作者：Syn良子 出处：http://www.cnblogs.com/cssdongl 转载请注明出处

大家都知道用mapreduce或者spark写入已知的hbase中的表时，直接在mapreduce或者spark的driver class中声明如下代码

job.getConfiguration().set(TableOutputFormat.OUTPUT_TABLE, tablename);

随后mapreduce在mapper或者reducer中直接context写入即可,而spark则是构造好包含Put的PairRDDFunctions后saveAsHadoopDataset即可.

而经常会碰到一些要求是根据输入数据，处理后需要写入hbase多个表或者表名是未知的，需要按照数据中某个字段来构造表名写入hbase.

由于表名未知，所以不能设置TableOutputFormat.OUTPUT_TABLE,那么这种要求也容易实现，分别总结mapreduce和spark的实现方法(其实到最后会发现殊途同归)

一.MapReduce写入Hbase多表

在MR的main方法中加入如下代码即可

job.setOutputFormatClass(MultiTableOutputFormat.class);

随后就可以在mapper或者reducer的context中根据相关字段构造表名和put写入多个hbase表.

二.Spark写入Hbase多表

这里直接用我测试过的spark streaming程序写入多个hbase表，上代码

object SparkStreamingWriteToHbase {
  def main(args: Array[String]): Unit = {
    var masterUrl = "yarn-client"
    if (args.length > 0) {
      masterUrl = args(0)
    }
    val conf = new SparkConf().setAppName("Write to several tables of Hbase").setMaster(masterUrl)

    val ssc = new StreamingContext(conf, Seconds(5))

    val topics = Set("app_events")

    val brokers = PropertiesUtil.getValue("BROKER_ADDRESS")

    val kafkaParams = Map[String, String](
      "metadata.broker.list" -> brokers, "serializer.class" -> "kafka.serializer.StringEncoder")

    val hbaseTableSuffix = "_clickcounts"

    val hConf = HBaseConfiguration.create()
    val zookeeper = PropertiesUtil.getValue("ZOOKEEPER_ADDRESS")
    hConf.set(HConstants.ZOOKEEPER_QUORUM, zookeeper)

    val jobConf = new JobConf(hConf, this.getClass)

    val kafkaDStreams = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder](ssc, kafkaParams, topics)

    val appUserClicks = kafkaDStreams.flatMap(rdd => {
      val data = JSONObject.fromObject(rdd._2)
      Some(data)
    }).map{jsonLine =>
        val key = jsonLine.getString("appId") + "_" + jsonLine.getString("uid")
        val value = jsonLine.getString("click_count")
        (key, value)
    }

    val result = appUserClicks.map { item =>
      val rowKey = item._1
      val value = item._2
      convertToHbasePut(rowKey, value, hbaseTableSuffix)
    }

    result.foreachRDD { rdd =>
 rdd.saveAsNewAPIHadoopFile("", classOf[ImmutableBytesWritable], classOf[Put], classOf[MultiTableOutputFormat], jobConf) }

    ssc.start()
    ssc.awaitTermination()
  }

  def convertToHbasePut(key: String, value: String, tableNameSuffix: String): (ImmutableBytesWritable, Put) = {
    val rowKey = key
    val tableName = rowKey.split("_")(0) + tableNameSuffix
    val put = new Put(Bytes.toBytes(rowKey))
    put.addColumn(Bytes.toBytes("info"), Bytes.toBytes("count"), Bytes.toBytes(value))
    (new ImmutableBytesWritable(Bytes.toBytes(tableName)), put)
  }

}

简单描述下，这里spark streaming中处理的是从kafka中读取的json数据，其中的appId字段用来构造tablename区分写入不同的hbase table.最后以saveAsNewAPIHadoopFile把rdd写入hbase表

进入saveAsNewAPIHadoopFile会发现其实和mapreduce的配置没什么区别，如下

def saveAsNewAPIHadoopFile(
      path: String,
      keyClass: Class[_],
      valueClass: Class[_],
      outputFormatClass: Class[_ <: NewOutputFormat[_, _]],
      conf: Configuration = self.context.hadoopConfiguration)
  {
    // Rename this as hadoopConf internally to avoid shadowing (see SPARK-2038).
    val hadoopConf = conf
    val job = new NewAPIHadoopJob(hadoopConf)
    job.setOutputKeyClass(keyClass)
    job.setOutputValueClass(valueClass)
    job.setOutputFormatClass(outputFormatClass)
    job.getConfiguration.set("mapred.output.dir", path)
    saveAsNewAPIHadoopDataset(job.getConfiguration)
  }

这个方法的参数分别是ouput path,这里写入hbase，传入为空即可，其他参数outputKeyClass,outputValueClass,outputFormatClass,jobconf

这里的outputFormatClass确保一定是MultiTableOutputFormat来保证写入多表,对了，这里说明一点，确保你要写入的hbase表首先被create了。