1、参考文档:

http://www.elasticsearch.org/guide/en/elasticsearch/hadoop/current/configuration.html

http://www.elasticsearch.org/guide/en/elasticsearch/hadoop/current/mapreduce.html#_emphasis_old_emphasis_literal_org_apache_hadoop_mapred_literal_api

2、Mapreduce相关配置

//以下ES配置主要是提供给ES的Format类进行读取使用

Configuration conf = new Configuration();

conf.set(ConfigurationOptions.ES_NODES, "127.0.0.1");

conf.set(ConfigurationOptions.ES_PORT, "9200");

conf.set(ConfigurationOptions.ES_INDEX_AUTO_CREATE, "yes");

//设置读取和写入的资源index/type

conf.set(ConfigurationOptions.ES_RESOURCE, "helloes/demo"); //read Target index/type

//假如只是想检索部分数据，可以配置ES_QUERY

//conf.set(ConfigurationOptions.ES_QUERY, "?q=me*");

//配置Elasticsearch为hadoop开发的format等

Job job = Job.getInstance(conf,ElasticsearchIndexMapper.class.getSimpleName());

job.setJarByClass(ElasticsearchIndexBuilder.class);

job.setSpeculativeExecution(false);//Disable speculative execution

job.setInputFormatClass(EsInputFormat.class);   

//假如数据输出到HDFS，指定Map的输出Value的格式。并且选择Text格式

job.setOutputFormatClass(TextOutputFormat.class);

job.setMapOutputValueClass(Text.class);

job.setMapOutputKeyClass(NullWritable.class);   

//如果选择输入到ES

job.setOutputFormatClass(EsOutputFormat.class);//输出到

job.setMapOutputValueClass(LinkedMapWritable.class);//输出的数值类 

job.setMapOutputKeyClass(Text.class);   //输出的Key值类

job.setMapperClass(ElasticsearchIndexMapper.class);

FileInputFormat.addInputPath(job, new Path("hdfs://localhost:9000/es_input"));

FileOutputFormat.setOutputPath(job, new Path("hdfs://localhost:9000/es_output"));

job.setNumReduceTasks(0);

job.waitForCompletion(true);

3、对应的Mapper类ElasticsearchIndexMapper

public class ElasticsearchIndexMapper extends Mapper {

@Override

protected void map(Object key, Object value, Context context)

        throws IOException, InterruptedException {

//假如我这边只是想导出数据到HDFS

  LinkedMapWritable doc = (LinkedMapWritable) value;   

  Text docVal = new Text();

   docVal.set(doc.toString());

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

}

}

4、小结

hadoop-ES读写最主要的就是ESInputFormat、ESOutputFormat的参数配置（Configuration）。

另外 其它数据源操作（Mysql等）也是类似，找到对应的InputFormat，OutputFormat配置上环境参数。

hadoop 读写 elasticsearch 初探