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https://issues.apache.org/jira/browse/FLINK-3042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15470728#comment-15470728
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ASF GitHub Bot commented on FLINK-3042:
---------------------------------------
Github user greghogan commented on a diff in the pull request:
https://github.com/apache/flink/pull/2337#discussion_r77827675
--- Diff:
flink-core/src/main/java/org/apache/flink/api/common/typeinfo/TypeInfoFactory.java
---
@@ -0,0 +1,55 @@
+/*
+ * 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.api.common.typeinfo;
+
+import java.lang.reflect.Type;
+import java.util.Map;
+import org.apache.flink.annotation.Public;
+import org.apache.flink.api.java.typeutils.TypeExtractor;
+
+/**
+ * Base class for implementing a type information factory. A type
information factory allows for
+ * plugging-in user-defined {@link TypeInformation} into the Flink type
system. The factory is
+ * called during the type extraction phase if the corresponding type has
been annotated with
+ * {@link TypeInfo}. In a hierarchy of types the closest factory will be
chosen while traversing
+ * upwards, however, a globally registered factory has highest precedence
+ * (see {@link TypeExtractor#registerFactory(Type, Class)}).
+ *
+ * @param <T> type for which {@link TypeInformation} is created
+ */
+@Public
+public abstract class TypeInfoFactory<T> {
+
+ public TypeInfoFactory() {
+ // default constructor
--- End diff --
What is the reason for the empty no-arg constructor?
> Define a way to let types create their own TypeInformation
> ----------------------------------------------------------
>
> Key: FLINK-3042
> URL: https://issues.apache.org/jira/browse/FLINK-3042
> Project: Flink
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.10.0
> Reporter: Stephan Ewen
> Assignee: Timo Walther
> Fix For: 1.0.0
>
>
> Currently, introducing new Types that should have specific TypeInformation
> requires
> - Either integration with the TypeExtractor
> - Or manually constructing the TypeInformation (potentially at every place)
> and using type hints everywhere.
> I propose to add a way to allow classes to create their own TypeInformation
> (like a static method "createTypeInfo()").
> To support generic nested types (like Optional / Either), the type extractor
> would provide a Map of what generic variables map to what types (deduced from
> the input). The class can use that to create the correct nested
> TypeInformation (possibly by calling the TypeExtractor again, passing the Map
> of generic bindings).
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