mapreduce提交作业出现报错信息

Question

我最近采用这种方法提交作业，把mr作业的业务逻辑打包上传至hdfs中，在eclipse中提交任务（不安装hadoop插件），报错Error: java.io.IOException: Unable to initialize any output collector，如果把mr作业的业务逻辑打包上传至hdfs节点上，就可以顺利完成。
这是为什么？
Configuration conf = new Configuration();
conf.set("mapreduce.job.name","count22");
conf.set("mapreduce.job.jar", "hdfs://172.16.200.210:8020/user/root/testjar/hadoopTest.jar");
conf.set("mapreduce.job.output.key.class", "org.apache.hadoop.io.Text");
conf.set("mapreduce.job.output.value.class", "org.apache.hadoop.io.IntWritable");
conf.set("mapred.mapper.class", "hadoop.test$Map");
conf.set("mapred.reducer.class", "hadoop.test$Reduce");
conf.set("mapred.combiner.class", "hadoop.test$Reduce");
conf.set("mapred.input.format.class", "org.apache.hadoop.mapred.TextInputFormat");
conf.set("mapred.output.format.class", "org.apache.hadoop.mapred.TextOutputFormat");
conf.set("mapreduce.input.fileinputformat.inputdir",
"hdfs://172.16.200.210:8020/user/root/input/count.txt");
conf.set("mapreduce.output.fileoutputformat.outputdir",
"hdfs://172.16.200.210:8020/user/root/sc");
JobConf jobconf=new JobConf(conf);
JobClient.runJob(jobconf);