code: public static String exception2StringShort(Exception e) {
          StringBuffer st = new StringBuffer();
          Throwable e2 = e;
  
          while (e2 != null) {
              String exClass = e2.getClass().getName();
              String msg = e2.getMessage();
  
              if (msg != null) {
                  st.setLength(0);
                  st.append(exClass);
                  st.append(": ");
                  st.append(msg);
              }
              e2 = e2.getCause();
          }
  
          return st.toString().trim();
      }
docs: Extrahieren der root-Exception aus einer Exception-Chain.
  
  @param e Exception
  @return String mit Infos zur root-Exception