Map Join案例实操

DistributedCacheDriver

public class DistributedCacheDriver {

    public static void main(String[] args) throws Exception {

        // 0 根据自己电脑路径重新配置

        args = new String[]{"e:/input/inputtable2", "e:/output1"};

        // 1 获取job信息

        Configuration configuration = new Configuration();

        Job job = Job.getInstance(configuration);

        // 2 设置加载jar包路径

        job.setJarByClass(DistributedCacheDriver.class);

        // 3 关联map

        job.setMapperClass(DistributedCacheMapper.class);

        // 4 设置最终输出数据类型

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(NullWritable.class);

        // 5 设置输入输出路径

        FileInputFormat.setInputPaths(job, new Path(args[0]));

        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // 6 加载缓存数据

        job.addCacheFile(new URI("file:///e:/input/inputcache/pd.txt"));

        // 7 Map端Join（的逻辑不需要Reducer阶段，设置reducerTask数量为0

        job.setNumReduceTasks(0);

        // 8 提交

        boolean result = job.waitForCompletion(true);

        System.exit(result ? 0 : 1);

    }

}

DistributedCacheMapper

public class DistributedCacheMapper extends Mapper<LongWritable, Text, Text, NullWritable> {

    HashMap<String, String> pdMap = new HashMap<>();

    @Override

    protected void setup(Context context) throws IOException, InterruptedException {

        //缓存小表

        URI[] cacheFiles = context.getCacheFiles();

        String path = cacheFiles[0].getPath().toString();

        BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(path), "UTF-8"));

        String line;

        while (StringUtils.isNotEmpty(line = reader.readLine())) {

            // 1 切割

            String[] fileds = line.split("\t");

            pdMap.put(fileds[0], fileds[1]);

        }

        // 2 关闭资源

        IOUtils.closeStream(reader);

    }

    Text k = new Text();

    @Override

    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

        // 1 获取一行

        String line = value.toString();

        // 2 切割

        String[] fileds = line.split("\t");

        // 3 获取pid

        String pid = fileds[1];

        // 4 取出pname

        String pname = pdMap.get(pid);

        // 5 拼接

        line = line + "\t" + pname;

        k.set(line);

        // 6 写出

        context.write(k, NullWritable.get());

    }

}