OpenEdge Development: Working with XML - Product ...

The ABL DOM interface
If you are an ABL programmer not yet experienced with built-in ABL objects, then you will
find this an easy skill to acquire. If you do not understand something in this chapter, you can
refer to the OpenEdge Development: ABL Reference for complete information about the object,
handle, attribute, or method. Note that this ABL skill level does not require you to know or
understand the support for true object-oriented programming also provided by the ABL. Think
of ABL built-in or system objects as useful, consistent, easy-to-use encapsulations of system
resources or technologies that increase the richness of the ABL programming environment.
Representing an XML document in ABL DOM
DOM builds a hierarchical tree structure that persists in memory and represents your entire
XML document. With the ABL interface, you can call the parser to build such a tree for you in
memory from an XML document. The DOM tree is then available for you to easily manipulate
using standard tree-traversal logic. For example, an XML document may represent a list of
address changes generated from a self-service Web site. Your application might need to traverse
the tree and do some logical validation before using the XML data in the tree to update customer
address records in your database.
You could also use the API to programmatically build a DOM tree in memory and then write
that tree out as an XML document. For example, you may need to generate a list of customer
address changes for a business partner.
Note: ABL has defined a set of extensions to ABL to allow the use of XML through the DOM
interface. These extensions provide ABL applications with the basic input, output, and
low-level data manipulation capabilities required to use data contained in XML
documents. They are not intended to provide access to the entire DOM interface, nor
are they intended to include all the high-level constructs.
In an ABL application, an X-document object can represent an XML document. Like all ABL
objects, the programming flow for using an X-document object follows this pattern:
• Define a variable of type HANDLE
• Use the appropriate CREATE statement to create the object in memory and assign the pointer
to that object to your HANDLE variable—the HANDLE variable is your interface to the object
• Use attributes and methods on the handle to initialize or configure the object
• Use attributes and methods on the handle to complete your programming tasks
• Use the DELETE OBJECT statement to destroy the object and remove it from memory
For example:
DEFINE VARIABLE hDocument AS HANDLE NO-UNDO.
CREATE X-DOCUMENT hDocument.
. . .
DELETE OBJECT hDocument.
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