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From Simone Robutti <simone.robu...@radicalbit.io>
Subject Re: Java Maps and Type Information
Date Tue, 01 Mar 2016 20:45:59 GMT
I tried to simplify it to the bones but I'm actually defining a custom
MapFunction<java.util.Map<String,Object>,java.util.Map<String,Object>> that
even with a simple identity function fails at runtime giving me the
following error:

>Exception in thread "main"
org.apache.flink.api.common.functions.InvalidTypesException: The return
type of function 'main(Main.java:45)' could not be determined
automatically, due to type erasure. You can give type information hints by
using the returns(...) method on the result of the transformation call, or
by letting your function implement the 'ResultTypeQueryable' interface.

where the line 45 is the line where I invoke the map function.

Here the piece of code:

ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
        Map<String,Object> inputMap = new HashMap<String,Object>();

        MapFunction operator=new

            public Map<String, Object> map(Map<String, Object>
stringObjectMap) throws Exception {
                return stringObjectMap;

        List<Map<String, Object>> input = new LinkedList<>();
        DataSource<Map<String, Object>> dataset = env.fromCollection(input);
        List<java.util.Map<FieldName, Object>> collectedResult =

2016-03-01 16:42 GMT+01:00 Aljoscha Krettek <aljoscha@apache.org>:

> Hi,
> what kind of program are you writing? I just wrote a quick example using
> the DataStream API where I’m using Map<String, Tuple2<String, Integer>>
> the output type of one of my MapFunctions.
> Cheers,
> Aljoscha
> > On 01 Mar 2016, at 16:33, Simone Robutti <simone.robutti@radicalbit.io>
> wrote:
> >
> > Hello,
> >
> > to my knowledge is not possible to use a java.util.Map for example in a
> FlatMapFunction<java.util.Map, java.util.Map>. Is that correct? It gives a
> typer error at runtime and it doesn't work even with explicit
> TypeInformation hints.
> >
> > Is there any way to make it work?
> >
> > Thanks,
> >
> > Simone

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