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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3708) Scala API for CEP
Date Thu, 21 Apr 2016 08:24:25 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15251547#comment-15251547
] 

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_r60542216
  
    --- Diff: flink-libraries/flink-cep-scala/src/main/scala/org/apache/flink/cep/scala/pattern/package.scala
---
    @@ -0,0 +1,42 @@
    +/*
    + * 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 org.apache.flink.cep.pattern.{FollowedByPattern => JFollowedByPattern, Pattern
=> JPattern}
    +
    +import _root_.scala.reflect.ClassTag
    +
    +package object pattern {
    +  /**
    +    * Utility method to wrap { @link org.apache.flink.cep.pattern.Pattern} and its subclasses
    +    * for usage with the Scala API.
    +    *
    +    * @param javaPattern The underlying pattern from the Java API
    +    * @tparam T Base type of the elements appearing in the pattern
    +    * @tparam F Subtype of T to which the current pattern operator is constrained
    +    * @return A pattern from the Scala API which wraps the pattern from the Java API
    +    */
    +  private[flink] def wrapPattern[
    +  T: ClassTag, F <: T : ClassTag](javaPattern: JPattern[T, F])
    +  : Pattern[T, F] = javaPattern match {
    +    case f: JFollowedByPattern[T, F] => FollowedByPattern[T, F](f)
    +    case p: JPattern[T, F] => Pattern[T, F](p)
    +    case _ => null
    --- End diff --
    
    Oh yes, you're totally right Stefan. But then we could maybe return an `Option[Pattern]`
from the `wrapPattern` method.


> 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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