关于MATSIM中，如何关闭自动加载dtd的问题

有用过MATSIM做交通仿真的朋友应该都知道，在创建Scenario时，会默认加载matsim官网的netword的dtd文件，然后因为网络的问题，加载往往会报错，从而造成系统异常退出，如图所示：

根据日志提示，得知“罪魁祸首”就是MatsimXmlParser.java这个类中的第215行附近的代码，我们查找源码，找到了原因：

        // try to get the dtd from the web
        log.info("Trying to load " + systemId + ". In some cases (e.g. network interface up but no connection), this may take a bit.");
        try {
            URL url = new URL(systemId);
      URLConnection urlConn = url.openConnection();
      urlConn.setConnectTimeout(8000);
      urlConn.setReadTimeout(8000);
      urlConn.setAllowUserInteraction(false);         

      InputStream is = urlConn.getInputStream();
            /* If there was no exception until here, than the path is valid.
             * Return the opened stream as a source. If we would return null, then the SAX-Parser
             * would have to fetch the same file again, requiring two accesses to the webserver */
            return new InputSource(is);
        } catch (IOException e) {
            // There was a problem getting the (remote) file, just show the error as information for the user
            log.error(e.toString() + ". May not be fatal." ) ;
        }

虽然从代码和注释上来看，似乎加载失败并不会对程序造成致命的影响，但是从现象上来看，的确导致了程序的异常退出，并且每次运行都要加载，耗费了时间，我们可以将这段代码注释掉，并修改log日志，验证是否生效：

        // try to get the dtd from the web
        log.info("[SKIP] Trying to load " + systemId + ". In some cases (e.g. network interface up but no connection), this may take a bit.");
//        try {
//            URL url = new URL(systemId);
//      URLConnection urlConn = url.openConnection();
//      urlConn.setConnectTimeout(8000);
//      urlConn.setReadTimeout(8000);
//      urlConn.setAllowUserInteraction(false);
//
//      InputStream is = urlConn.getInputStream();
//            /* If there was no exception until here, than the path is valid.
//             * Return the opened stream as a source. If we would return null, then the SAX-Parser
//             * would have to fetch the same file again, requiring two accesses to the webserver */
//            return new InputSource(is);
//        } catch (IOException e) {
//            // There was a problem getting the (remote) file, just show the error as information for the user
//            log.error(e.toString() + ". May not be fatal." ) ;
//        }

注意，这个修改后class应该保持和源码结构中相同的包结构，在eclipse中，工程结构如图所示：

保存后再次运行matsim的应用程序，发现不会再加载dtd文件了，而且log日志也确实显示为我们修改后的日志了：