我正在做一个Flink项目。该项目的主要思想是读取JSON的数据流(网络日志),关联它们,并生成一个新的JSON,它是不同JSON信息的组合。
此时,我能够读取JSON,生成KeyedStream(基于生成日志的机器),然后生成5秒的窗口流。
我想要执行的下一步是对窗口使用apply函数并组合每个JSON的信息。我对如何做到有点困惑。
我目前的代码如下:
DataStream<Tuple2<String,JSONObject>> MetaAlert = events
.flatMap(new JSONParser())
.keyBy(0)
.timeWindow(Time.seconds(5))
.apply(new generateMetaAlert());
public static class generateMetaAlert implements WindowFunction<Tuple2<String,JSONObject>, Tuple2<String,JSONObject>, String, Window> {
@Override
public void apply(String arg0, Window arg1, Iterable<Tuple2<String, JSONObject>> arg2,
Collector<Tuple2<String, JSONObject>> arg3) throws Exception {
}
.apply(new generateMetaAlert())部分正在抱怨下一个错误:
方法apply(WindowFunction,R,Tuple,TimeWindow>)在WindowedStream类型中,Tuple,TimeWindow>不适用于参数(MetaAlertGenerator.generateMetaAlert)
任何其他代码结构提案都与我编写的提案截然不同?
预先感谢您的帮助
当您应用keyBy
函数(不使用匿名类)时,自定义WindowFunction
(第3个字段)中的键的类型应为Tuple
,因为编译器无法确定键的类型。此代码编译时没有错误(考虑到我试图用虚拟代码填充空白):
public class Test {
public Test() {
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
DataStream<String> events = env.readTextFile("datastream.log");
DataStream<Tuple2<String, JSONObject>> MetaAlert
= events
.flatMap(new JSONParser())
.keyBy(0)
.timeWindow(Time.seconds(5))
.apply(new GenerateMetaAlert());
}
public class JSONObject {
}
public class JSONParser implements FlatMapFunction<String, Tuple2<String, JSONObject>> {
@Override
public void flatMap(String s, Collector<Tuple2<String, JSONObject>> collector) throws Exception {
}
}
public class GenerateMetaAlert implements WindowFunction<Tuple2<String, JSONObject>, Tuple2<String, JSONObject>, Tuple, TimeWindow> {
@Override
public void apply(Tuple key, TimeWindow timeWindow, Iterable<Tuple2<String, JSONObject>> iterable, Collector<Tuple2<String, JSONObject>> collector) throws Exception {
}
}
}
但最直接的方法是使用匿名类,以便您可以保持String
类型:
DataStream<Tuple2<String, JSONObject>> MetaAlert
= events
.flatMap(new JSONParser())
.keyBy(0)
.timeWindow(Time.seconds(5))
.apply(new WindowFunction<Tuple2<String, JSONObject>, Tuple2<String, JSONObject>, Tuple, TimeWindow>() {
@Override
public void apply(Tuple tuple, TimeWindow timeWindow, Iterable<Tuple2<String, JSONObject>> iterable, Collector<Tuple2<String, JSONObject>> collector) throws Exception {
// Your code here
}
});
最后,如果你想保留这个类,但你也想保持你的键的类型,你可以实现一个KeySelector
:
public class Test {
public Test() {
DataStream<Tuple2<String, JSONObject>> MetaAlert
= events
.flatMap(new JSONParser())
.keyBy(new KeySelector<Tuple2<String,JSONObject>, String>() {
@Override
public String getKey(Tuple2<String, JSONObject> json) throws Exception {
return json.f0;
}
})
.timeWindow(Time.seconds(5))
.apply(new GenerateMetaAlert());
}
public class GenerateMetaAlert implements WindowFunction<Tuple2<String, JSONObject>, Tuple2<String, JSONObject>, String, TimeWindow> {
@Override
public void apply(String key, TimeWindow timeWindow, Iterable<Tuple2<String, JSONObject>> iterable, Collector<Tuple2<String, JSONObject>> collector) throws Exception {
}
}
}