问题描述
我正在使用 Flink，我正在使用 Kafka 连接器.我从 flink 收到的消息是一个以逗号分隔的项目列表.'a','b','c',1,0.1 ....'12:01:00.000'"其中之一包含事件时间，我想将此事件时间用于每个分区的水印(在 kafka 源中)，然后将此事件时间用于会话窗口.我的情况与平常有点不同，因为据我所知，人们通常使用kafka Timestamps"；和 SimpleStringSchema().在我的情况下，我必须编写自己的反序列化器来实现 DeserializationSchema 并返回一个元组或 Pojo.所以基本上用我自己的函数替换 SimpleStringSchema() .Flink 提供了一些开箱即用的反序列化器，但我真的不明白如何创建自定义反序列化逻辑.
检查flink网站我发现了这个:
我已经得到了一个例子(感谢大卫！)，但我仍然不明白如何实现我的.
我真的需要一个例子来说明我如何为列表做这件事.上面指出的是 JSON，所以给了我理论和概念，但我卡在那里了.
你应该像介绍POJO一样
public class Event 实现了Serializable {...私人长时间戳；}并实现类似于链接中的简单反序列化器 - 您可以解析该行，或者通过逗号手动拆分消息字符串，或者使用开箱即用的 csv 阅读器，例如 opencsv，将该行解析为您的 POJO:
public class EventDeserializationSchema 实现了 DeserializationSchema{private static final long serialVersionUID = 1L;@覆盖公共 ClickEvent deserialize(byte[] message) 抛出 IOException {String line = new String(message, StandardCharsets.UTF_8);String[] 部分 = line.split(",");事件事件 = new Event();//TODO: 此处事件的部分返回事件；}@覆盖public boolean isEndOfStream(Event nextElement) {返回假；}@覆盖公共类型信息getProducedType() {返回 TypeInformation.of(Event.class);}}I'm working with Flink and I'm using the Kafka Connector. The messages that I'm receiving from flink is a list of comma separated items. "'a','b','c',1,0.1 ....'12:01:00.000'"One of them contain the event time, I would like to use this event time for the per-partition watermarking (in the kafka source), then use this Event Time for session windowing.My case is a bit different from usual because from what i have understood people usually use "kafka Timestamps" and SimpleStringSchema(). On my case instead I have to write my own deserializer that implement DeserializationSchema and return a Tuple or Pojo. So basically substitute the SimpleStringSchema() with my own function. Flink offer out of the box some deserializers but I really don't understnd how i can create a custom deserialization logic.
Checking the flink website i have found this:
https://ci.apache.org/projects/flink/flink-docs-release-1.11/dev/connectors/kafka.html
I have been given an example (Thanks David!), but still i don't get how to implement mine.
I would really need an example of how I can do it for a list. The one indicated above is for JSON so is giving me the theory, the concept but i got stuck there.
You should introduce the POJO like
public class Event implements Serializable {
...
private Long timestamp;
}
and implement the simple deserializer similar to the one from the link - you can parse the line either manually splitting by comma the message string, or you an out-of-box csv readers, like opencsv, to parse the line into your POJO:
public class EventDeserializationSchema implements DeserializationSchema<Event> {
private static final long serialVersionUID = 1L;
@Override
public ClickEvent deserialize(byte[] message) throws IOException {
String line = new String(message, StandardCharsets.UTF_8);
String[] parts = line.split(",");
Event event = new Event();
// TODO: parts to event here
return event;
}
@Override
public boolean isEndOfStream(Event nextElement) {
return false;
}
@Override
public TypeInformation<Event> getProducedType() {
return TypeInformation.of(Event.class);
}
}
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