Activities, flows, and a few other rule types may have parameters that can be accepted as inputs (by value), used to convey results (by value), or serve as both inputs and outputs.
A parameter page contains parameter names and values. This page has no name or associated class. The stack of parameter pages for the current process is not part of the clipboard, and is not visible through the Clipboard tool. However, you can display the contents of the parameter page with the Tracer tool.
Each call or branch (or form SUBMIT by a user) that starts a new execution of an activity uses a parameter page to convey these input parameters and to access the results of the activity's execution.
Flow parameters and activity parameters are scalar and can hold only a
single string. Within an activity or a flow rule, the keyword
Param
and a dot identifies a parameter (or its string value
depending on context), as in:
Param.Width
Each activity of can define the names of the parameters it expects, the data type of each, and other constraints on the Parameters tab of the Activity form. The name of a parameter must be a Java identifier.
Local variables are also defined on the Parameter tab of the Activity form, but are passed within a StringBuffer rather than through a page, for efficiency reasons.
Section rules and control rules accept both scalar and complex
parameters. Complex parameters mimic the structure of the Value
List
, Value Group
, Page List
, and
Page Group
property types, though the parameters are not
defined by property rules. PROJ-1128 5.4
Use the <pega:param .. > JSP tag (within the <pega:reference..> JSP tag) to set the value of a complex parameter.