code: public static File getServerOutputDir(String serverName, boolean isClient) {
          if (serverName == null) {
              throw new IllegalArgumentException("Parameter serverName can not be 'null'");
          }
          File outputDir = Utils.getOutputDir(isClient);
          if (outputDir != null) {
              return new File(outputDir, serverName);
          }
          return getServerConfigDir(serverName);
      }
docs: Returns server output directory. This directory contains server generated
  output (logs, the server's workarea, generated files, etc). It corresponds
  to the value of ${server.output.dir} variable in server.xml configuration file.
  
  @param serverName server's name
  @param isClient true if the current process is client.
  @return instance of the server output directory or 'null' if installation directory
  can't be determined.