Flink支持用户自定义 Functions，方法有2个

Ref

https://ci.apache.org/projects/flink/flink-docs-release-1.12/zh/dev/user_defined_functions.html

1. 实现 MapFunction接口

class MyMapFunction implements MapFunction<String, Integer> {
  public Integer map(String value) { return Integer.parseInt(value); }
};
data.map(new MyMapFunction());

2. 继承 RichMapFunction

class MyMapFunction extends RichMapFunction<String, Integer> {
  public Integer map(String value) { return Integer.parseInt(value); }
};

 

累加器和计数器

这个应该和Hadoop和Spark的counter类似，参考

https://ci.apache.org/projects/flink/flink-docs-release-1.12/zh/dev/user_defined_functions.html#%E7%B4%AF%E5%8A%A0%E5%99%A8%E5%92%8C%E8%AE%A1%E6%95%B0%E5%99%A8