java.io.IOException: No FileSystem for scheme: hdfs

在用Scala写spark时候，用了sc操作了hdfs，出现了如下错误：

java.io.IOException: No FileSystem for scheme: hdfs
    at org.apache.hadoop.fs.FileSystem.getFileSystemClass(FileSystem.java:2660)
    at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2667)
    at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:94)
    at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2703)
    at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2685)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:373)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:172)
    at org.apache.spark.deploy.yarn.Client$$anonfun$5.apply(Client.scala:123)
	at org.apache.spark.deploy.yarn.Client$$anonfun$5.apply(Client.scala:123)
    at scala.Option.getOrElse(Option.scala:121)
    at org.apache.spark.deploy.yarn.Client.(Client.scala:123)
    at org.apache.spark.deploy.yarn.Client.(Client.scala:69)
    at org.apache.spark.scheduler.cluster.YarnClientSchedulerBackend.start(YarnClientSchedulerBackend.scala:55)
    at org.apache.spark.scheduler.TaskSchedulerImpl.start(TaskSchedulerImpl.scala:173)
    at org.apache.spark.SparkContext.(SparkContext.scala:509)

解决方案1：

val hadoopConf = spark(这个是SparkSession变量名).sparkContext.hadoopConfiguration
hadoopConf.set("fs.hdfs.impl", classOf[org.apache.hadoop.hdfs.DistributedFileSystem].getName)
hadoopConf.set("fs.file.impl", classOf[org.apache.hadoop.fs.LocalFileSystem].getName)

解决方案2：
在core-site.xml中加入如下配置，并且重启，以后每次都会生效。

<property>
   <name>fs.file.implname>
   <value>org.apache.hadoop.fs.LocalFileSystemvalue>
property>

<property>
  <name>fs.hdfs.implname>
  <value>org.apache.hadoop.hdfs.DistributedFileSystemvalue>
property>