The funny thing is that in the sample questions available at Oracle's home page, one of the questions is :
SECTION: 7: 7: Building
JSP Pages Using the Expression Language (EL)
OBJECTIVE: 7.4: Given a scenario, write EL code that uses a function, write code for an EL
8) You are building an image processing web site that allows users to upload personal photographs. When presenting a photo on the display page, a colored border is generated around the image. The border color is determined from the predominate color around the edge of the photograph to provide maximum contrast. A
Java function, getBorderColor(Photograph):
String, has been created to perform this calculation and return an RGB color index. You have declared an EL function, calcColor, assigned to this Java function in the namespace p.
Which EL code snippet will return the border color for a Photograph object stored in the photo request-scoped attribute?
a) ${calcColor(photo)}
b) ${p:calcColor(photo)} (*)
c) ${getBorderColor(photo)}
d) ${p:getBorderColor(photo)}