我正在ApacheFlink中实现两个流的简单连接。我需要windowstarttime和windowendtime在窗口连接应用函数。有什么办法可以得到它们吗？我尝试了“getruntimecontext（）”，但没有成功。　　　　

streamA.join(streamB)
            .where(new KeySelector<String, String>() {
                @Override
                public String getKey(String str) throws Exception {
                    return str;
                }
            }).equalTo(new KeySelector<String, String>() {
                @Override
                public String getKey(String str) throws Exception {
                    return str;
                }
            }).window(SlidingEventTimeWindows.of(Time.seconds(windowSize), Time.seconds(windowSlideStep)))
            .apply(new JoinFunction<String, String, String>(){
    @Override
    public String join(String x, String y) throws Exception {
                    Long windowStartTime = ???
                    Long windowEndTime = ???
           }});