开发者学堂课程【Hadoop 企业优化及扩展案例：多 Job 串联案例完成】学习笔记，与课程紧密联系，让用户快速学习知识。
课程地址：https://developer.aliyun.com/learning/course/96/detail/1574
多 Job 串联案例完成
目录：
一．写 TwolndexMapper.
二．将 mapper 写入 reducer
三．驱动
1. 写 TwolndexMapper.
protected void map( LongWritable key, Text value, Mapper .Context context)throws I0Exception, InterruptedException {atguigu--a.txt
atguigu--b.txt
atguigu--c.txt
// 1获取一行String line = value.toString();
// 2切割String[] fields = line.split("--");
// 3封装Text k = new Text();Text v = new Text();
// 3写出context.write(key, value);
2. 将 mapper 写入 reducer
public class TwoIndexReducer extends Reducer
@0verrideprotected void reduce(Text key,Iterable values, Context context)
throws I0Exception, InterruptedException f
atguigu --a.txt 3
--b.txt 2
--c.txt 2atguigu c.txt-->2 b.txt-->2 a.txt-->3
// 1拼接字符串StringBuffer sb = new StringBuffer();for (Text value : values) { sb. append(value.toString().replace("\t","-->") +"\t");
v.set(sb.toString());
// 2写出context.write(key, v);
}
3. 驱动
