十二、Flink自定义 FlatMap 方法

1、概述

1）作用

flatMap是将数据先map在打平，输入一个元素，可以输出0到多个元素

2）使用

1.匿名内部类

2.lambda表达式

3.实现FlatMapFunction接口

4.继承RichFlatMapFunction

2、代码实现

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.functions.RichFlatMapFunction;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.util.Collector;

public class MyFlatmapDemo {
    public static void main(String[] args) throws Exception {
        // 创建执行环境的配置，添加webUI的端口号
        Configuration configuration = new Configuration();
        configuration.setInteger("rest.port", 8081);
        StreamExecutionEnvironment env = StreamExecutionEnvironment.createLocalEnvironmentWithWebUI(configuration);

        // 从端口接入数据
        DataStreamSource lines = env.socketTextStream("localhost", 8888);

        // 1、匿名内部类
        SingleOutputStreamOperator flatMapStream1 = lines.flatMap(new FlatMapFunction() {
            @Override
            public void flatMap(String value, Collector out) throws Exception {
                for (String word : value.split(" ")) {
                    out.collect(word);
                }
            }
        });

        // 2、lambda表达式
        SingleOutputStreamOperator flatMapStream2 = lines.flatMap((FlatMapFunction) (value, out) -> {
            for (String word : value.split(" ")) {
                out.collect(word);
            }
        }).returns(String.class);

        // 3、继承 FlatmapFunction
        SingleOutputStreamOperator flatMapStream3 = lines.flatMap(new MyFlatmapFunc());

        // 4、继承 RichFlatMapFunction
        SingleOutputStreamOperator flatMapStream4 = lines.flatMap(new MyRichFlatMapFunc());

        flatMapStream1.print();
        flatMapStream2.print();
        flatMapStream3.print();
        flatMapStream4.print();

        env.execute();
    }
}

class MyFlatmapFunc implements FlatMapFunction{
    @Override
    public void flatMap(String value, Collector out) throws Exception {
        for (String word : value.split(" ")) {
            out.collect(word);
        }
    }
}

class MyRichFlatMapFunc extends RichFlatMapFunction{
    @Override
    public void open(Configuration parameters) throws Exception {
        super.open(parameters);
        System.out.println("可以在rich方法中创建状态和定时器");
    }

    @Override
    public void close() throws Exception {
        super.close();
    }

    @Override
    public void flatMap(String value, Collector out) throws Exception {
        for (String word : value.split(" ")) {
            out.collect(word);
        }
    }
}

3、执行结果

1）输入测试数据

nc -lk 8888
hello world

控制台输出执行结果

3> hello
3> world
5> hello
5> world
8> hello
8> world
7> hello
7> world