Spark实时流计算Java案例

现在，网上基于spark的代码基本上都是Scala，很多书上也都是基于Scala，没办法，谁叫spark是Scala写出来的了，但是我现在还没系统的学习Scala，所以只能用java写spark程序了，spark支持java，而且Scala也基于JVM,不说了，直接上代码

这是官网上给出的例子，大数据学习中经典案例单词计数
在linux下一个终端 输入 $ nc -lk 9999

然后运行下面的代码

package com.tg.spark.stream;import java.util.Arrays;import org.apache.spark.*;import org.apache.spark.api.java.function.*;import org.apache.spark.streaming.*;import org.apache.spark.streaming.api.java.*;import scala.Tuple2;/** *  * @author 汤高 * */public class SparkStream {    public static void main(String[] args) {        // Create a local StreamingContext with two working thread and batch        // interval of 1 second        SparkConf conf = new SparkConf().setMaster("local[4]").setAppName("NetworkWordCount").set("spark.testing.memory",                "2147480000");        JavaStreamingContext jssc = new JavaStreamingContext(conf, Durations.seconds(1));        System.out.println(jssc);        // Create a DStream that will connect to hostname:port, like        // localhost:9999        JavaReceiverInputDStream<String> lines = jssc.socketTextStream("master", 9999);        //JavaDStream<String> lines = jssc.textFileStream("hdfs://master:9000/stream");        // Split each line into words        JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {            @Override            public Iterable<String> call(String x) {                System.out.println(Arrays.asList(x.split(" ")).get(0));                return Arrays.asList(x.split(" "));            }        });        // Count each word in each batch        JavaPairDStream<String, Integer> pairs = words.mapToPair(new PairFunction<String, String, Integer>() {            @Override            public Tuple2<String, Integer> call(String s) {                return new Tuple2<String, Integer>(s, 1);            }        });        System.out.println(pairs);        JavaPairDStream<String, Integer> wordCounts = pairs.reduceByKey(new Function2<Integer, Integer, Integer>() {            @Override            public Integer call(Integer i1, Integer i2) {                return i1 + i2;            }        });        // Print the first ten elements of each RDD generated in this DStream to        // the console        wordCounts.print();        //wordCounts.saveAsHadoopFiles("hdfs://master:9000/testFile/", "spark", new Text(), new IntWritable(), JavaPairDStream<Text,IntWritable>());        wordCounts.dstream().saveAsTextFiles("hdfs://master:9000/testFile/", "spark");        //wordCounts.saveAsHadoopFiles("hdfs://master:9000/testFile/", "spark",Text,IntWritable);        //System.out.println(wordCounts.count());        jssc.start();         //System.out.println(wordCounts.count());// Start the computation        jssc.awaitTermination();   // Wait for the computation to terminate    }}

然后再刚刚的终端输入 hello world

# TERMINAL 1:# Running Netcat$ nc -lk 9999hello world

就可以通过控制台看到

-------------------------------------------Time: 1357008430000 ms-------------------------------------------(hello,1)(world,1)...

并且hdfs上也可以看到通过计算生成的实时文件

第二个案例是，不是通过socketTextStream套接字，而是直接通过hdfs上的某个文件目录来作为输入数据源

package com.tg.spark.stream;import java.util.Arrays;import org.apache.spark.*;import org.apache.spark.api.java.function.*;import org.apache.spark.streaming.*;import org.apache.spark.streaming.api.java.*;import scala.Tuple2;/** *  * @author 汤高 * */public class SparkStream2 {    public static void main(String[] args) {        // Create a local StreamingContext with two working thread and batch        // interval of 1 second        SparkConf conf = new SparkConf().setMaster("local[4]").setAppName("NetworkWordCount").set("spark.testing.memory",                "2147480000");        JavaStreamingContext jssc = new JavaStreamingContext(conf, Durations.seconds(1));        System.out.println(jssc);        // Create a DStream that will connect to hostname:port, like        // localhost:9999        //JavaReceiverInputDStream<String> lines = jssc.socketTextStream("master", 9999);        JavaDStream<String> lines = jssc.textFileStream("hdfs://master:9000/stream");        // Split each line into words        JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {            @Override            public Iterable<String> call(String x) {                System.out.println(Arrays.asList(x.split(" ")).get(0));                return Arrays.asList(x.split(" "));            }        });        // Count each word in each batch        JavaPairDStream<String, Integer> pairs = words.mapToPair(new PairFunction<String, String, Integer>() {            @Override            public Tuple2<String, Integer> call(String s) {                return new Tuple2<String, Integer>(s, 1);            }        });        System.out.println(pairs);        JavaPairDStream<String, Integer> wordCounts = pairs.reduceByKey(new Function2<Integer, Integer, Integer>() {            @Override            public Integer call(Integer i1, Integer i2) {                return i1 + i2;            }        });        // Print the first ten elements of each RDD generated in this DStream to        // the console        wordCounts.print();        //wordCounts.saveAsHadoopFiles("hdfs://master:9000/testFile/", "spark", new Text(), new IntWritable(), JavaPairDStream<Text,IntWritable>());        wordCounts.dstream().saveAsTextFiles("hdfs://master:9000/testFile/", "spark");        //wordCounts.saveAsHadoopFiles("hdfs://master:9000/testFile/", "spark",Text,IntWritable);        //System.out.println(wordCounts.count());        jssc.start();         //System.out.println(wordCounts.count());// Start the computation        jssc.awaitTermination();   // Wait for the computation to terminate    }}

这样就存在端口一直在监控你的那个目录，只要它有文件生成，就会马上读取到它里面的内容，你可以先运行程序，然后手动添加一个文件到刚刚的目录，就可以看到输出结果了

码字不易，转载请指明出处http://blog.csdn.net/tanggao1314/article/details/51606721

参考
spark编程指南