[jira] [Created] (FLINK-2557) Manal type information via "returns" fails in DataSet API

[Matthias J. Sax (JIRA)]

Matthias J. Sax created FLINK-2557:
--------------------------------------

             Summary: Manal type information via "returns" fails in DataSet API
                 Key: FLINK-2557
                 URL: https://issues.apache.org/jira/browse/FLINK-2557
             Project: Flink
          Issue Type: Bug
          Components: Java API
            Reporter: Matthias J. Sax


I changed the WordCount example as below and get an exception:

Tokenizer is change to this (removed generics and added cast to String):

{code:java}
public static final class Tokenizer implements FlatMapFunction {
        public void flatMap(Object value, Collector out) {
                String[] tokens = ((String) value).toLowerCase().split("\\W+");
                for (String token : tokens) {
                        if (token.length() > 0) {
                                out.collect(new Tuple2<String, Integer>(token, 
1));
                        }
                }
        }
}
{code}

I added call to "returns(....)" here:

{code:java}
DataSet<Tuple2<String, Integer>> counts =
  text.flatMap(new Tokenizer()).returns("Tuple2<String,Integer>")
  .groupBy(0).sum(1);
{code}

The exception is:

{noformat}
Exception in thread "main" java.lang.IllegalArgumentException: The types of the 
interface org.apache.flink.api.common.functions.FlatMapFunction could not be 
inferred. Support for synthetic interfaces, lambdas, and generic types is 
limited at this point.
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getParameterType(TypeExtractor.java:686)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getParameterTypeFromGenericType(TypeExtractor.java:710)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getParameterType(TypeExtractor.java:673)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.privateCreateTypeInfo(TypeExtractor.java:365)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:279)
        at 
org.apache.flink.api.java.typeutils.TypeExtractor.getFlatMapReturnTypes(TypeExtractor.java:120)
        at org.apache.flink.api.java.DataSet.flatMap(DataSet.java:262)
        at 
org.apache.flink.examples.java.wordcount.WordCount.main(WordCount.java:69)
{noformat}

Fix:
This should not immediately fail, but also only give a
"MissingTypeInfo" so that type hints would work.

The error message is also wrong, btw: It should state that raw types are
not supported.



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