Re: Variable not initialized in the open() method of RichMapFunction

[Dong iL, Kim]

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 <yassmar...@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.s...@gmail.com> wrote:
>
>> oops. stephan already answered.
>> sorry. T^T
>>
>> On Sat, Jul 23, 2016 at 12:16 AM, Dong iL, Kim <kim.s...@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 <se...@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 <yassmar...@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
>>>>>
>>>>
>>>>
>>>
>>>
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>>
>>
>>
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>
>


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