About this task
You can transform pattern parameters by using XPath expressions;
for example, to calculate a pattern parameter value from the values
entered for other pattern parameters.
IBM® Integration Bus supports XPath 1.0. For XPath
reference information, including information about XPath functions,
see
W3C XPath 1.0 Specification.
- The pp:getValue() function is included, in addition
to the functions in the XPath 1.0 Specification. The pp:getValue() function
takes the parameter ID of a pattern parameter and returns the value
of that pattern parameter. To see the parameter ID for a pattern parameter:
- In the Pattern
Configuration tab of the
Pattern Authoring editor, double-click a parameter, or select a parameter
and click Edit. The Edit Parameter window
opens.
- Click the Transform tab. The parameter
IDs for pattern parameters are shown in the Parameter ID column
of the Pattern Parameters table.
- When a pattern instance is generated by a pattern user, transformation
expressions are processed before any Java™ and
PHP code that has been added to modify pattern instances. Transformation
of pattern parameters is processed in the following sequence:
- Every parameter that has an XPath transformation expression is
evaluated.
- The value of each parameter that has an XPath transformation expression
is updated with the result of its evaluation, overwriting the value
entered by the pattern user.
- The parameters are evaluated in top to bottom order, as they are
listed in the Pattern
Configuration tab of the
Pattern Authoring editor.