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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3708) Scala API for CEP
Date Wed, 20 Apr 2016 12:43:25 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15249797#comment-15249797
] 

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_r60399432
  
    --- 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] = {
    +    val patternSelectFunction: PatternSelectFunction[T, R] = new PatternSelectFunction[T,
R] {
    +      val cleanFun = cleanClosure(patternSelectFun)
    +
    +      def select(in: JMap[String, T]): R = cleanFun(in)
    +    }
    +    select(patternSelectFunction)
    +  }
    +
    +  //  def select[R: TypeInformation : ClassTag](patternSelectFun: Map[String, T] =>
R): DataStream[R] = {
    +  //    val patternSelectFunction: PatternSelectFunction[T, R] = new PatternSelectFunction[T,
R] {
    +  //      val cleanFun = cleanClosure(patternSelectFun)
    +  //
    +  //      def select(in: JMap[String, T]): R = cleanFun(in.toMap)
    +  //    }
    +  //    select(patternSelectFunction)
    +  //  }
    +
    +  //TODO ask about implicit conversion between Java Map and Scala Map
    +  /**
    +    * 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 patternFlatSelectFun 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](patternFlatSelectFun: (JMap[String, T],
Collector[R]) => Unit): DataStream[R] = {
    +    val patternFlatSelectFunction: PatternFlatSelectFunction[T, R] = new PatternFlatSelectFunction[T,
R] {
    +      val cleanFun = cleanClosure(patternFlatSelectFun)
    +
    +      def flatSelect(pattern: JMap[String, T], out: Collector[R]): Unit = cleanFun(pattern,
out)
    +    }
    +    flatSelect(patternFlatSelectFunction)
    +  }
    +
    +  //  def flatSelect[R: TypeInformation : ClassTag](patternFlatSelectFun: (Map[String,
T], Collector[R]) => Unit): DataStream[R] = {
    +  //    val patternFlatSelectFunction: PatternFlatSelectFunction[T, R] = new PatternFlatSelectFunction[T,
R] {
    +  //      val cleanFun = cleanClosure(patternFlatSelectFun)
    +  //
    +  //      def flatSelect(pattern: JMap[String, T], out: Collector[R]): Unit = cleanFun(pattern.toMap,
out)
    +  //    }
    +  //    flatSelect(patternFlatSelectFunction)
    +  //  }
    +
    +}
    +
    +object PatternStream {
    +  //TODO ask construction
    +  /**
    +    *
    +    * @param jPatternStream Underlying pattern stream from Java API
    +    * @tparam T Type of the events
    +    * @return A new pattern stream wrapping the pattern stream from Java APU
    +    */
    +  def apply[T: TypeInformation : ClassTag](jPatternStream: JPatternStream[T]) = {
    +    new PatternStream[T](jPatternStream)
    +  }
    +}
    --- End diff --
    
    `ClassTags` are not needed for functions.


> 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.



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