Spark 例子

1、Java下Spark开发环境搭建（from http://www.cnblogs.com/eczhou/p/5216918.html）

1.1、jdk安装

安装oracle下的jdk，我安装的是jdk 1.7，安装完新建系统环境变量JAVA_HOME，变量值为“C:\Program Files\Java\jdk1.7.0_79”，视自己安装路劲而定。

同时在系统变量Path下添加C:\Program Files\Java\jdk1.7.0_79\bin和C:\Program Files\Java\jre7\bin。

1.2 spark环境变量配置

去http://spark.apache.org/downloads.html网站下载相应hadoop对应的版本，我下载的是spark-1.6.0-bin-hadoop2.6.tgz，spark版本是1.6，对应的hadoop版本是2.6

解压下载的文件，假设解压 目录为：D:\spark-1.6.0-bin-hadoop2.6。将D:\spark-1.6.0-bin-hadoop2.6\bin添加到系统Path变量，同时新建SPARK_HOME变量，变量值为：D:\spark-1.6.0-bin-hadoop2.6

1.3 hadoop工具包安装

spark是基于hadoop之上的，运行过程中会调用相关hadoop库，如果没配置相关hadoop运行环境，会提示相关出错信息，虽然也不影响运行，但是这里还是把hadoop相关库也配置好吧。

1.3.1 去下载hadoop 2.6编译好的包https://www.barik.net/archive/2015/01/19/172716/，我下载的是hadoop-2.6.0.tar.gz，

1.3.2 解压下载的文件夹，将相关库添加到系统Path变量中：D:\hadoop-2.6.0\bin；同时新建HADOOP_HOME变量，变量值为：D:\hadoop-2.6.0

1.4 eclipse环境

直接新建java工程，将D:\spark-1.6.0-bin-hadoop2.6\lib下的spark-assembly-1.6.0-hadoop2.6.0.jar添加到工程中就可以了。

2、Java写Spark WordCount程序‘

package cn.spark.study;

import java.util.Arrays;

import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;
import org.apache.spark.api.java.function.VoidFunction;

import scala.Tuple2;

public class WordCount {
    public static void main(String[] args) {

        //创建 SparkConf对象，对程序进行必要的配置
        SparkConf conf = new SparkConf()
        .setAppName("WordCount").setMaster("local");

        //通过conf创建上下文对象
        JavaSparkContext sc = new JavaSparkContext(conf);

        //创建初始RDD
        JavaRDD<String> lines = sc.textFile("D://spark.txt");

        //----用各种Transformation算子对RDD进行操作-----------------------------------------
        JavaRDD<String> words = lines.flatMap(new FlatMapFunction<String, String>() {

            private static final long serialVersionUID = 1L;

            @Override
            public Iterable<String> call(String line) throws Exception {
                // TODO Auto-generated method stub
                return Arrays.asList(line.split(" "));
            }
        });

        JavaPairRDD<String,Integer> pairs = words.mapToPair(new PairFunction<String, String, Integer>() {

            private static final long serialVersionUID = 1L;

            @Override
            public Tuple2<String, Integer> call(String word) throws Exception {
                // TODO Auto-generated method stub
                return new Tuple2<String,Integer>(word,1);
            }
        });

        JavaPairRDD<String,Integer> wordCounts = pairs.reduceByKey(new Function2<Integer, Integer, Integer>() {

            private static final long serialVersionUID = 1L;

            @Override
            public Integer call(Integer v1, Integer v2) throws Exception {
                // TODO Auto-generated method stub
                return v1 + v2;
            }
        });

        //----用一个 action 算子触发job-----------------------------------------
        wordCounts.foreach(new VoidFunction<Tuple2<String,Integer>>() {

            @Override
            public void call(Tuple2<String, Integer> wordCount) throws Exception {
                // TODO Auto-generated method stub
                System.out.println(wordCount._1 + " appeared " + wordCount._2 + " times");
            }
        });
    }