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Date: Mon, 11 Sep 2017 03:38:55 -0700 (MST)
From: yunfan123 <yunfanfighting@foxmail.com>
To: user@flink.apache.org
Message-ID: <1505126335488-0.post@n4.nabble.com>
Subject: Keyed function type erasure problem.
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archived-at: Mon, 11 Sep 2017 10:39:06 -0000

Just small change from PojoExample:
PojoExample.java
<http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/file/t921/PojoExample.java>  
public class PojoExample<KEY> {
        private SelectorContainer<KEY> selectorContainer;
        // KeySelector class like this can't be used in flink !!!
	public static class SelectorContainer<K> implements KeySelector<Word ,K> {
		public KeySelector<Word, K> keySelector;
		public SelectorContainer(KeySelector<Word, K> keySelector) {
			this.keySelector = keySelector;
		}

		@Override
		public K getKey(Word value) throws Exception {
			return keySelector.getKey(value);
		}
	}
        public void run() {
              dataStream.keyed(selectorContainer);
        }
        
}

This will cause:
Type of TypeVariable 'K' in 'class
org.apache.flink.streaming.examples.wordcount.PojoExample$SelectorContainer'
could not be determined. This is most likely a type erasure problem. The
type extraction currently supports types with generic variables only in
cases where all variables in the return type can be deduced from the input
type(s).

org.apache.flink.api.java.typeutils.TypeExtractor.createTypeInfoWithTypeHierarchy(TypeExtractor.java:915)

org.apache.flink.api.java.typeutils.TypeExtractor.privateCreateTypeInfo(TypeExtractor.java:836)

org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:622)

org.apache.flink.api.java.typeutils.TypeExtractor.getKeySelectorTypes(TypeExtractor.java:443)

org.apache.flink.api.java.typeutils.TypeExtractor.getKeySelectorTypes(TypeExtractor.java:436)

org.apache.flink.streaming.api.datastream.KeyedStream.<init>(KeyedStream.java:108)

org.apache.flink.streaming.api.datastream.DataStream.keyBy(DataStream.java:263)

org.apache.flink.streaming.examples.wordcount.PojoExample.execute(PojoExample.java:86)

org.apache.flink.streaming.examples.wordcount.PojoExample.main(PojoExample.java:108)

It sames can't use a class contains the KeySelector ?



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