Release 10.1A: OpenEdge Development:
Programming Interfaces

Progress SAX callbacks

When the XML parser encounters an XML token, Progress invokes the callback corresponding to that token — if that callback is provided by the developer. If not, the parser continues.

Progress SAX implements callbacks as internal procedures coded by the 4GL SAX developer using signatures specified by Progress. Normally, callbacks are placed in a procedure (.p) file that the application runs persistently. But callbacks can also be placed in the driver routine. A driver routine is one that calls the SAX-PARSE() or SAX-PARSE-FIRST() method. In whichever procedure callbacks are placed, the application assigns that procedure’s handle to the SAX-reader’s HANDLER attribute. (HANDLER defaults to a handle to the driver routine). Then, the application starts the parse.

Note: Although there are many callbacks in the SAX2 interface, most applications use just a few. These are StartElement, Characters, and EndElement.

Within a callback, to get a handle to the SAX-reader object that invoked the callback, use the SELF system handle.

The following fragment uses SELF within a callback to call the SAX-reader’s STOP-PARSING() method:

SELF:STOP-PARSING().

The following fragment uses SELF within a callback to store data in the SAX-reader’s PRIVATE-DATA attribute:

SELF:PRIVATE-DATA = "xyz123".

For information on the SAX parser’s current location in the XML source, use the following attributes of SAX-reader:

LOCATOR-COLUMN-NUMBER
LOCATOR-LINE-NUMBER
LOCATOR-PUBLIC-ID
LOCATOR-SYSTEM-ID
Note: These attributes are valid only within a callback.

Table 20–2 summarizes the callbacks. For complete descriptions, see the "SAX callback reference" section.

Table 20–2: SAX callback summary 

This callback...	Lets you...
ResolveEntity	Tell the parser where to find an external entity.
StartDocument ProcessingInstruction StartPrefixMapping EndPrefixMapping StartElement Characters IgnorableWhitespace EndElement EndDocument	Process various XML tokens.
NotationDecl UnparsedEntityDecl	Process notations and unparsed entities.
Warning Error FatalError	Handle errors.