New Perspectives on XML, 2nd Edition

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TUTORIAL 9

• USING XML AS A DATA SOURCE

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USING XML AS A DATA SOURCE

• Data binding is a process by which information in
  a data source is stored as an object in computer
  memory.
• In this tutorial, the data source is an XML
  document containing information about the
  employees at Freezing Point.
• The Web pages uses placeholders which we will
  later populate with data from two XML documents.

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USING XML AS A DATA SOURCE
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DATA BINDING WITH SEVERAL WEB PAGES
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FIELDS, RECORDS, AND RECORDSETS

• Data in a data source is organized by fields,
  records, and recordsets.
• A field is an element that contains a single item
  of information such as an employees last name.
• A record is a collection of those fields.
• A recordset is a collection of records.

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FIELDS, RECORDS, AND RECORDSETS
This figure shows fields, records, and a
recordset of an XML document
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DATA ISLANDS

• The first step in data binding is to attach the
  Web page to a recordset. The attached data is
  called a data island. They can be either external
  files or code entered into the HTML file.
• The syntax to create a data island from an
  external file is
• ltxml idid srcURLgtlt/xmlgt
• Here, id is the id name assigned to the data
  island
• URL is the filename and location of the external
  XML file

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DATA ISLANDS

• For example
• ltxml idCompany srcCompany.xmlgtlt/xmlgt
• This creates a data island named Company attached
  to Company.xml.

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DATA ISLANDS

• To insert a data island directly into the HTML
  file, use this syntax
• ltxml ididgt
• xml code
• lt/xmlgt
• While this technique can be used, it is not
  recommended. After all, the philosophy of XML is
  to separate data content from data formatting.

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DATA ISLANDS

• Data islands are stored by the XML parser as a
  Data Source Object (DSO).
• The DSO takes care of the interaction between the
  Web page and the data island. Also, program code
  can be written to control the actions of the DSO
  such as specifying which records will be
  displayed in the Web page at any one time.

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CREATING A DATA ISLAND
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BINDING AN HTML ELEMENT TO A FIELD

• After the data island has been created, the
  elements in the XML document need to be bound to
  the HTML file.
• The syntax is
• lttag datasrcid datafldfieldgt
• Here, tag is the name of the HTML tag, id is the
  name of the data island, and field is the name of
  the field in the data source.

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HTML ELEMENTS THAT SUPPORT DATA BINDING
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BINDING AN HTML ELEMENT TO A FIELD
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BINDING TO AN XML ATTRIBUTE

• Attributes, like the Status attribute of the
  Employee element, are treated by the DSO as
  fields. If the attribute is part of a record
  element, it is easy to bind attribute values to a
  Web page.

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BINDING TO AN XML ATTRIBUTE

• This code has the ID attribute as part of the
  Employee element
• ltemployee IDE304gt
• ltnamegtAlice Ashmanlt/namegt
• ltdeptNamegtAccountinglt/deptNamegt
• lt/employeegt

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BINDING TO AN XML ATTRIBUTE

• And it is interpreted by the DSO as
• ltemployeegt
• ltIDgtE304lt/IDgt
• ltnamegtAlice Ashmanlt/namegt
• ltdeptNamegtAccountinglt/deptNamegt
• lt/employee
• If the attribute is part of a field element, it
  is still treated by the DSO as a field element.

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BINDING TO AN XML ATTRIBUTE

• The field element containing the attribute
  becomes a record element.
• Remember to reference all character data within
  an element using the TEXT field.
• It is a good idea not to use attributes in field
  elements if you plan to do data binding.

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BINDING TO AN XML ATTRIBUTE
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THE DATA SOURCE OBJECT

• ActiveX Data Objects (ADO) is a data-access
  technology developed by Microsoft. ADO allows you
  to work with the Data Source Object by applying a
  method or by changing one of the properties of
  the DSO.
• The syntax for applying a method is
• id.recordset.method()

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THE DATA SOURCE OBJECT

• Here, id is the name of the data island in the
  Web document and method is the name of the method
  supported by ADO.
• There are several methods that can be applied to
  DSOs.

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THE DATA SOURCE OBJECT
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THE DATA SOURCE OBJECT

• For example, if you want to display the last
  record in a DSO whose id is staffInfo, run the
  following method
• staffInfo.recordset.moveLast( )
• The simplest way to run a method is to assign the
  method to the onClick event handler of a ltbuttongt
  as shown below
• ltbutton onClickstaffInfo.recordset.moveLast(
  )gt

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THE DATA SOURCE OBJECT

• When the user clicks the button, the browser runs
  the command indicated by the onClick event
  handler, displaying the last record.

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ASSIGNING A RECORDSET METHOD
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TABLE BINDING

• Using table data binding, each record can be
  displayed in a different row of a table. The
  syntax is
• lttable datasrcidgt
• lttrgt
• lttdgtltspan datafldfield1gtlt/spangtlt/tdgt
  
• lttdgtltspan datafldfield2gtlt/spangtlt/tdgt
• lt/trgt
• lt/tablegt

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TABLE BINDING

• In the example, id is the name of the data
  island, field1, field2 are the fields from the
  recordset.

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TABLE PAGES

• As you add more records to your XML document, a
  table can become long and unwieldy. One way to
  fix this is to give the user the option of
  limiting the number of records displayed at any
  one time.
• The user can then move forward of backward that
  number of records at a time. This is called
  paging.

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TABLE PAGES

• To specify the page size, add the dataPageSize
  attribute to the lttablegt tag
• datapagesizenumber
• number is the number of records you want
  displayed in a single page.

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NAVIGATING A TABLE PAGE

• A unique identifier must be assigned to a table
  using the ID attribute before writing a command
  to navigate a table page. The syntax to do this
  is
• lttable ididgt
• Here, id is the name you assign to the table
  object.
• This is needed because the commands to navigate
  the table pages act on the table itself not the
  recordset.

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TABLE METHODS AND PROPERTIES
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TABLE METHODS AND PROPERTIES

• To run these commands, add the command to the
  onClick event handler of a ltbuttongt tag. For
  example, to move to the last page in a data table
  named StaffTable, you enter the attribute
• onClickstaffTable.lastPage( )

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HIERARCHICAL RECORDSETS
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HIERARCHICAL RECORDSETS

• To bind the Employee fields in the previous slide
  to a table, you create a table as follows
• lttable datasrcstaffInfo
  datafldemployeegt
• lttrgt
• lttdgtltspan datafldnamegtlt/spangtlt/tdgt
• lttdgtltspan datafldpositiongtlt/spangtlt/td
  gt
• lttdgtltspan datafldphonegtlt/spangtlt/tdgt
• lt/trgt
• lt/tablegt

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THE FINAL WEB PAGE