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TUTORIAL 9
USING XML AS A DATA SOURCE
New Perspectives on XML, 2nd Edition 1
Tutorial 9
XP
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.
New Perspectives on XML, 2nd Edition 2
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USING XML AS A DATA
SOURCE
New Perspectives on XML, 2nd Edition 3
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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:
<xml id=“id” src=“URL”></xml>
• 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:
<xml id=“Company” src=“Company.xml”></xml>
• 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:
<xml id=“id”>
xml code
</xml>
• 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:
<tag datasrc=“#id” datafld=“field”>
• 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 XP
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:
<employee ID=“E304”>
<name>Alice Ashman</name>
<deptName>Accounting</deptName>
</employee>
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BINDING TO AN XML
ATTRIBUTE
• And it is interpreted by the DSO as:
<employee>
<ID>E304</ID>
<name>Alice Ashman</name>
<deptName>Accounting</deptName>
</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 <button>
as shown below:
<button onClick=“staffInfo.recordset.moveLast( )”>
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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:
<table datasrc=“#id”>
<tr>
<td><span datafld=“field1”></span></td>
<td><span datafld=“field2”></span></td>
</tr>
</table>
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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 <table> tag:
datapagesize=“number”
• 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:
<table id=“id”>
• 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 <button> tag. For
example, to move to the last page in a data table
named “StaffTable”, you enter the attribute:
onClick=“staffTable.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:
<table datasrc=“#staffInfo” datafld=“employee”>
<tr>
<td><span datafld=“name”></span></td>
<td><span datafld=“position”></span></td>
<td><span datafld=“phone”></span></td>
…
</tr>
</table>
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THE FINAL WEB PAGE
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