[java][spark streamming]java.lang.IllegalArgumentException: requirement failed: No output operations registered, so nothing to execute

No output streams registered, so nothing to execute
解决原因：没有触发DStream需要的aciton
解决方法：使用以下方法之一触发：

print()
foreachRDD()
saveAsObjectFiles()
saveAsTextFiles()
saveAsHadoopFiles()