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ASF GitHub Bot commented on FLINK-3708: --------------------------------------- Github user tillrohrmann commented on a diff in the pull request: https://github.com/apache/flink/pull/1905#discussion_r60400262 --- Diff: flink-libraries/flink-cep-scala/src/main/scala/org/apache/flink/cep/scala/PatternStream.scala --- @@ -0,0 +1,142 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.flink.cep.scala + +import java.util.{Map => JMap} +import org.apache.flink.api.common.typeinfo.TypeInformation +import org.apache.flink.cep.{PatternFlatSelectFunction, PatternSelectFunction, PatternStream => JPatternStream} +import org.apache.flink.streaming.api.scala._ +import org.apache.flink.util.Collector +import scala.reflect.ClassTag + +/** + * Stream abstraction for CEP pattern detection. A pattern stream is a stream which emits detected + * pattern sequences as a map of events associated with their names. The pattern is detected using a + * { @link org.apache.flink.cep.nfa.NFA}. In order to process the detected sequences, the user + * has to specify a { @link PatternSelectFunction} or a { @link PatternFlatSelectFunction}. + * + * @param jPatternStream Underlying pattern stream from Java API + * @tparam T Type of the events + */ +class PatternStream[T: TypeInformation : ClassTag](jPatternStream: JPatternStream[T]) { + + private[flink] def getWrappedPatternStream = jPatternStream + + /** + * Applies a select function to the detected pattern sequence. For each pattern sequence the + * provided { @link PatternSelectFunction} is called. The pattern select function can produce + * exactly one resulting element. + * + * @param patternSelectFunction The pattern select function which is called for each detected + * pattern sequence. + * @tparam R Type of the resulting elements + * @return { @link DataStream} which contains the resulting elements from the pattern select + * unction. + */ + def select[R: TypeInformation : ClassTag](patternSelectFunction: PatternSelectFunction[T, R]): DataStream[R] = { + asScalaStream(jPatternStream.select(patternSelectFunction, implicitly[TypeInformation[R]])) + } + + /** + * Applies a flat select function to the detected pattern sequence. For each pattern sequence + * the provided { @link PatternFlatSelectFunction} is called. The pattern flat select function + * can produce an arbitrary number of resulting elements. + * + * @param patternFlatSelectFunction The pattern flat select function which is called for each + * detected pattern sequence. + * @tparam R Type of the resulting elements + * @return { @link DataStream} which contains the resulting elements from the pattern flat select + * function. + */ + def flatSelect[R: TypeInformation : ClassTag](patternFlatSelectFunction: PatternFlatSelectFunction[T, R]): DataStream[R] = { + asScalaStream(jPatternStream.flatSelect(patternFlatSelectFunction, implicitly[TypeInformation[R]])) + } + + /** + * Applies a select function to the detected pattern sequence. For each pattern sequence the + * provided { @link PatternSelectFunction} is called. The pattern select function can produce + * exactly one resulting element. + * + * @param patternSelectFun The pattern select function which is called for each detected + * pattern sequence. + * @tparam R Type of the resulting elements + * @return { @link DataStream} which contains the resulting elements from the pattern select + * function. + */ + def select[R: TypeInformation : ClassTag](patternSelectFun: JMap[String, T] => R): DataStream[R] = { --- End diff -- I think it would be good to not give a Java `Map` but a Scala `Map` to the `patternSelectFun` as you've done in the out commented code. I think it would be good to use an explicit conversion via the `JavaConverters` and the `asScala` method. Semantically, it would be correct to provide a immutable map to the Scala lambda. However, this would mean that we copy the map. Therefore, for the sake of efficiency, we could simply pass in the result of the `asScala` call which is a mutable `Map`. > Scala API for CEP > ----------------- > > Key: FLINK-3708 > URL: https://issues.apache.org/jira/browse/FLINK-3708 > Project: Flink > Issue Type: Improvement > Components: CEP > Affects Versions: 1.1.0 > Reporter: Till Rohrmann > Assignee: Stefan Richter > > Currently, The CEP library does not support Scala case classes, because the > {{TypeExtractor}} cannot handle them. In order to support them, it would be > necessary to offer a Scala API for the CEP library. -- This message was sent by Atlassian JIRA (v6.3.4#6332)