Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: This type (GenericTy

详细的错误信息：Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: This type (GenericType) cannot be used as key.

请看我的javabean，

// 定义一个内部类
    public static class WordCount {
        public String word;
        public long count;



        public WordCount(String word, long count) {
            this.word = word;
            this.count = count;
        }

        @Override
        public String toString() {
            return "WordCount{" +
                    "word='" + word + '\'' +
                    ", count=" + count +
                    '}';
        }
    }

请注意，一般情况下我们的代码本身没什么问题，但是今天写flink测试代码的时候出现了这个问题，我们少写了一个无参的构造函数，导致了这个错误出现，加上无参的构造函数之后就没有这个问题了。真的是一个无参构造函数触发的血案啊，血淋淋的教训。

我的详细代码如下：

package cn.yan.streaming;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.util.Collector;

/**
 * flink统计单词
 */
public class TestSocketWordCount {

    public static void main(String[] args) throws Exception {
        // 获取端口号（输入获取）
        int port;
        try {
            ParameterTool tool = ParameterTool.fromArgs(args);
            port = tool.getInt("port");
        } catch (Exception e) {
            port = 9000;
        }


        // 获取flink运行环境
        StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
        // 定义主机名（flink运行的服务器的ip）
        String hostname = "192.168.1.13";
        // 分隔符
        String delimiter = "\n";
        // 获取数据源，通过socket获取数据
        DataStreamSource text = environment.socketTextStream(hostname, port, delimiter);

        // 执行算子
        DataStream results = text.flatMap(new FlatMapFunction() {

            @Override
            public void flatMap(String value, Collector collector) {
                String[] splits = value.split("\\s");
                for (String word : splits) {
                    collector.collect(new WordCount(word, 1L));
                }
            }
        }).keyBy("word")
                // 每隔一秒连续两秒内的统计数据
                .timeWindow(Time.seconds(2), Time.seconds(1))
                .sum("count"); // 可以使用sum函数统计，也可使用reduce进行统计
//                .reduce(new ReduceFunction() {
//                    @Override
//                    public WordCount reduce(WordCount t1, WordCount t2) throws Exception {
//                        return new WordCount(t1.word, t1.count + t2.count);
//                    }
//                });


        // 把数据打印到控制台并设置并行度
        results.print().setParallelism(1);
        // 调用execute执行程序
        environment.execute("socket");
    }

    // 定义一个内部类
    public static class WordCount {
        public String word;
        public long count;



        public WordCount(String word, long count) {
            this.word = word;
            this.count = count;
        }

        @Override
        public String toString() {
            return "WordCount{" +
                    "word='" + word + '\'' +
                    ", count=" + count +
                    '}';
        }
    }
}

正确的代码为

package cn.yan.streaming;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.util.Collector;

/**
 * flink统计单词
 */
public class TestSocketWordCount {

    public static void main(String[] args) throws Exception {
        // 获取端口号（输入获取）
        int port;
        try {
            ParameterTool tool = ParameterTool.fromArgs(args);
            port = tool.getInt("port");
        } catch (Exception e) {
            port = 9000;
        }


        // 获取flink运行环境
        StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment();
        // 定义主机名（flink运行的服务器的ip）
        String hostname = "192.168.1.13";
        // 分隔符
        String delimiter = "\n";
        // 获取数据源，通过socket获取数据
        DataStreamSource text = environment.socketTextStream(hostname, port, delimiter);

        // 执行算子
        DataStream results = text.flatMap(new FlatMapFunction() {

            @Override
            public void flatMap(String value, Collector collector) {
                String[] splits = value.split("\\s");
                for (String word : splits) {
                    collector.collect(new WordCount(word, 1L));
                }
            }
        }).keyBy("word")
                // 每隔一秒连续两秒内的统计数据
                .timeWindow(Time.seconds(2), Time.seconds(1))
                .sum("count"); // 可以使用sum函数统计，也可使用reduce进行统计
//                .reduce(new ReduceFunction() {
//                    @Override
//                    public WordCount reduce(WordCount t1, WordCount t2) throws Exception {
//                        return new WordCount(t1.word, t1.count + t2.count);
//                    }
//                });


        // 把数据打印到控制台并设置并行度
        results.print().setParallelism(1);
        // 调用execute执行程序
        environment.execute("socket");
    }

    // 定义一个内部类
    public static class WordCount {
        public String word;
        public long count;


        public WordCount() {
        }

        public WordCount(String word, long count) {
            this.word = word;
            this.count = count;
        }

        @Override
        public String toString() {
            return "WordCount{" +
                    "word='" + word + '\'' +
                    ", count=" + count +
                    '}';
        }
    }
}

如图所示，启动程序之后正常执行了。

一定要加上无参的构造函数！

一定要加上无参的构造函数！

一定要加上无参的构造函数！

重要的事情说三遍！！！