Spark自定义累加器

package com.sparkproject.abc;

import org.apache.spark.AccumulatorParam;

 public class UDFAccumulatorClass implements AccumulatorParam<String> {

    private static final long serialVersionUID = 1L;

    @Override
    public String addAccumulator(String v1, String v2) {
        return add(v1, v2);
    }

    @Override
    public String addInPlace(String r1, String r2) {
        return add(r1, r2);
    }

    @Override
    public String zero(String initialValue) {
        return "Accumulator:0";
    }

    public String add(String v1, String v2) {
        if(v1 == null || "".equals(v1)) {
            return v2;
        }
        String[] val = v1.split(":");
        return val[0] + ":" + val[1] + v2;
    }

}

package com.sparkproject.abc;

import org.apache.spark.Accumulator;
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.PairFunction;
import org.apache.spark.api.java.function.VoidFunction;
import scala.Tuple2;

import java.util.Arrays;
 public class UDFAccumulator {

    public static void main(String[] args) {

        SparkConf conf = new SparkConf()
                .setMaster("local")
                .setAppName("Accumu");
        JavaSparkContext sc = new JavaSparkContext(conf);
        final Accumulator<String> udf = sc.accumulator("",new UDFAccumulatorClass());
        JavaRDD<Integer> javaRDD = sc.parallelize(Arrays.asList(1,2,3,4,5));
        JavaPairRDD<Integer, Integer> javaPairRDD = javaRDD.mapToPair(new PairFunction<Integer, Integer, Integer>() {
            @Override
            public Tuple2<Integer, Integer> call(Integer integer) throws Exception {
                udf.add(integer + "");
                return new Tuple2<Integer, Integer>(integer, integer);
            }
        });
        javaPairRDD.foreach(new VoidFunction<Tuple2<Integer, Integer>>() {
            @Override
            public void call(Tuple2<Integer, Integer> integerIntegerTuple2) throws Exception {
                System.out.println(integerIntegerTuple2);
            }
        });
        System.out.println(udf.value());

    }
}