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我使用下面的代码写一个RDD作为一个序列文件无法写入与火花RDD API序列文件
@Test
def testSparkWordCount(): Unit = {
val words = Array("Hello", "Hello", "World", "Hello", "Welcome", "World")
val conf = new SparkConf().setMaster("local").setAppName("testSparkWordCount")
val sc = new SparkContext(conf)
val dir = "file:///" + System.currentTimeMillis()
sc.parallelize(words).map(x => (x, 1)).saveAsHadoopFile(
dir,
classOf[Text],
classOf[IntWritable],
classOf[org.apache.hadoop.mapred.SequenceFileOutputFormat[Text, IntWritable]]
)
sc.stop()
}
当我运行它,它抱怨说
Caused by: java.io.IOException: wrong key class: java.lang.String is not class org.apache.hadoop.io.Text
at org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:1373)
at org.apache.hadoop.mapred.SequenceFileOutputFormat$1.write(SequenceFileOutputFormat.java:76)
at org.apache.spark.internal.io.SparkHadoopWriter.write(SparkHadoopWriter.scala:94)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsHadoopDataset$1$$anonfun$12$$anonfun$apply$4.apply$mcV$sp(PairRDDFunctions.scala:1139)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsHadoopDataset$1$$anonfun$12$$anonfun$apply$4.apply(PairRDDFunctions.scala:1137)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsHadoopDataset$1$$anonfun$12$$anonfun$apply$4.apply(PairRDDFunctions.scala:1137)
at org.apache.spark.util.Utils$.tryWithSafeFinallyAndFailureCallbacks(Utils.scala:1360)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsHadoopDataset$1$$anonfun$12.apply(PairRDDFunctions.scala:1145)
at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsHadoopDataset$1$$anonfun$12.apply(PairRDDFunctions.scala:1125)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
应该我必须使用sc.parallelize(words).map(x => (new Text(x), new IntWritable(1))
而不是sc.parallelize(words).map(x => (x, 1))
?我不认为我必须明确地包装它,因为SparkContext已经提供了将前缀类型包装到相应的Writable中的含义。
所以,我应该怎么做才能让这段代码工作
明白了,谢谢@pashaz为有用的答案 – Tom
也为包括隐式转换,可以用“saveAsSequenceFile”的方法: .MAP (x =>(x,1))。saveAsSequenceFile(dir) – pasha701