Question

I m using new Hadoop API and looking for a way to pass some parameters (few strings) to mappers.
How can I do that?

JobConf job = (JobConf)getConf();
job.set("NumberOfDocuments", args[0]);

这里,“NumberOfDocuments”是指参数的名称,其价值从“args[0],即一条指挥线。一俟你提出这一论点,你就可收回其价值,即:

private static Long N;
public void configure(JobConf job) {
     N = Long.parseLong(job.get("NumberOfDocuments"));
}

值得注意的是,微小部分是,你不能确定这样的参数:

Configuration con = new Configuration();
con.set("NumberOfDocuments", args[0]);

Answer 1

Configuration conf = new Configuration();
conf.set("test", "123");

Job job = new Job(conf);

在地图仪/测量仪中,参数为参数。

Configuration conf = context.getConfiguration();
String param = conf.get("test");