38、Flink 的 WindowAssigner 之 GlobalWindows 示例

1、注意

使用 GlobalWindows 需要自定义 Trigger，否则窗口中的数据不会被计算。

2、代码示例

import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.windowing.WindowFunction;
import org.apache.flink.streaming.api.windowing.assigners.GlobalWindows;
import org.apache.flink.streaming.api.windowing.triggers.Trigger;
import org.apache.flink.streaming.api.windowing.triggers.TriggerResult;
import org.apache.flink.streaming.api.windowing.windows.GlobalWindow;
import org.apache.flink.util.Collector;

public class _05_WindowAssignerGlobal {
    public static void main(String[] args) throws Exception {
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        DataStreamSource<String> input = env.socketTextStream("localhost", 8888);

        // 此窗口模式仅在指定了自定义的 trigger 时有用，否则计算不会发生，因为全局窗口没有天然的终点去触发其中积累的数据
        input
                .keyBy(e -> e)
                // 多并行 Task
                .window(GlobalWindows.create())
                .trigger(new Trigger<String, GlobalWindow>() {
                    @Override
                    public TriggerResult onElement(String s, long l, GlobalWindow globalWindow, TriggerContext triggerContext) throws Exception {
                        return null;
                    }

                    @Override
                    public TriggerResult onProcessingTime(long l, GlobalWindow globalWindow, TriggerContext triggerContext) throws Exception {
                        return null;
                    }

                    @Override
                    public TriggerResult onEventTime(long l, GlobalWindow globalWindow, TriggerContext triggerContext) throws Exception {
                        return null;
                    }

                    @Override
                    public void clear(GlobalWindow globalWindow, TriggerContext triggerContext) throws Exception {

                    }
                })
                .apply(new WindowFunction<String, String, String, GlobalWindow>() {
                    @Override
                    public void apply(String s, GlobalWindow globalWindow, Iterable<String> iterable, Collector<String> collector) throws Exception {
                        for (String res : iterable) {
                            collector.collect(res);
                        }
                    }
                })
                .print();

        env.execute();
    }
}