Exception in thread "main" org.apache.hadoop.mapred.InvalidInputException: Input path does not exist: file:/home/hadoop/workspace/Web/user_conversion.json
似乎你在MapReduce程序中提供了错误的路径。首先，检查该文件是否存在于Hadoop Hdfs中。否则，您可以使用下面的命令将文件放到Hadoop
hadoop fs -put <datafile> /user/hduser/input