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https://issues.apache.org/jira/browse/FLINK-3708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15249819#comment-15249819
]
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_r60400970
--- Diff:
flink-libraries/flink-cep-scala/src/main/scala/org/apache/flink/cep/scala/package.scala
---
@@ -0,0 +1,49 @@
+/*
+ * 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
+
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.scala.ClosureCleaner
+import org.apache.flink.cep.{PatternStream => JPatternStream}
+
+import _root_.scala.reflect.ClassTag
+
+package object scala {
+
+ /**
+ * Utility method to wrap { @link org.apache.flink.cep.PatternStream}
+ * for usage with the Scala API.
+ *
+ * @param javaPatternStream The underlying pattern stream from the Java
API
+ * @tparam T Type of the events
+ * @return A pattern stream from the Scala API which wraps a pattern
stream from the Java API
+ */
+ private[flink] def wrapPatternStream[T: TypeInformation :
ClassTag](javaPatternStream: JPatternStream[T])
+ : scala.PatternStream[T] = {
+ javaPatternStream match {
+ case p: JPatternStream[T] => PatternStream[T](p)
+ case _ => null
--- End diff --
I think we should throw an `Exception` if we encounter a `null` value here.
The reason is that the subsequent operations would throw a
`NullPointerException` otherwise. Moreover, there is no good strategy how to
continue with a `null` pattern stream.
The most scalaesque way would be:
```
Option(javaPatternStream) match {
case Some(p) => PatternStream[T](p)
case None => throw new Exception(...)
}
```
> 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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