Character translation error in Mapping Lookup API (RFC)

Question

Dear all,
I am new to XI and got a question concerning XI Mapping Lookup API - I send an RFC Request, which comes back as RFC Response(XML), that I fill in a String to map on.
My problem is, characters such as "Ä,ä,Ü,ß" and so on come back pretty weird and I also got a lot of quotes in my String. Could somebody please give me a hint how to move on with this..
thanx in advance
P.S. Is it usefull to handle this problem using the DOM Parser instead holding the response in a string? 
Info: called system is R/3 4.6b, XI runs on 6.4 SR 16

Answer 1

Dear all - thanks for your very fast help but I still have problem with the wrong character...
@Michal - Using this coding (the easiest way, I found from the WebLog) to convert the Payload type to String, delivers the result I have  shown at the end,  so could you give me please some approach how to handle this
               Payload resultOfCall = accessor.call(payload);
               InputStream in = resultOfCall.getContent();
               out = new ByteArrayOutputStream(1024);
               byte[] buffer = new byte[1024];
               for (int read = in.read(buffer); read > 0; read = in.read(buffer)) {
                    out.write(buffer, 0, read);
               content = out.toString();
               return content;
Result:
<?xml version="1.0" encoding="UTF-8"?><rfc:Z_GETFTXC108TXTFROMFILE2.Response xmlns:rfc="urn:sap-com:document:sap:rfc:functions"><SCENOEDITXTSTRUCT><MANDT>030</MANDT><SCENARIOID>TVPN</SCENARIOID><FILENAME>/usr/sap/text3.txt</FILENAME><FILETYPE>ASC</FILETYPE><TEXT1>Kleines Regengesicht  aaLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü2 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü3 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßß1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678906 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü3 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßß8 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÜüÖö9 ÄäBbCcDdEeFfGgÖöIxxSTRINGENDE</TEXT1><TEXT2>2 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü1234567890123456789012345678901234567890123456789012345678903 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßß1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678902 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü7 ÄäBbCcDdEeFfGgHhIiJjKkLlMmNnÖöPpQqRrSsTtÜüVvWwXxYyZzßßÖöÜü8 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÜüÖö9 ÄäBbCcDdEeFfGgÖöIxxSTRINGENDE</TEXT2><TEXT3>3 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßKleines Regengesicht  aaLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü3 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßß1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678906 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü7 ÄäBbCcDdEeFfGgHhIiJjKkLlMmNnÖöPpQqRrSsTtÜüVvWwXxYyZzßßÖöÜü8 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÜüÖö9 ÄäBbCcDdEeFfGgÖöIxxSTRINGENDE</TEXT3><TEXT4>7 ÄäBbCcDdEeFfGgHhIiJjKkLlMmNnÖöPpQqRrSsTtÜüVvWwXxYyZzßßÖöÜü7 ÄäBbCcDdEeFfGgHhIiJjKkLlMmNnÖöPpQqRrSsTtÜüVvWwXxYyZzßßÖöÜü2 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890Kleines Regengesicht  aaLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÄäÜü1234567890123456789012345678901234567890123456789012345678908 AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZzßßÜüÖö9 ÄäBbCcDdEeFfGgÖöIxxSTRINGENDE</TEXT4><TEXT5></TEXT5></SCENOEDITXTSTRUCT></rfc:Z_GETFTXC108TXTFROMFILE2.Response>
Thnaks in advance!