attributes Elements can have attributes. These
  are values that are passed to the application,
  but not constitute part of the content of the
  element. Attributes are included as part of the
  elements start tag, and values must be enclosed
  in quote marks.
• ltFood healthyyesgtSpinachlt/Foodgt
• ltFood healthyyes tastynogtCarrotlt/Foodgt

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Tree View of XML
Books
Book
Book
ISBN
Authors
Price
Description
ISBN
Authors
Price
Description
Author
Author
Author
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Valid Documents

• Well-formed documents that conform to an XML
  schema.
• XML parsers are programs that are able to
  validate an XML document against schema.

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XML SchemaDefinition of an XML Document

• Namespaces Allow element names to be qualified
  to avoid name collisions.
• Complex and simple types
• Elements that contains other elements are complex
  type.
• Cardinality
• minOccurs 0 for optional element.
• maxOccurs specified number or unbounded
• Compositor
• Sequence defines an ordered sequence of
  subelements.
• Choice defines a choice between several possible
  elements.
• Constraints
• Uniqueness contraint

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Access Support for XML

• File
• Export
• Get External Data

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Style Sheets

• XSL Extensible Stylesheet Language
• Tell the browser how to display the XML document.
• With a style sheet, all of the style rules are
  kept in one file and the source document simply
  links to this file.
• File extension .CSS

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• Browser screen structure
• Page
• Area
• Block Flow Object Taking up the whole line.
• In-Line Flow Object Several in-line objects may
  be on the same line.

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lt?xml version"1.0" ?gt lt?xmlstylesheet
href"books.css" type"text/css"
?gt ltBooksgt ltBookgt ltbtitlegtMy Favorite
Booklt/btitlegt ltISBNgt1-34567-04-01lt/ISBNgt ltAuthors
gt ltAuthorNamegtJohn Smithlt/AuthorNamegt ltAuthorN
amegtPeter Chenlt/AuthorNamegt lt/Authorsgt ltPricegt
45.00lt/Pricegt ltDescriptiongtThis is a grerat
booklt/Descriptiongt lt/Bookgt ltBookgt ltbtitlegtMy
Second Favorite Booklt/btitlegt ltISBNgt1-34567-04-02lt
/ISBNgt ltAuthorsgtAdam Smithlt/Authorsgt ltPricegt
25.00lt/Pricegt ltDescriptiongtThis is a second
great booklt/Descriptiongt lt/Bookgt lt/Booksgt
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btitle displayblock font-family Aerial,
Helvetica font-weight bold font-size
20pt color 9370db text-align
center ISBN displayblock font-family
Aerial, Helvetica font-weight
bold font-size 12pt color
c71585 text-align left Authors display
inline font-family Aerial, Helvetica font-sty
le italic font-size 10pt color
9370db text-align left
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Price displayblock font-family Aerial,
Helvetica font-size 12pt color
ff1010 text-align left Description
displayblock font-family Aerial,
Helvetica font-size 12pt color
ff1010 text-align left
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Demo

• ASPNet/FavoriteBook.htm

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Web Service

• XML Web Service
• Web services are classes that are stored on the
  web which can instantiate and use in both Windows
  and Web applications.

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To Add a New Web Service

• Website/Add New Item/Web Service
• Web Service has an extension ASMX
• The CodeBehind File is stored in the App_Code
  folder.
• Web Services are defined as Web Method
• ltWebMethod()gt _

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A Web Service Example
Public Class MyWebService Inherits
System.Web.Services.WebService ltWebMethod()gt
Public Function GetCname(ByVal CID As String) As
String Dim strConn As String
"ProviderMicrosoft.Jet.OLEDB.4.0Data Source
c\salesDB.mdb" Dim objConn As New
OleDbConnection(strConn) Dim strSQL As
String "select from customer where CID '"
CID "'" Dim objComm As New
OleDbCommand(strSQL, objConn)
objConn.Open() Dim objDataReader As
OleDbDataReader objDataReader
objComm.ExecuteReader() If
objDataReader.Read() Then Return
objDataReader("Cname") Else
Return ("Not exist") End If End
Function End Class
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Web Service Description Language (WSDL)

• A WSDL file is an XML document containing a
  complete description of the web service. It
  shows a web services name, methods, and
  parameter types.
• Help page After entering web services URL, a
  help page is displayed. You can click the
  Service Description link to see the WSDL file.

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Returning an ArrayList
ltWebMethod()gt Public Function GetCnameRating(ByVa
l CID As String) As ArrayList Dim strConn
As String "ProviderMicrosoft.Jet.OLEDB.4.0Data
Source c\salesDB.mdb" Dim objConn As
New OleDbConnection(strConn) Dim strSQL
As String "select from customer where CID
'" CID "'" Dim objComm As New
OleDbCommand(strSQL, objConn)
objConn.Open() Dim objDataReader As
OleDbDataReader objDataReader
objComm.ExecuteReader() Dim temp As New
ArrayList If objDataReader.Read() Then
temp.Add(objDataReader("Cname"))
temp.Add(objDataReader("Rating"))
Else temp.Add("Not exist")
End If Return temp End Function
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Consuming Web Services from a Windows Application

• Add a web reference to the web service
• Project/Add Web Reference
• Local computer
• Imports the web service
• Declare a web service class variable.
• Dim UseWs As New DBWebService
• Note Web Service CodeBehind file location.

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Code Example (Windows Project)
Imports TestXML.MyWService Public Class Form3
Private Sub Button1_Click(ByVal sender As
System.Object, ByVal e As System.EventArgs)
Handles Button1.Click Dim MyWs As New
MyWebService Try
MessageBox.Show(MyWs.GetCname(InputBox("enter
cid "))) Catch except As
SystemException MessageBox.Show(except
.Message) End Try End Sub End Class
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Reference a Web Service on Internet

• Mortgage calculator
• http//www.webservicex.net/mortgage.asmx

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Universal Description, Discovery, and Integration
(UDDI)

• A directory service for web services.
• http//uddi.org
• UDDI is an open industry initiative enabling
  businesses to publish service listings and
  discover each other and define how the services
  or software applications interact over the
  Internet. A UDDI business registration consists
  of three components
• White Pages address, contact, and known
  identifiers
• Yellow Pages industrial categorizations based
  on standard taxonomies and
• Green Pages technical information about
  services exposed by the business.

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Loosely Coupled Software

• Refers to software routines (modules, programs)
  that can be called by an application and executed
  as needed. For example, Web services are loosely
  coupled software modules that are invoked on
  demand when required.
• An approach to designing interfaces across
  modules to reduce the interdependencies across
  modules or components in particular, reducing
  the risk that changes within one module will
  create unanticipated changes within other modules.

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Service Oriented Architecture

• SOA expresses a perspective of software
  architecture that defines the use of loosely
  coupled software services to support the
  requirements of the business processes and
  software users. In an SOA environment, resources
  on a network are made available as independent
  services that can be accessed without knowledge
  of their underlying platform implementation.
• A service-oriented architecture is not tied to a
  specific technology. It may be implemented using
  a wide range of technologies.