code: private void doHandleAs(Subject subject, final HttpExchange pHttpExchange) {
          try {
              Subject.doAs(subject, new PrivilegedExceptionAction<Void>() {
              public Void run() throws IOException {
                  doHandle(pHttpExchange);
                  return null;
              }
              });
          } catch (PrivilegedActionException e) {
              throw new SecurityException("Security exception: " + e.getCause(),e.getCause());
          }
      }
docs: run as priviledged action