java spark开发中，UnknownHostException

在java spark开发中，读取hdfs上文件时，出现UnknownHostException，此问题解决方法：

方法一：
拷贝core-site.xml, hdfs-site.xml到工程目录的resources下

方法二：

// prefixConf: 一定要带上schema: file://, 如： file:///home/work/hadoop
Configuration configuration = new Configuration();
configuration.addDefaultResource(prefixConf + "/core-site.xml");
configuration.addDefaultResource(prefixConf + "/hdfs-site.xml");

方法三：

  String prefixConf = "file://" + hdfsConf;
  String master = "local";
  SparkConf sparkConf = new SparkConf();
  sparkConf.setAppName("spark-demo");
  sparkConf.setMaster(master);
  sc = new JavaSparkContext(sparkConf);
  sc.hadoopConfiguration().addResource(prefixConf + "/core-site.xml"); // 必须要告知协议，如file://,否则不生效
  sc.hadoopConfiguration().addResource(prefixConf + "/hdfs-site.xml");    

方法四：

  String prefixConf = "file://" + hdfsConf;
  String master = "local";
  SparkConf sparkConf = new SparkConf();
  sparkConf.setAppName("spark-demo");
  sparkConf.setMaster(master);
  sc = new JavaSparkContext(sparkConf);
  sc.hadoopConfiguration().addResource(new File(hdfsConf + "/core-site.xml").toURI().toURL()); 
  sc.hadoopConfiguration().addResource(new File(hdfsConf + "/hdfs-site.xml").toURI().toURL());