我已经找到了访问单个元素的方法，假设我们有一个数据流

HeartRate<Integer,Integer>

它有两个属性

private Integer Patient_id ;
private  Integer HR;

//使用自定义函数生成datasteam

DataStream<HREvent> hrEventDataStream = envrionment
                .addSource(new HRGenerator()).assignTimestampsAndWatermarks(new IngestionTimeExtractor<>());

假设您已经使用custom函数生成了datasteam，现在我们可以打印heartrateevent的各个元素的值，如下所示

hrEventDataStream.keyBy(new KeySelector<HREvent, Integer>() {
    @Override
    public Integer getKey(HREvent hrEvent) throws Exception {
        return hrEvent.getPatient_id();
    }
         })
        .window(TumblingEventTimeWindows.of(milliseconds(10)))
        .apply(new WindowFunction<HREvent, Object, Integer, TimeWindow>() {
            @Override
            public void apply(Integer integer, TimeWindow timeWindow, Iterable<HREvent> iterable, Collector<Object> collector) throws Exception {
                for(HREvent in : iterable){
                    System.out.println("Patient id  = " + in.getPatient_id() + " Heart Rate  = " + in.getHR());
                }//for
            }//apply
        });

希望有帮助！