java获取程序打包成jar包/exe 同级目录下的资源文件

代码：

Properties externalResourceFile = new Properties();
String jarpath =  System.getProperty("user.dir") + "/config/externalConfig.properties";
try {
     FileInputStream in = new FileInputStream(jarpath);
     externalResourceFile.load(in);

     System.out.println(externalResourceFile.getProperty("indexPath"));

} catch (Exception e) { e.printStackTrace(); }