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`.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
