how to map portal user id and employee personal number using NWDS.

Dear All,

In my Client we are developing custom ESS application like employee appraisal.

We will intergrate these application into portal using webdynpro java iview.

Now my question is..

employee logs into portal with his user id and password( user accessing employee appraisal like webdynpro java application),then in his custom ESS applications how can we fetch the corresponding employee data.how can we get the user...

in this employee appraisal application having

two input fields like

1.start date(user enter date manually).

2.perner no(Automatically get the perner number who is logged into portal).that means portal user id is equal to r/3 pa30 perner number.

in which RFC i need to call into webdynpro java.how can i map into portal user id into r/3 perner number.

I hope you guys understand my question.

Tanks@Regards

Pradeep