下面是我使用系统类加载器的过程，我将它添加到hadoop驱动程序类中

public static void logClasspathToStdOut() {
    try {
      ClassLoader cl = ClassLoader.getSystemClassLoader();

      URL[] urls = ((URLClassLoader)cl).getURLs();

      int i = 1;
      System.out.println("SystemClassLoader classpath includes:");
      for (URL url : urls) {
        System.out.println(i + " : " + url.getFile());
        i++;
      }
    } catch(Exception e) {
      System.err.println("Exception logging classpath " + e.getMessage());
    }
  }

（阅读这里的类加载器类型之间的区别线程的上下文类加载器和普通类加载器之间的区别）
我在emr的stdout上得到了以下输出

SystemClassLoader classpath includes:
1 : /home/hadoop/.versions/2.4.0/etc/hadoop/
2 : /home/hadoop/.versions/2.4.0/share/hadoop/common/lib/httpclient-4.2.5.jar
3 : /usr/share/aws/emr/kinesis/lib/EmrKinesisHadoop-1.0.1.jar
.
.
354 : /usr/share/aws/emr/lib/gson-2.2.2.jar
355 : /usr/share/aws/emr/lib/commons-httpclient-3.0.jar