Re: Java Maps and Type Information
Hi, what kind of program are you writing? I just wrote a quick example using the DataStream API where I’m using Map> as the output type of one of my MapFunctions. Cheers, Aljoscha > On 01 Mar 2016, at 16:33, Simone Robutti wrote: > > Hello, > > to my knowledge is not possible to use a java.util.Map for example in a > FlatMapFunction. 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
Re: Java Maps and Type Information
I tried to simplify it to the bones but I'm actually defining a custom
MapFunction,java.util.Map> 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();
env.setParallelism(2);
Map inputMap = new HashMap();
inputMap.put("sepal_width",2.0);
inputMap.put("sepal_length",2.0);
inputMap.put("petal_width",2.0);
inputMap.put("petal_length",2.0);
MapFunction operator=new
MapFunction,Map>(){
@Override
public Map map(Map
stringObjectMap) throws Exception {
return stringObjectMap;
}
};
List> input = new LinkedList<>();
input.add(inputMap);
DataSource> dataset = env.fromCollection(input);
List> collectedResult =
dataset.map(operator).collect();
2016-03-01 16:42 GMT+01:00 Aljoscha Krettek :
> Hi,
> what kind of program are you writing? I just wrote a quick example using
> the DataStream API where I’m using Map> as
> the output type of one of my MapFunctions.
>
> Cheers,
> Aljoscha
> > On 01 Mar 2016, at 16:33, Simone Robutti
> wrote:
> >
> > Hello,
> >
> > to my knowledge is not possible to use a java.util.Map for example in a
> FlatMapFunction. 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
>
>
Re: Java Maps and Type Information
Ok, I made it work but there's still an issue. I used
.returns(java.util.Map.class) after the "map" call and it works with this
simple function but it doesn't compile with my CustomMapFunction that
extends MapFunction. It gives a compilation error on the .returns() call.
This is the case only if the variable operator is of type CustomMapFunction
but if I do
> MapFunction operator = new CustomMapFunction();
it works again.
If I go back to
> CustomMapFunction operator = new CustomMapFunction();
it gives this error:
>Error:(43, 87) java: no suitable method found for
returns(java.lang.Class)
method
Should I open an issue?
2016-03-01 21:45 GMT+01:00 Simone Robutti :
> I tried to simplify it to the bones but I'm actually defining a custom
> MapFunction,java.util.Map> 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();
> env.setParallelism(2);
> Map inputMap = new HashMap();
> inputMap.put("sepal_width",2.0);
> inputMap.put("sepal_length",2.0);
> inputMap.put("petal_width",2.0);
> inputMap.put("petal_length",2.0);
>
> MapFunction operator=new
> MapFunction,Map>(){
>
> @Override
> public Map map(Map
> stringObjectMap) throws Exception {
> return stringObjectMap;
> }
> };
>
> List> input = new LinkedList<>();
> input.add(inputMap);
> DataSource> dataset =
> env.fromCollection(input);
> List> collectedResult =
> dataset.map(operator).collect();
>
>
>
>
> 2016-03-01 16:42 GMT+01:00 Aljoscha Krettek :
>
>> Hi,
>> what kind of program are you writing? I just wrote a quick example using
>> the DataStream API where I’m using Map> as
>> the output type of one of my MapFunctions.
>>
>> Cheers,
>> Aljoscha
>> > On 01 Mar 2016, at 16:33, Simone Robutti
>> wrote:
>> >
>> > Hello,
>> >
>> > to my knowledge is not possible to use a java.util.Map for example in a
>> FlatMapFunction. 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
>>
>>
>
Re: Java Maps and Type Information
I’m afraid so, yes. I also tried out your example and it works if I add a .returns() after the .map() (as you did). Somehow the TypeExtractor seems to be acting up. > On 02 Mar 2016, at 11:12, Simone Robutti wrote: > > >Error:(43, 87) java: no suitable method found for > >returns(java.lang.Class) > method
