6 IF-THEN and OR conditions for one target field mapping

Question

Hi Mapping experts,
I have a validation condition involving 2 source fields and 1 target field only, however the number of conditions is 6 (OR)
Source Fields:
TYPE
PONUM
Target Field:
BELNR
If TYPE = 1st value   then   BELNR = PONUM substring (0, 8)  0=start position, 8=character count
OR
If TYPE = 2nd value   then   BELNR = PONUM substring (2, 8)
OR
if TYPE = 3rd value  then  BELNR = PONUM substring (4, 8) ..........  up to the 6th Validation Condition.
When I do this using graphical mapping only (multiple IF-THEN and OR's) the validation is successful only on the 1st IF-THEN statement, then it passes the substringed value to the 1st OR function.....    When I "Display Queue" the 1st OR function the substringed value is taken as null (or:in1 <null>)  Is this because OR function is expecting Input as "True or False" value only and not a string value?
For my requirement above, can I achieve this using graphical mapping only?    or do I have to use UDF for this?
If it's better to use UDF for this, would anyone give me a jumpstart on the code?  (I have no experience yet in UDFs)
Thanks, and hoping that somebody will respond accurately and completely.

Answer 1

Create UDF with two inputs as TYPE & PONUM and use bleow code there..
String out = "";
if( TYPE.equals("1"))
out = PONUM.substring(0,8);
return out;
else if( TYPE.equals("2"))
out = PONUM.substring (2,8);
return out;
else if( TYPE.equals("3"))
out = PONUM.substring (4,8);
return out;
else if( TYPE.equals("4"))
out = PONUM.substring (4,8);
return out;
else if( TYPE.equals("5"))
out = PONUM.substring (4,8);
return out;
else if( TYPE.equals("6"))
out = PONUM.substring (4,8);
return out;
return "";
Note: change the substring range as per your need in above code.
Now do your mapping as shown below
TYPE ------>|
            | -----> UDF ---> BELNR
PONUM----->|