实现功能： 统计单词个数
代码如下：
public static void main(String[] args) throws Exception { StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment(); env.setParallelism(1); String path = "D:\\cjj\\test.txt"; DataStream<String> ds = env.readTextFile(path); SingleOutputStreamOperator<WordCountModel> maps = ds.flatMap(new FlatMapFunction<String, WordCountModel>() { @Override public void flatMap(String s, Collector<WordCountModel> out) throws Exception { String[] words = s.split("\\s"); for (String word : words) { out.collect(WordCountModel.of(word.trim(), 1l)); } } }); maps.keyBy("word").sum("num").print(); env.execute("提交任务"); }实体类：
public class WordCountModel { private String word; private Long num; private Integer age; public static WordCountModel of(String word, Long num) { WordCountModel wordCount = new WordCountModel(); wordCount.word = word; wordCount.num = num; wordCount.age = 12; return wordCount; } @Override public String toString() { return word + " " + num; } }当我们用java pojo类进行分组聚合计算时汇报如下错误信息： org.apache.flink.api.common.InvalidProgramException: This type (GenericType) cannot be used as key.
出现这种情况解决办法:
1、实体类所有变量都是public 2、keyby用到的变量不能是布尔类型的 3、添加无参构造函数（flink1.10不需要）
修改后的实体类
public class WordCountModel { public String word; public Long num; public Integer age; public static WordCountModel of(String word, Long num) { WordCountModel wordCount = new WordCountModel(); wordCount.word = word; wordCount.num = num; wordCount.age = 12; return wordCount; } @Override public String toString() { return word + " " + num; } }运行结果:
注意：实体类没有参与运算的属性也必须是public
