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From Stephan Ewen <se...@apache.org>
Subject Re: Variable not initialized in the open() method of RichMapFunction
Date Fri, 22 Jul 2016 16:07:12 GMT
Initializing in "open(Configuration)" means that the ObjectMapper is
created only in the cluster once the MapFunction is started.

Otherwise it is created before (on the client) and Serialization-copied
into the cluster, together with the MapFunction.

If the second approach works well (i.e., the ObjectMapper is serialization
friendly), then there is no downside to it.

On Fri, Jul 22, 2016 at 6:01 PM, Dong iL, Kim <kim.same@gmail.com> wrote:

> declare objectMapper out of map class.
>
> final ObjectMapper objectMapper = new ObjectMapper();
>
> source.map(str -> objectMapper.readValue(value, Request.class));
>
> On Sat, Jul 23, 2016 at 12:28 AM, Yassin Marzouki <yassmarzou@gmail.com>
> wrote:
>
>> Thank you Stephan and Kim, that solved the problem.
>> Just to make sure, is using a MapFunction as in the following code any
>> different? i.e. does it initialize the objectMapper for every element in
>> the stream?
>>
>> .map(new MapFunction<String, Request>() {
>>
>>     private ObjectMapper objectMapper = new ObjectMapper();
>>
>>         @Override
>>              public Request map(String value) throws Exception {
>>                  return objectMapper.readValue(value, Request.class);
>>         }
>> })
>>
>> On Fri, Jul 22, 2016 at 5:20 PM, Dong iL, Kim <kim.same@gmail.com> wrote:
>>
>>> oops. stephan already answered.
>>> sorry. T^T
>>>
>>> On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <kim.same@gmail.com>
>>> wrote:
>>>
>>>> is open method signature right? or typo?
>>>>
>>>> void open(Configuration parameters) throws Exception;
>>>>
>>>> On Sat, Jul 23, 2016 at 12:09 AM, Stephan Ewen <sewen@apache.org>
>>>> wrote:
>>>>
>>>>> I think you overrode the open method with the wrong signature. The
>>>>> right signature would be "open(Configuration cfg) {...}". You probably
>>>>> overlooked this because you missed the "@Override" annotation.
>>>>>
>>>>> On Fri, Jul 22, 2016 at 4:49 PM, Yassin Marzouki <yassmarzou@gmail.com
>>>>> > wrote:
>>>>>
>>>>>> Hi everyone,
>>>>>>
>>>>>> I want to convert a stream of json strings to POJOs using Jackson,
so
>>>>>> I did the following:
>>>>>>
>>>>>> .map(new RichMapFunction<String, Request>() {
>>>>>>
>>>>>>     private ObjectMapper objectMapper;
>>>>>>
>>>>>>         public void open() {
>>>>>>             objectMapper = new ObjectMapper();
>>>>>>         }
>>>>>>
>>>>>>         @Override
>>>>>>              public Request map(String value) throws Exception {
>>>>>>                  return objectMapper.readValue(value, Request.class);
>>>>>>         }
>>>>>> })
>>>>>>
>>>>>> But this code gave me a NullPointerException because the objectMapper
>>>>>> was not initialized successfully.
>>>>>>
>>>>>> 1. Isn't the open() method supposed to be called before map() and
>>>>>> initialize objectMapper?
>>>>>> 2. I figured out that initializing objectMapper before the open()
>>>>>> method resolves the problem, and that it works also with a simple
>>>>>> MapFunction. In that case, is there an advantage for using a
>>>>>> RichMapFunction?
>>>>>>
>>>>>> Best,
>>>>>> Yassine
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> <A HREF="http://www.kiva.org" TARGET="_top">
>>>> <IMG SRC="http://www.kiva.org/images/bannerlong.png" WIDTH="460"
>>>> HEIGHT="60" ALT="Kiva - loans that change lives" BORDER="0"
>>>> ALIGN="BOTTOM"></A>
>>>>
>>>
>>>
>>>
>>> --
>>> <A HREF="http://www.kiva.org" TARGET="_top">
>>> <IMG SRC="http://www.kiva.org/images/bannerlong.png" WIDTH="460"
>>> HEIGHT="60" ALT="Kiva - loans that change lives" BORDER="0"
>>> ALIGN="BOTTOM"></A>
>>>
>>
>>
>
>
> --
> <A HREF="http://www.kiva.org" TARGET="_top">
> <IMG SRC="http://www.kiva.org/images/bannerlong.png" WIDTH="460"
> HEIGHT="60" ALT="Kiva - loans that change lives" BORDER="0"
> ALIGN="BOTTOM"></A>
>

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